[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

Andrew Pinski  changed:

   What|Removed |Added

 CC||andrewm.roberts at sky dot com

--- Comment #7 from Andrew Pinski  ---
*** Bug 70211 has been marked as a duplicate of this bug. ***

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[andrewm.roberts at sky dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #8 from Andrew Roberts  ---
The initial bug report was for cross compiling. Bug 70211 is for native builds
on ARM. Given the huge growth in ARM development boards, this needs at least
documenting. As with the original reporter I spent ages trying to figure this
out before stumbling across a solution (and the solution isn't to build GMP out
of tree either). Building GMP out of tree creates another can of worms (esp on
multiarch machines). 

Any documentation fix should mention the targets that need the change (ARM),
and that both cross and native builds are affected. Also reference the
undefined symbol __gmpn_invert_limb so people know they have run across it.

Once you do the above it sort of becomes obvious that actually building GMP
intree with the correct CPU instead of none is proper solution. Or does that
not work for cross compilies? 

The easier it is for people to build gcc themselves the more testing prelease
versions will get.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #9 from Bernd Edlinger  ---
(In reply to Andrew Roberts from comment #8)
> The initial bug report was for cross compiling. Bug 70211 is for native
> builds on ARM. Given the huge growth in ARM development boards, this needs
> at least documenting. As with the original reporter I spent ages trying to
> figure this out before stumbling across a solution (and the solution isn't
> to build GMP out of tree either). Building GMP out of tree creates another
> can of worms (esp on multiarch machines). 
> 
> Any documentation fix should mention the targets that need the change (ARM),
> and that both cross and native builds are affected. Also reference the
> undefined symbol __gmpn_invert_limb so people know they have run across it.
> 
> Once you do the above it sort of becomes obvious that actually building GMP
> intree with the correct CPU instead of none is proper solution. Or does that
> not work for cross compilies? 
> 
> The easier it is for people to build gcc themselves the more testing
> prelease versions will get.

what happens if you use the versions from download_prerequisites?

gmp -> ../gmp-4.3.2
mpc -> ../mpc-0.8.1
mpfr -> ../mpfr-2.4.2

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bneumeier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #10 from Brett Neumeier  ---
Bernd, I don't think there is any argument that those specific versions of the
library dependencies work.

My sense is that it is a bug to assert "GNU Multiple Precision Library (GMP)
version 4.3.2 (or later)" as a prerequisite to GCC on
https://gcc.gnu.org/install/prerequisites.html if versions of GMP later than
4.3.2 do not work in some circumstances.

If it is OK that GCC builds will fail on one or more supported architectures
when using stable released versions of GMP later than 4.3.2, then the
documentation should assert "GMP version 4.3.2" as the prerequisite.

If it is not OK that GCC builds will fail in those circumstances, then the
build machinery for GCC should be fixed.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[andrewm.roberts at sky dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #11 from Andrew Roberts  ---
On Native ARM platform the bootstrap does work with the old in tree GMP 4.3.2,
regardless of wether you use none-linux-gnu or armv7l-linux-gnu when
configuring GMP.

Bulding by patching toplevel Makefile to remove none- and replace with armv7l-
../gcc-6.0.0/configure ...
uname_m=`uname -m`
sed -i "s/none-/${uname_m}-/" Makefile
make
make install

Using:
gmp -> ../gmp-4.3.2
mpc -> ../mpc-0.8.1
mpfr -> ../mpfr-2.4.2 (plus latest patches to mpfr to 2.4.2)
isl -> ../isl-0.16.1

^ Builds Ok and compiles simple program (not bootstrapped due to time taken)

Using:
gmp -> ../gmp-4.3.2
mpc -> ../mpc-0.8.1
mpfr -> ../mpfr-2.4.2 (plus latest patches to mpfr 2.4.2)
isl -> ../isl-0.15 (download_prerequisites version)

^ Builds Ok and compiles simple program (not bootstrapped due to time taken)


Bulding by WITHOUT patching toplevel Makefile but with bootