[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++

[Launchpad Bug Tracker]

*** This bug is a duplicate of bug 1510042 ***
https://bugs.launchpad.net/bugs/1510042

This bug was fixed in the package llvm-toolchain-3.8 - 1:3.8.1-7ubuntu2

---
llvm-toolchain-3.8 (1:3.8.1-7ubuntu2) yakkety; urgency=medium

  * Ignore test results on i386, as done on any other architecture.
  * Don't use gold on powerpc, not supporting secure-plt.

 -- Matthias Klose   Sun, 07 Aug 2016 12:45:46 +0200

** Changed in: llvm-toolchain-3.8 (Ubuntu)
   Status: Confirmed => Fix Released

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed
Status in llvm-toolchain-3.8 package in Ubuntu:
  Fix Released

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++

[Daniel van Vugt]

*** This bug is a duplicate of bug 1510042 ***
https://bugs.launchpad.net/bugs/1510042

** This bug has been marked a duplicate of bug 1510042
   clang++ no longer ABI-compatible with g++

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed
Status in llvm-toolchain-3.8 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: llvm-toolchain-3.8 (Ubuntu)
   Status: New => Confirmed

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You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed
Status in llvm-toolchain-3.8 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++

[Mathew Hodson]

** Changed in: llvm-toolchain-3.8 (Ubuntu)
   Importance: Undecided => High

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed
Status in llvm-toolchain-3.8 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++

[Jeremy Bicha]

** Also affects: llvm-toolchain-3.8 (Ubuntu)
   Importance: Undecided
   Status: New

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed
Status in llvm-toolchain-3.8 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++

[Ubuntu Foundations Team Bug Bot]

The attachment "clang-3.8-abi_tag-ubuntu-changes.diff" seems to be a
debdiff.  The ubuntu-sponsors team has been subscribed to the bug report
so that they can review and hopefully sponsor the debdiff.  If the
attachment isn't a patch, please remove the "patch" flag from the
attachment, remove the "patch" tag, and if you are member of the
~ubuntu-sponsors, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by
~brian-murray, for any issue please contact him.]

** Tags added: patch

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++

[the paul]

I've made a first pass at adapting patches D17567 and D18035 to work
with your clang-3.8 packages. It builds and passes its own build-time
tests, and successfully builds and links a medium-size project we have
at work on 16.04, but I can't vouch for it much more than that.

I can see that this particular bug is attached to llvm-toolchain-3.6 and
not 3.8, but there doesn't seem to be a corresponding bug on 3.8, so
hopefully this isn't a bad place to mention it. Haven't tried patching
clang-3.6 yet.

** Patch added: "clang-3.8-abi_tag-ubuntu-changes.diff"
   
https://bugs.launchpad.net/ubuntu/+source/llvm-toolchain-3.6/+bug/1488254/+attachment/4703637/+files/clang-3.8-abi_tag-ubuntu-changes.diff

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++

[Christian Convey]

Hi guys,

Anyone know when we might see this fix make it into Ubuntu 16.04's
official repos?  I'm doing some app development that's hindered by this
bug.

(If there's a better forum for this question, I'd be grateful for a
redirect.)

Thanks very much,
Christian

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Dmitry-polukhin]

abi_tag implementation was committed to Clang
http://reviews.llvm.org/D18035 Please start testing on your apps and
report issues.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

FWIW, Arch has applied both patches (as Andrey has stated in comment 37)
and it is working fine.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Mclow-lists]

Sounds like a chance for people to install the patch locally and start
using it, and then provide feedback on any problems that crop up.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Tim Jones]

I've been using the patched version for the past couple of days, no
issues so far.

But, I'm not one of the developers and don't know this code base and
just because it *seems* to work doesn't mean it's correct yet. I'm just
going to continue with what works well enough for me at the moment, with
patience.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Giacomopoz]

(In reply to comment #63)
> Hi, any chance of an ETA guestimate / status update?
> 
> Cheers,
> Tim

The status is that there is a patch ready since 23rd March
http://reviews.llvm.org/D18035#381281 and the author (and all users) is
waiting for feedback from developers and/or for the patch to be merged.

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Tim Jones]

Hi, any chance of an ETA guestimate / status update?

Cheers,
Tim

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You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Syniurge]

This is becoming more and more of an important issue as distributions
switch to building all their packages against GCC + libstdc++ 5 and
plaster their libraries with [abi:cxx11] tags.

Since Ubuntu 15.10 Clang is basically unusable, every library making use
of std::string has to be recompiled with -D_GLIBCXX_USE_CXX11_ABI=0, or
with GCC/libstdc++ 4.9 in order to prevent linking errors.

Surprising that Dmitry's patch isn't receiving more attention.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Dmitry-polukhin]

My patch for Sema part with of the attribute under review is here
http://reviews.llvm.org/D17567

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
https://bugs.launchpad.net/llvm/+bug/1488254/+subscriptions

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[Desktop-packages] [Bug 1488254]

[Renato Golin]

(In reply to comment #58)
> Jason Merrill said he'd write up some brief documentation for the attribute.
> We'd like to work from that rather than trying to guess GCC's intent from
> examples.

That's most helpful, thanks!

What about Dmitry's patch?

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
https://bugs.launchpad.net/llvm/+bug/1488254/+subscriptions

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[Desktop-packages] [Bug 1488254]

[Dmitry-polukhin]

Status update:
- Sema part was committed http://reviews.llvm.org/D17567
- Mangler part was sent for review http://reviews.llvm.org/D18035

Best regards,
Dmitry
==
Software Engineer
Intel Compiler Team

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Richard-llvm]

Jason Merrill said he'd write up some brief documentation for the
attribute. We'd like to work from that rather than trying to guess GCC's
intent from examples.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Giacomopoz]

did this issue hit another roadblock ?

-- 
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[David-abdurachmanov]

More bug-fixing for abi_tag on GCC side: https://gcc.gnu.org/ml/gcc-
patches/2016-02/msg01293.html

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Jverg]

(In reply to comment #39)
> Moreover, FreeBSD had to take many short-cuts to get rid of libstdc++ on the
> base system, including making symlinks named after GNU libraries and tools
> to LLVM libraries and tools, and the mapping is NOT 1-to-1. See the libc++ +
> compiler-rt + libunwind vs. libgcc + libgcc_s + libgcc_eh connundrum.

There are not that many short-cuts and the primary issue was the desire
to allow libstdc++ and libc++ to coexist. If it was just about using
libc++, the issue is much simpler.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Dmitry-polukhin]

Hi Stefan,

This is an important issue in Clang and I would like to move on with
patch http://reviews.llvm.org/D12834 (also see my last comment there).
If you don't mind, I'll get your patch split it into smaller patches and
start resolving reviewers comments. Please let me know if you have
cycles and would like to keep working on this patch yourself.

Best regards,
Dmitry
==
Software Engineer
Intel Compiler Teaml

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You received this bug notification because you are a member of Desktop
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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

Hi Dmitry,

(In reply to comment #53)
> Hi Stefan,
> 
> This is an important issue in Clang and I would like to move on with patch
> http://reviews.llvm.org/D12834 (also see my last comment there). If you
> don't mind, I'll get your patch split it into smaller patches and start
> resolving reviewers comments. Please let me know if you have cycles and
> would like to keep working on this patch yourself.

I agree it is important, and it saddens me not having more time for
this.

I'm perfectly fine with you (and others) taking this over - thanks!

regards,
Stefan

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You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

Hum, both sound like serious bugs. I'm surprised all distros bought in
the new ABI so eagerly.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

Hi Andrey,

(In reply to comment #45)
> Stefan [Bühler], do you plan to finish work on the patch? Do you need help
> with code review? (I just added Aaron Ballman, who is code owner for
> attributes).

I think the attributes part of the patch is quite good compared with
the mangling part... perhaps it should be split into a separate patch.

Regarding the mangling I'm not too happy with my patch. I don't understand 
what most of the mangling code did before to actually know where 
to insert the tagging code. This is C++ on a level I don't usually touch;
I'm not familiar with all the terms (,
, ...) and just keep guessing what they do.

Also I don't like using recursion to determine the inherited abi tags;
I think using temporary strings instead of directly writing to the stream
would solve this.

All in all I hoped to get some feedbacks how things are done or should
look like; I don't mind if someone else wants to take over and rewrite
the mangling :)

I planned looking at the original gcc code some day, but didn't get around
doing that either; maybe others can help with the documentation too (how
the abi tag mangling actually should look like). More "examples" certainly
wouldn't hurt either.

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You received this bug notification because you are a member of Desktop
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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Dmitry-polukhin]

I'll take a look to the change and will investigate why tests fail on
the proposed patch. Failing tests are not abi_tag specific so it should
be no changes on them.

Best regards,
Dmitry
==
Software Engineer
Intel Compiler Team

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Andreybokhanko]

Hi Stefan,

(In reply to comment #47)
> I think the attributes part of the patch is quite good compared with
> the mangling part... perhaps it should be split into a separate patch.
> 
> Regarding the mangling I'm not too happy with my patch. I don't understand 
> what most of the mangling code did before to actually know where 
> to insert the tagging code. This is C++ on a level I don't usually touch;
> I'm not familiar with all the terms (,
> , ...) and just keep guessing what they do.
> 
> Also I don't like using recursion to determine the inherited abi tags;
> I think using temporary strings instead of directly writing to the stream
> would solve this.
> 
> All in all I hoped to get some feedbacks how things are done or should
> look like; I don't mind if someone else wants to take over and rewrite
> the mangling :)

Sure -- I will ask someone from Intel compiler team to handle mangling
part. We are co-located with Intel GCC team, so it's easy for us to ask
on intricacies of GCC implementation. :-)

I don't see attribute part of the patch to be reviewed, though -- we can
help with this as well. (Though the real authority to approve it belongs
to Aaron, so it's better to wait for his review (and ping if there is no
reply from his after a week)).

Yours,
Andrey

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[David-abdurachmanov]

"C++ PATCHes for abi_tag bugs" from Jason landed on gcc-patches, might
be relevant.

https://gcc.gnu.org/ml/gcc-patches/2016-01/msg02374.html

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Yaron-keren]

*** Bug 26401 has been marked as a duplicate of this bug. ***

-- 
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Yaron-keren]

Happens with clang-compiled objects attempting to use gcc-5 precompiled
packages such as boost, on Ubuntu 15.10, leading to

undefined reference to
`_ZN5boost9unit_test9ut_detail24normalize_test_case_nameENS0_13basic_cstringIKcEE'

where normalize_test_case_name returns std:string.

  std::string normalize_test_case_name( const_string name )

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Andreybokhanko]

Stefan [Bühler], do you plan to finish work on the patch? Do you need
help with code review? (I just added Aaron Ballman, who is code owner
for attributes).

Yours,
Andrey
==
Software Engineer
Intel Compiler Team
Intel

-- 
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

(In reply to comment #38)
> I said *tagged* return types, i.e. only those which need to break the ABI
> anyway.

Good point. Thanks for the distinction.


> The new ABI requires the full gcc abi-tag support to be compatible with
> gcc. If you compile everything with clang and disable dual ABI support
> you can get away with less, but what is the point? Just use the clang
> libc++ instead, which requires no changes.

I'm afraid it's not that simple. GNU libraries are the default on all
Linux (and other) distributions, and mixing libc++ with libstdc++ is
bound to create at least as many problems as it solves.

Moreover, FreeBSD had to take many short-cuts to get rid of libstdc++ on
the base system, including making symlinks named after GNU libraries and
tools to LLVM libraries and tools, and the mapping is NOT 1-to-1. See
the libc++ + compiler-rt + libunwind vs. libgcc + libgcc_s + libgcc_eh
connundrum.

We need libc++ to work on the supported architectures with and without
GNU libraries. Getting rid of the GNU counterparts is out of the
question for any practical purpose.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Hfinkel]

(In reply to comment #43)
> (In reply to comment #42)
> > OpenMandriva has successfully changed the compiler to clang (3.7.1 for now,
> > will update to 3.8 as it is released), but decided to stick with libstdc++
> > to preserve binary compatibility with other Linux distributions -- users
> > want to run non-open source stuff like steam, and that stuff doesn't get
> > built for OSes that don't have a giant user base.
> 
> If you ship GCC at all, and if that happens to be 5.x, and you happen to
> choose to enable the CXX11 ABI by default, you'll run into the exact same
> problem. Doesn't matter who's on top.
> 
> 
> > OpenMandriva could switch system libraries etc. to libc++, but even then
> > problems would likely arise (e.g. binary-only application links to Qt and
> > expects Qt to be linked to libstdc++ -- the only "fix" would be providing 2
> > different versions of all C++ libraries and even then things would likely
> > break, with e.g. libstdc++-Qt not being able to load style plugins built for
> > libc++-Qt and vice versa, so custom installed widget themes wouldn't work
> > for binary-only applications).
> 
> That, in addition to multilib/multiarch will be a major pain for all
> distros. This really isn't a solution.
> 
> 
> > So yes, there indeed is a use case for building the entire OS with clang but
> > not libc++ until we get to a point where relevant closed source stuff
> > switches to libc++ (or better yet, gets open sourced so people can link it
> > to any STL they like).
> 
> Even if the day Clang and libc++ become the top dog on most Linux
> distributions ever comes, we'll still have to cope with legacy GCC and
> libstdc++ for a good number of decades from then on.
> 
> Coexisting is the only solution for this century.

As a practical manner, we'll never be able to compile all of our
existing code against libc++, unless libc++ decides to implement the
not-insignificant set of libstdc++ extensions (e.g. everything under
__gnu_parallel::, _gnu_cxx::stdio_filebuf)
[https://gcc.gnu.org/onlinedocs/libstdc++/manual/extensions.html].

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

(In reply to comment #33)
> I really see no option in this; if the return type is tagged, the tag must be
> present in the signature somehow, or you can never mix different ABIs in the
> same binary.

This was probably already discussed, but if you mangle the return type,
how can you mix this with previous mangling?

Say, you have:

int foo(int);

Old mangling would give you _Z3fooi. Then you add:

double foo(int);

With old mangling, you get an error. With new mangling (mixed with old
mangling), you end up with three names. Say we mangle it before the
function name:

_Z3fooi, _Z3ifooi, _Z3dfooi

Now, it's clear that _Z3fooi needs to be an alias to one of the other
two, the question I can't answer is which one?

If you don't mix ABIs, then you only have two symbols and there is no
problem.

And how different from this did GCC implement their mangling and why is
it worse?

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

(In reply to comment #34)
> (In reply to comment #33)
> > I really see no option in this; if the return type is tagged, the tag must 
> > be
> > present in the signature somehow, or you can never mix different ABIs in the
> > same binary.
> 
> This was probably already discussed, but if you mangle the return type, how
> can you mix this with previous mangling?
> [...]

I said *tagged* return types, i.e. only those which need to break the
ABI anyway.

> And how different from this did GCC implement their mangling and why is it
> worse?

(Also see my previous post)

- if the return (or variable) type is tagged, tag the function (or variable)
- if the tag is already present in other places in the name (say
  function arguments), it is not added
- depending on the context it might not be added at all (nested functions,
  special symbols). very complex rules.
- for more details see my patch (has some docs), if you want to see some
  examples: http://files.stbuehler.de/test-itanium-mangle.html

(In reply to comment #35)
> I really think that implementing the full gcc abi-tag support is not 
> feasible for Clang. 
> So I would recommend to focus on compatibility with the single (new) ABI
> alone.
> 
> Distros that use the new ABI have recompiled all their C++ libraries,
> so there isn't much need for the dual ABI anyway.

The new ABI requires the full gcc abi-tag support to be compatible with
gcc. If you compile everything with clang and disable dual ABI support
you can get away with less, but what is the point? Just use the clang
libc++ instead, which requires no changes.

> (After all the ABI tags are just a tool to help with the transition.)

And a tool to help with future transitions (and in any other c++
libraries too). A nice tool, I might add, just not very well designed.

> But this is all that's needed. Just change the mangling of the affected
> return (and variable) types and you're set.

Please take a look at the examples (above), which need to work to make
clang compatible with gcc.
There is no shortcut.

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Octoploid]

(In reply to comment #33)
> (In reply to comment #32)
> > (In reply to comment #31)
> > > (In reply to comment #28)
> > > > The incompatibility was introduced by gcc's "automatic tagging of 
> > > > functions
> > > > and variables with tagged types where the tags are not already 
> > > > reflected in
> > > > the mangled name". 
> > > > 
> > > > Now every library function with e.g a std::string return type causes 
> > > > linker
> > > > errors.
> > > > 
> > > > To solve this issue, Clang only would have to implement the return type 
> > > > ABI
> > > > tagging. All other ABI tags are irrelevant AFAIK.
> > > 
> > > The change was necessary to support dual-abi in one binary; you need to
> > > be able to distinguish different ABIs in the return type.
> > 
> > No, the "automatic tagging of function return types" was unnecessary. The 
> > new
> > ABI was working perfectly fine with both compilers before that change.
> 
> As long as you keep the ABIs completely separated it works, yes.
> 
> To get basic dual ABI support you could require manual tagging of all
> functions
> which need tags (like, say, `std::string std::to_string(int)`) - but such
> procedure would be way too much work and error prone.
> 
> Especially if you have third party libraries providing such functions (like
> boost),
> which certainly would not start manual tagging, the linker could let you use
> functions you really must not use.

I really think that implementing the full gcc abi-tag support is not 
feasible for Clang. 
So I would recommend to focus on compatibility with the single (new) ABI alone.

Distros that use the new ABI have recompiled all their C++ libraries,
so there isn't much need for the dual ABI anyway.

(After all the ABI tags are just a tool to help with the transition.)

> I really see no option in this; if the return type is tagged, the tag must be
> present in the signature somehow, or you can never mix different ABIs in the
> same binary.
> 
> (I would have preferred to simply make tagged return (and variable!) types
> part
> of the name, which would have been straightforward compared to the mess GCC
> implemented: if the tag is already present in certain places, it is not
> added,
> depending on the context it might not be added at all, ...)

But this is all that's needed. Just change the mangling of the affected
return (and variable) types and you're set.

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Octoploid]

(In reply to comment #31)
> (In reply to comment #26)
> > (In reply to comment #25)
> > > 3. The problem only started because distros have chosen GCC 5 as their
> > > default compilers for the current releases, which defaults to C++11.
> > 
> > No gcc-5 doesn't default to C++11 and the issue here has nothing to do with 
> > C++98 vs. C++11.
> > 
> > Please try to get the facts strait, before posting long misleading replies.
> 
> It is related to C++11; afaik one of the reasons to break the ABI was to
> become C++11 standard compliant; also the new classes are tagged
> "cxx11".

The new ABI is used for C++98 as well...

> (In reply to comment #28)
> > The incompatibility was introduced by gcc's "automatic tagging of functions
> > and variables with tagged types where the tags are not already reflected in
> > the mangled name". 
> > 
> > Now every library function with e.g a std::string return type causes linker
> > errors.
> > 
> > To solve this issue, Clang only would have to implement the return type ABI
> > tagging. All other ABI tags are irrelevant AFAIK.
> 
> "Only" sounds like it would be easy and obvious. Sadly, this is not a
> trivial problem.
> 
> The change was necessary to support dual-abi in one binary; you need to
> be able to distinguish different ABIs in the return type.

No, the "automatic tagging of function return types" was unnecessary. The new
ABI was working perfectly fine with both compilers before that change.

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Andrey Vihrov]

> FWIW, Clang and GCC are running very well on my Arch Linux with GCC 5.3.0
> and GLIBCXX_3.4.21.

That's because Arch Linux is applying the patch from this bug report:
https://projects.archlinux.org/svntogit/packages.git/tree/trunk/PKGBUILD?h=packages/llvm#n81

-- 
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

(In reply to comment #40)
> So you're saying there is a use case to compile everything with clang and
> libstdc++?

Unfortunately, no.

A reasonably common scenario will also be to use libc++ on user code
while having libstdc++ used on the core libraries (say, boost), and them
two interface appropriately, statically and dynamically linked. Same
with RT and libgcc.

Linux systems use GNU for everything as default. All packages are
compiled with GCC, Glibc, binutils, libstdc++, etc. Users installing
packages will end up getting GCC-mangled libraries. But I still want to
use Clang there, for special cases, performance reasons, diagnostics,
etc.

So, while in FreeBSD and Apple environments they can get rid of the GNU
side, Linux is a lot more fragmented. For better or worse, we still need
to be compatible with GCC 5 abi at all levels. Clang, libc++, compiler-
rt need to all be aware (not necessarily change much) of this new ABI
and what effects it'll have on them.

Some Linux distros are trying to change the compiler, but that has
proven a lot harder than it should, due to decades abusing of the same
bugs in one compiler alone. The new ABI change is just yet another added
to the pile.

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Bero-b]

OpenMandriva has successfully changed the compiler to clang (3.7.1 for
now, will update to 3.8 as it is released), but decided to stick with
libstdc++ to preserve binary compatibility with other Linux
distributions -- users want to run non-open source stuff like steam, and
that stuff doesn't get built for OSes that don't have a giant user base.

OpenMandriva could switch system libraries etc. to libc++, but even then
problems would likely arise (e.g. binary-only application links to Qt
and expects Qt to be linked to libstdc++ -- the only "fix" would be
providing 2 different versions of all C++ libraries and even then things
would likely break, with e.g. libstdc++-Qt not being able to load style
plugins built for libc++-Qt and vice versa, so custom installed widget
themes wouldn't work for binary-only applications).

So yes, there indeed is a use case for building the entire OS with clang
but not libc++ until we get to a point where relevant closed source
stuff switches to libc++ (or better yet, gets open sourced so people can
link it to any STL they like).

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

(In reply to comment #32)
> (In reply to comment #31)
> > (In reply to comment #28)
> > > The incompatibility was introduced by gcc's "automatic tagging of 
> > > functions
> > > and variables with tagged types where the tags are not already reflected 
> > > in
> > > the mangled name". 
> > > 
> > > Now every library function with e.g a std::string return type causes 
> > > linker
> > > errors.
> > > 
> > > To solve this issue, Clang only would have to implement the return type 
> > > ABI
> > > tagging. All other ABI tags are irrelevant AFAIK.
> > 
> > The change was necessary to support dual-abi in one binary; you need to
> > be able to distinguish different ABIs in the return type.
> 
> No, the "automatic tagging of function return types" was unnecessary. The new
> ABI was working perfectly fine with both compilers before that change.

As long as you keep the ABIs completely separated it works, yes.

To get basic dual ABI support you could require manual tagging of all functions
which need tags (like, say, `std::string std::to_string(int)`) - but such
procedure would be way too much work and error prone.

Especially if you have third party libraries providing such functions (like 
boost),
which certainly would not start manual tagging, the linker could let you use
functions you really must not use.

I really see no option in this; if the return type is tagged, the tag must be
present in the signature somehow, or you can never mix different ABIs in the
same binary.

(I would have preferred to simply make tagged return (and variable!) types part
of the name, which would have been straightforward compared to the mess GCC
implemented: if the tag is already present in certain places, it is not added,
depending on the context it might not be added at all, ...)

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Octoploid]

(In reply to comment #27)
> (In reply to comment #26)
> > No. It was implemented in April this year, shortly before the gcc-5 release.
> > I've pointed out compatibility issue immediately:
> > https://gcc.gnu.org/ml/gcc-patches/2015-04/msg00153.html
> (...)
> > The were no behavioral changes at all after that patch went in.
> 
> In the Linaro thread, Jim points out to the abi_tag patch from 2012. Your
> mention is about "significant changes to attribute abi_tag". I can't see how
> I was wrong.
> 
> 
> > No gcc-5 doesn't default to C++11 and the issue here has nothing to do with 
> > C++98 vs. C++11.
> > 
> > Please try to get the facts strait, before posting long misleading replies.
> 
> This is what most of the documentation, email threads and conversations I
> had seem to point at. If you have a different opinion, than by all means,
> please share your knowledge.
> 
> Saying "it has nothing to do with" doesn't explain what it has to do with.
> I'm happy to be proven wrong here, as long as we get all the facts on the
> table. This bug doesn't seem to provide strong facts either.

The incompatibility was introduced by gcc's "automatic tagging of functions and 
variables with tagged types where the tags are not already reflected in the 
mangled name". 
Before that patch (https://gcc.gnu.org/ml/gcc-patches/2015-03/msg01029.html)
both gcc and clang could use the new ABI without any problem.

Now every library function with e.g a std::string return type causes
linker errors.

To solve this issue, Clang only would have to implement the return type
ABI tagging. All other ABI tags are irrelevant AFAIK.

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You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

Following up on the Linaro Toolchain list[1], I found out a few facts:

1. This feature was implemented in GCC and libstdc++ in 2012, after
discussions on the cauldron with distro representatives.

2. The feature is poorly documented, and may have changed behaviour
until recently. I have no evidence of changes, is anyone does, please
update.

3. The problem only started because distros have chosen GCC 5 as their
default compilers for the current releases, which defaults to C++11.

4. The fact that GCC developers didn't liaise with Clang developers is a
shame, but understandable. The real issue here is the fact that distro
representatives took an executive decision to change the object layout
of core C++ classes in libstdc++ and to change the ABI without worrying
about other compilers.

If they has asked Clang folks about the ABI change, (and they did, see
this thread), they would have known that the ABI behaviour was poorly
documented and a moving target (as they did, look at this bug), and
should have taken the decision to mitigate the problems.

In this case, I'd expect distro folks to be the middle-men between GCC
and Clang and to make sure that both compilers work well on their new
releases. If you look at this bug and all of those that were marked as
duplicate, you'll see that both Debian and RedHat based distros knew
that Clang still didn't have the feature they needed and why.

True, we could have been more informative and made explicit every detail
on why it was hard to know what to implement, but as middle-men, I
expected distros to be more pro-active towards unification and less pro-
active towards changing the ABI.

[1] https://lists.linaro.org/pipermail/linaro-
toolchain/2016-January/005457.html

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You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Giacomopoz]

(In reply to comment #18)
> I'm not going to treat this as a release blocker as it's more of a feature
> request than a regression.

Since I upgraded to Ubuntu 15.10 I cannot build anymore with clang
projects that include Boost (Ubuntu ships boost 1.58) because of this
GCC 5 ABI changes.

The result is that I won't be able to use clang anymore till this issue
gets fixed, making this a blocking issue.

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[T-hans]

I'm not going to treat this as a release blocker as it's more of a
feature request than a regression.

I'd still be open to merge a fix for this (though it seems unlikely),
but I won't treat it as a blocker.

-- 
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Hfinkel]

(In reply to comment #23)
> This is a feature, not a bug. Features do not block releases.
> 
> It's a feature because it's new behaviour to be added to Clang, not a
> regression in an old behaviour. That GCC designed and implemented this and
> that Linux distributions took that and ran with it is irritating, but does
> not make it a release blocker.
> 
> Implementing a new feature is not a one line fix, it's not something that
> can be merged to the release branch quickly - it needs design (especially in
> this case!) and soak testing.
> 
> It's nigh-on impossible for this to be done for the release, and therefore
> it makes no sense to have it block the release IMHO.

James is right; we cannot block the release on the development of this
feature.

Also, if you'd like to express your support for the development of this
feature to the Clang/LLVM community, you'll need to do it on llvm-dev
/cfe-dev, not here.

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You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Stephan-bergmann-secondary]

(In reply to comment #27)
> (In reply to comment #26)
> > No gcc-5 doesn't default to C++11 and the issue here has nothing to do with 
> > C++98 vs. C++11.
> > 
> > Please try to get the facts strait, before posting long misleading replies.
> 
> This is what most of the documentation, email threads and conversations I
> had seem to point at. If you have a different opinion, than by all means,
> please share your knowledge.

The relevant issue is whether libstdc++'s _GLIBCXX_USE_CXX11_ABI is
enabled by default, see
.

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

(In reply to comment #42)
> OpenMandriva has successfully changed the compiler to clang (3.7.1 for now,
> will update to 3.8 as it is released), but decided to stick with libstdc++
> to preserve binary compatibility with other Linux distributions -- users
> want to run non-open source stuff like steam, and that stuff doesn't get
> built for OSes that don't have a giant user base.

If you ship GCC at all, and if that happens to be 5.x, and you happen to
choose to enable the CXX11 ABI by default, you'll run into the exact
same problem. Doesn't matter who's on top.


> OpenMandriva could switch system libraries etc. to libc++, but even then
> problems would likely arise (e.g. binary-only application links to Qt and
> expects Qt to be linked to libstdc++ -- the only "fix" would be providing 2
> different versions of all C++ libraries and even then things would likely
> break, with e.g. libstdc++-Qt not being able to load style plugins built for
> libc++-Qt and vice versa, so custom installed widget themes wouldn't work
> for binary-only applications).

That, in addition to multilib/multiarch will be a major pain for all
distros. This really isn't a solution.


> So yes, there indeed is a use case for building the entire OS with clang but
> not libc++ until we get to a point where relevant closed source stuff
> switches to libc++ (or better yet, gets open sourced so people can link it
> to any STL they like).

Even if the day Clang and libc++ become the top dog on most Linux
distributions ever comes, we'll still have to cope with legacy GCC and
libstdc++ for a good number of decades from then on.

Coexisting is the only solution for this century.

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

(In reply to comment #35)
> I really think that implementing the full gcc abi-tag support is not 
> feasible for Clang. 
> So I would recommend to focus on compatibility with the single (new) ABI
> alone.

Wait, are you suggesting we move *all* users of *all* operating systems
for *all* users of Clang and LLVM to change to the new GCC ABI because
it's easier for Linux distributions that happen to have prematurely
chosen to move?

This doesn't make sense...

Even if we segregate this for Linux only, which wouldn't be pretty,
we're still forcing *all* other Linux distributions that may want to
have a Clang package to move to the new GCC ABI just because other
distros have.

Still doesn't make sense...

FWIW, Clang and GCC are running very well on my Arch Linux with GCC
5.3.0 and GLIBCXX_3.4.21.

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

(In reply to comment #39)
> (In reply to comment #38)
> > The new ABI requires the full gcc abi-tag support to be compatible with
> > gcc. If you compile everything with clang and disable dual ABI support
> > you can get away with less, but what is the point? Just use the clang
> > libc++ instead, which requires no changes.
> 
> [...]
> 
> We need libc++ to work on the supported architectures with and without GNU
> libraries. Getting rid of the GNU counterparts is out of the question for
> any practical purpose.

So you're saying there is a use case to compile everything with clang
and libstdc++? If that is actually something you need, and you don't
need to be compatible to any name mangling, you just need the part of
the patch in D12834 accepting abi tags and you should be fine (no dual
ABI support ofc); no modifications to the name mangling
(lib/AST/ItaniumMangle.cpp) are necessary for that.

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You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

(In reply to comment #26)
> (In reply to comment #25)
> > 3. The problem only started because distros have chosen GCC 5 as their
> > default compilers for the current releases, which defaults to C++11.
> 
> No gcc-5 doesn't default to C++11 and the issue here has nothing to do with 
> C++98 vs. C++11.
> 
> Please try to get the facts strait, before posting long misleading replies.

It is related to C++11; afaik one of the reasons to break the ABI was to
become C++11 standard compliant; also the new classes are tagged
"cxx11".


(In reply to comment #28)
> The incompatibility was introduced by gcc's "automatic tagging of functions
> and variables with tagged types where the tags are not already reflected in
> the mangled name". 
> 
> Now every library function with e.g a std::string return type causes linker
> errors.
> 
> To solve this issue, Clang only would have to implement the return type ABI
> tagging. All other ABI tags are irrelevant AFAIK.

"Only" sounds like it would be easy and obvious. Sadly, this is not a
trivial problem.

The change was necessary to support dual-abi in one binary; you need to
be able to distinguish different ABIs in the return type.

(In reply to comment #29)
> The relevant issue is whether libstdc++'s _GLIBCXX_USE_CXX11_ABI is enabled
> by default, see
> .

Yes. All distributions have the choice not to enable it by default in
the first place.


(In reply to comment #30)
> (In reply to comment #28)
> > To solve this issue, Clang only would have to implement the return type ABI
> > tagging. All other ABI tags are irrelevant AFAIK.
> 
> If I read correctly, one of the emails says this is only temporary, and
> wouldn't show in the final object, since C++ doesn't distinguish return
> types, that's most useful.

No, it is not temporary.

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Renato Golin]

(In reply to comment #19)
> But as I understood it, LLVM/Clang claims to support GCC
> and its libraries with a minimum version required.

I don't think we do. Our community has always sent a strong message that
we'll be compatible with what makes sense AND allows us enough time to
implement on our own.

> No user would expect there to be an maximum version requirement.

This doesn't make sense. We're not the same team, we can't possibly keep
up with another community entirely AND develop our own software at
instant speed.

If LLVM was a plugin to GCC, that could be true, but not *necessarily*
so. Since it's not, this statement doesn't make sense.


> I see two possible ways here for the next release:
> 1. State that LLVM/Clang only works up to GCC 4.9.

LLVM "is known to work" with GCC up to "M.N". We never claimed full
compatibility, nor I think we ever will.


> 2. Add this attribute to be compatible to the most recent GCC release (5.3)
> again.

If it was that simple, it would have been added already.

>From comments in this very thread, it seems GCC's own implementation had
several bugs, and implementing a bug for bug copy would be very silly
indeed.

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

(In reply to comment #28)
> The incompatibility was introduced by gcc's "automatic tagging of functions
> and variables with tagged types where the tags are not already reflected in
> the mangled name".

So, the original patch would allow the tagging, but this patch made it
automatic and compulsory?

I think one of the issues from the original patch is that we didn't need
it until it was made compulsory, and that decision was taken and there
was little discussion on the effects for Clang until this week, when all
release tests started failing.

This was a major cock-up from all of us (me included). I'm not trying to
blame people, just understand who should have what responsibility, so
that we make sure this doesn't happen again.


> Now every library function with e.g a std::string return type causes linker
> errors.

On AArch64, we don't always get linker errors, but we do get
segmentation fault on:

#include 
int main() { std::cout << "Hello World" << std::endl; }

On Debian unstable and I think the unreleased version of Ubuntu. RedHat,
Suse and others may have the same trouble. I was told this was related
to the same ABI tag problem, and reading that they've also changed the
object layout (not just mangling), this makes a lot of sense. I haven't
investigated more than that, I'm afraid.


> To solve this issue, Clang only would have to implement the return type ABI
> tagging. All other ABI tags are irrelevant AFAIK.

If I read correctly, one of the emails says this is only temporary, and
wouldn't show in the final object, since C++ doesn't distinguish return
types, that's most useful.

That seems to imply that we'd need IR representations, in addition to
mangling, and that the back-ends will have to carry it all the way to
assembly (but not object) output, which doesn't seem like a small
change. If this needs to stay until emission, we can't use metadata, it
needs to be a full-fledged IR construct.

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You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[James-molloy-u]

This is a feature, not a bug. Features do not block releases.

It's a feature because it's new behaviour to be added to Clang, not a
regression in an old behaviour. That GCC designed and implemented this
and that Linux distributions took that and ran with it is irritating,
but does not make it a release blocker.

Implementing a new feature is not a one line fix, it's not something
that can be merged to the release branch quickly - it needs design
(especially in this case!) and soak testing.

It's nigh-on impossible for this to be done for the release, and
therefore it makes no sense to have it block the release IMHO.

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Renato Golin]

(In reply to comment #26)
> No. It was implemented in April this year, shortly before the gcc-5 release.
> I've pointed out compatibility issue immediately:
> https://gcc.gnu.org/ml/gcc-patches/2015-04/msg00153.html
(...)
> The were no behavioral changes at all after that patch went in.

In the Linaro thread, Jim points out to the abi_tag patch from 2012.
Your mention is about "significant changes to attribute abi_tag". I
can't see how I was wrong.


> No gcc-5 doesn't default to C++11 and the issue here has nothing to do with 
> C++98 vs. C++11.
> 
> Please try to get the facts strait, before posting long misleading replies.

This is what most of the documentation, email threads and conversations
I had seem to point at. If you have a different opinion, than by all
means, please share your knowledge.

Saying "it has nothing to do with" doesn't explain what it has to do
with. I'm happy to be proven wrong here, as long as we get all the facts
on the table. This bug doesn't seem to provide strong facts either.

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Octoploid]

(In reply to comment #25)
> Following up on the Linaro Toolchain list[1], I found out a few facts:
> 
> 1. This feature was implemented in GCC and libstdc++ in 2012, after
> discussions on the cauldron with distro representatives.

No. It was implemented in April this year, shortly before the gcc-5 release.
I've pointed out compatibility issue immediately:
https://gcc.gnu.org/ml/gcc-patches/2015-04/msg00153.html

> 2. The feature is poorly documented, and may have changed behaviour until
> recently. I have no evidence of changes, is anyone does, please update.

The were no behavioral changes at all after that patch went in.
 
> 3. The problem only started because distros have chosen GCC 5 as their
> default compilers for the current releases, which defaults to C++11.

No gcc-5 doesn't default to C++11 and the issue here has nothing to do with 
C++98 vs. C++11.

Please try to get the facts strait, before posting long misleading
replies.

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254]

[Tim Jones]

-1 for this being considered a feature request.

It's blocking anyone from updating their OSs in our company, which isn't
going to happen, so we'll likely have to switch everything back to g++
only.

I'm sure we're not the only ones.

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Daniel-f-starke]

I admit that adding this new functionality sounds more like a feature request 
than a bug. But as I understood it, LLVM/Clang claims to support GCC and its 
libraries with a minimum version required.
No user would expect there to be an maximum version requirement.
I see two possible ways here for the next release:
1. State that LLVM/Clang only works up to GCC 4.9.
2. Add this attribute to be compatible to the most recent GCC release (5.3) 
again.
For future releases of LLVM/Clang this PR may as well be treated as a feature 
request IMHO.

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Steven Noonan]

I tried the "abi-tag patch version 4" attachment, and it appears to
introduce some compiler crashes under 'make check-all'. Try out
test/CodeGenCXX/static-local-in-local-class.cpp and you appear to get
unbounded recursion:

$ gdb --args /home/steven/Development/llvm/build/Release/bin/clang -cc1 
-internal-isystem 
/home/steven/Development/llvm/build/Release/bin/../lib/clang/3.7.0/include 
-nostdsysteminc -triple x86_64-linux -fblocks -emit-llvm -o - 
/home/steven/Development/llvm/tools/clang/test/CodeGenCXX/static-local-in-local-class.cpp
 -std=c++1y
[...]
(gdb) bt
[...]
#26382 0x014814c3 in (anonymous 
namespace)::CXXNameMangler::mangleLocalName(clang::Decl const*, 
llvm::SmallVector const*, bool) ()
#26383 0x01481ef7 in (anonymous 
namespace)::CXXNameMangler::mangleNameWithAbiTags(clang::NamedDecl const*, 
llvm::SmallVector const*, bool) ()
#26384 0x0147c030 in (anonymous 
namespace)::CXXNameMangler::mangleName(clang::NamedDecl const*, bool) ()
#26385 0x01479308 in (anonymous 
namespace)::CXXNameMangler::mangleType(clang::QualType) ()
#26386 0x0147cb74 in (anonymous 
namespace)::CXXNameMangler::mangleFunctionEncoding(clang::FunctionDecl const*, 
bool) ()
#26387 0x014814c3 in (anonymous 
namespace)::CXXNameMangler::mangleLocalName(clang::Decl const*, 
llvm::SmallVector const*, bool) ()
#26388 0x01481ef7 in (anonymous 
namespace)::CXXNameMangler::mangleNameWithAbiTags(clang::NamedDecl const*, 
llvm::SmallVector const*, bool) ()
#26389 0x0147c030 in (anonymous 
namespace)::CXXNameMangler::mangleName(clang::NamedDecl const*, bool) ()
#26390 0x01479308 in (anonymous 
namespace)::CXXNameMangler::mangleType(clang::QualType) ()
#26391 0x0147cb74 in (anonymous 
namespace)::CXXNameMangler::mangleFunctionEncoding(clang::FunctionDecl const*, 
bool) ()
#26392 0x014814c3 in (anonymous 
namespace)::CXXNameMangler::mangleLocalName(clang::Decl const*, 
llvm::SmallVector const*, bool) ()
#26393 0x01481ef7 in (anonymous 
namespace)::CXXNameMangler::mangleNameWithAbiTags(clang::NamedDecl const*, 
llvm::SmallVector const*, bool) ()
#26394 0x0147c030 in (anonymous 
namespace)::CXXNameMangler::mangleName(clang::NamedDecl const*, bool) ()
#26395 0x01479308 in (anonymous 
namespace)::CXXNameMangler::mangleType(clang::QualType) ()
#26396 0x0147cb74 in (anonymous 
namespace)::CXXNameMangler::mangleFunctionEncoding(clang::FunctionDecl const*, 
bool) ()
#26397 0x01481367 in (anonymous 
namespace)::ItaniumMangleContextImpl::mangleCXXName(clang::NamedDecl const*, 
llvm::raw_ostream&) ()
#26398 0x009e9eae in 
clang::CodeGen::CodeGenModule::getMangledName(clang::GlobalDecl) ()
#26399 0x009eb14a in 
clang::CodeGen::CodeGenModule::GetAddrOfFunction(clang::GlobalDecl, 
llvm::Type*, bool, bool) ()
#26400 0x00abf7c0 in 
clang::CodeGen::CodeGenFunction::EmitCXXMemberOrOperatorMemberCallExpr(clang::CallExpr
 const*, clang::CXXMethodDecl const*, clang::CodeGen::ReturnValueSlot, bool, 
clang::NestedNameSpecifier*, bool, clang::Expr const*) ()
#26401 0x00abfe63 in 
clang::CodeGen::CodeGenFunction::EmitCXXOperatorMemberCallExpr(clang::CXXOperatorCallExpr
 const*, clang::CXXMethodDecl const*, clang::CodeGen::ReturnValueSlot) ()
#26402 0x00ab4d3f in 
clang::CodeGen::CodeGenFunction::EmitCallExpr(clang::CallExpr const*, 
clang::CodeGen::ReturnValueSlot) ()
#26403 0x00ab4f7a in 
clang::CodeGen::CodeGenFunction::EmitCallExprLValue(clang::CallExpr const*) ()
#26404 0x00ab1a56 in 
clang::CodeGen::CodeGenFunction::EmitLValue(clang::Expr const*) ()
#26405 0x00ab1de9 in 
clang::CodeGen::CodeGenFunction::EmitCastLValue(clang::CastExpr const*) ()
#26406 0x00ab1a3e in 
clang::CodeGen::CodeGenFunction::EmitLValue(clang::Expr const*) ()
#26407 0x00abf635 in 
clang::CodeGen::CodeGenFunction::EmitCXXMemberOrOperatorMemberCallExpr(clang::CallExpr
 const*, clang::CXXMethodDecl const*, clang::CodeGen::ReturnValueSlot, bool, 
clang::NestedNameSpecifier*, bool, clang::Expr const*) ()
#26408 0x00abfe63 in 
clang::CodeGen::CodeGenFunction::EmitCXXOperatorMemberCallExpr(clang::CXXOperatorCallExpr
 const*, clang::CXXMethodDecl const*, clang::CodeGen::ReturnValueSlot) ()
#26409 0x00ab4d3f in 
clang::CodeGen::CodeGenFunction::EmitCallExpr(clang::CallExpr const*, 
clang::CodeGen::ReturnValueSlot) ()
#26410 0x006959fa in (anonymous 
namespace)::ScalarExprEmitter::VisitCallExpr(clang::CallExpr const*) ()
#26411 0x00ad7c0c in (anonymous 
namespace)::ScalarExprEmitter::Visit(clang::Expr*) ()
#26412 0x00ad88c0 in 
clang::CodeGen::CodeGenFunction::EmitScalarExpr(clang::Expr const*, bool) ()
#26413 0x009b4f44 in 
clang::CodeGen::CodeGenFunction::EmitReturnStmt(clang::ReturnStmt const&) ()
#26414 

[Desktop-packages] [Bug 1488254]

[Rnk]

*** Bug 25656 has been marked as a duplicate of this bug. ***

-- 
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[İsmail Dönmez]

Any news on this? This is blocking any recent Linux distribution.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Benzejaa]

*** Bug 24844 has been marked as a duplicate of this bug. ***

-- 
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++ in wily

[Daniel van Vugt]

** Summary changed:

- clang++ no longer ABI-compatible with g++
+ clang++ no longer ABI-compatible with g++ in wily

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++ in wily

[Daniel van Vugt]

** Changed in: llvm-toolchain-3.6 (Ubuntu)
   Importance: Undecided => High

** Summary changed:

- clang++ no longer ABI-compatible with g++ in wily
+ clang++ no longer ABI-compatible with g++

-- 
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++ in wily

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: llvm-toolchain-3.6 (Ubuntu)
   Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

Tracking my patch now in http://reviews.llvm.org/D12834

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Richard-llvm]

Please post your patch to cfe-comm...@lists.llvm.org for review; very
few people will see it here.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

Created attachment 14872
abi-tag patch version 3

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

Created attachment 14874
abi-tag patch version 4

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

Created attachment 14873
document abi-tag mangling

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

Created attachment 14868
second attempt to add abi_tag

I came up with a list of various tests and compared the results.. and
worked hard to improve the patch :)

http://files.stbuehler.de/test-itanium-mangle.html shows the test
results (produced with http://files.stbuehler.de/test-itanium-
mangle.sh). Some of the mangling results from gcc could also be
considered completely broken (unnecessary emitted tags, missing tags in
guard variables).

I fear the performance of the patch might be less than optimal though.

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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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[Desktop-packages] [Bug 1488254]

[Lighttpd-2]

Created attachment 14852
first attempt to add abi_tag support

As debian testing now moved to the new gcc abi and I still want to be
able to use clang I tried patching it myself.

Certainly not perfect, and you'll notice some places where I am
uncertain whether abi tags need to be emitted in the name mangling, and
I wasn't able to get the NamedDecl pointer for the emitted identifier.

Patch was created against http://llvm.org/svn/llvm-project/cfe/trunk
246931.

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https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include 
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include 
  #include 
  extern std::string hello;
  int main() {
  std::cout << hello;
  return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254] [NEW] clang++ no longer ABI-compatible with g++

[Anders Kaseorg]

Public bug reported:

$ cat foo.cc
#include string
std::string hello = Hello, world!\n;
$ cat bar.cc
#include string
#include iostream
extern std::string hello;
int main() {
std::cout  hello;
return 0;
}
$ g++ -c foo.cc  g++ foo.o bar.cc  ./a.out
Hello, world!
$ clang++ -c foo.cc  clang++ foo.o bar.cc  ./a.out
Hello, world!
$ g++ -c foo.cc  clang++ foo.o bar.cc  ./a.out
/tmp/bar-34fb23.o: In function `main':
bar.cc:(.text+0x14): undefined reference to `hello'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
$ clang++ -c foo.cc  g++ foo.o bar.cc  ./a.out
/tmp/ccqU38Mh.o: In function `main':
bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
collect2: error: ld returned 1 exit status

In practice, this means that many programs using C++ libraries other
than libstdc++ fail to compile with clang++. For example, mosh fails
with undefined references to google::protobuf::internal::empty_string_,
google::protobuf::MessageLite::InitializationErrorString() const, and
google::protobuf::MessageLite::SerializeAsString() const.

** Affects: llvm
 Importance: Unknown
 Status: Unknown

** Affects: llvm-toolchain-3.6 (Ubuntu)
 Importance: Undecided
 Status: New

** Bug watch added: llvm.org/bugs/ #23529
   http://llvm.org/bugs/show_bug.cgi?id=23529

** Also affects: llvm via
   http://llvm.org/bugs/show_bug.cgi?id=23529
   Importance: Unknown
   Status: Unknown

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You received this bug notification because you are a member of Desktop
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Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Unknown
Status in llvm-toolchain-3.6 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include string
  std::string hello = Hello, world!\n;
  $ cat bar.cc
  #include string
  #include iostream
  extern std::string hello;
  int main() {
  std::cout  hello;
  return 0;
  }
  $ g++ -c foo.cc  g++ foo.o bar.cc  ./a.out
  Hello, world!
  $ clang++ -c foo.cc  clang++ foo.o bar.cc  ./a.out
  Hello, world!
  $ g++ -c foo.cc  clang++ foo.o bar.cc  ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc  g++ foo.o bar.cc  ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

To manage notifications about this bug go to:
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[Desktop-packages] [Bug 1488254] Re: clang++ no longer ABI-compatible with g++

[Bug Watch Updater]

Launchpad has imported 7 comments from the remote bug at
https://llvm.org/bugs/show_bug.cgi?id=23529.

If you reply to an imported comment from within Launchpad, your comment
will be sent to the remote bug automatically. Read more about
Launchpad's inter-bugtracker facilities at
https://help.launchpad.net/InterBugTracking.


On 2015-05-14T21:23:35+00:00 Bero-b wrote:

With the release of gcc 5.1, libstdc++ has started using the abi_tag
attribute.

The attribute is documented here:
https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Attributes.html

Its use in libstdc++ and effects on ABI compatibility between gcc and clang are 
pointed out here:
https://gcc.gnu.org/ml/gcc-patches/2015-04/msg00153.html

It would be great if clang could support the abi_tag attribute and
remain abi compatible with gcc.

Reply at: https://bugs.launchpad.net/ubuntu/+source/llvm-
toolchain-3.6/+bug/1488254/comments/0


On 2015-05-15T11:08:15+00:00 Renato Golin wrote:

If I understand the problem, even old GCCs will have such compatibility
issues.

So, what GCC 5 is leading to, is a system that no other compiler can
coexist without supporting abi_tags. This is bad not just for Clang, but
for anyone experimenting with GCC 5 on a system based on 4.x, or
reverting the compiler to work around 5.0 bugs.

If GCC 5 cannot work alongside compilers that don't support abi_tag,
than maybe the abi_tag implementation needs to be reviewed, and
rewritten so that they do.

Reply at: https://bugs.launchpad.net/ubuntu/+source/llvm-
toolchain-3.6/+bug/1488254/comments/1


On 2015-05-15T11:15:58+00:00 Renato Golin wrote:

I've added a few people to the bug, as this looks like a watershed
moment. I can't grasp the full extent of the problem right now, but I'm
hoping that Clang folks are already aware of the changes in libstdc++
and have a plan. :)

I'd also like to make sure we don't move away from libstdc++ just
because of that. We need to support all mainstream C++ libraries.

Reply at: https://bugs.launchpad.net/ubuntu/+source/llvm-
toolchain-3.6/+bug/1488254/comments/2


On 2015-05-15T20:39:00+00:00 Richard-llvm wrote:

David has started looking into this. Apparently there are many
implementation bugs on the GCC side (in addition to all the other
problems with this attribute), and it's not yet clear how many of them
we'll need to be compatible with.

Reply at: https://bugs.launchpad.net/ubuntu/+source/llvm-
toolchain-3.6/+bug/1488254/comments/3


On 2015-05-15T21:13:03+00:00 Tim Northover wrote:

Isn't this precisely the kind of thing cxx-abi-dev exists to make saner?
(Or would have, if it had been used).

Reply at: https://bugs.launchpad.net/ubuntu/+source/llvm-
toolchain-3.6/+bug/1488254/comments/4


On 2015-06-20T05:32:52+00:00 Zeratul976 wrote:

Is there any update on this? The current ABI incompatibility between the
latest released versions of gcc and clang in their default
configurations is very unfortunate.

Reply at: https://bugs.launchpad.net/ubuntu/+source/llvm-
toolchain-3.6/+bug/1488254/comments/5


On 2015-08-06T23:19:20+00:00 Jristz wrote:

Any news in this issue?
last real comment was from june and that near 3 months ago.

Reply at: https://bugs.launchpad.net/ubuntu/+source/llvm-
toolchain-3.6/+bug/1488254/comments/6


** Changed in: llvm
   Status: Unknown = Confirmed

** Changed in: llvm
   Importance: Unknown = Medium

-- 
You received this bug notification because you are a member of Desktop
Packages, which is subscribed to llvm-toolchain-3.6 in Ubuntu.
https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  New

Bug description:
  $ cat foo.cc
  #include string
  std::string hello = Hello, world!\n;
  $ cat bar.cc
  #include string
  #include iostream
  extern std::string hello;
  int main() {
  std::cout  hello;
  return 0;
  }
  $ g++ -c foo.cc  g++ foo.o bar.cc  ./a.out
  Hello, world!
  $ clang++ -c foo.cc  clang++ foo.o bar.cc  ./a.out
  Hello, world!
  $ g++ -c foo.cc  clang++ foo.o bar.cc  ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
  $ clang++ -c foo.cc  g++ foo.o bar.cc  ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many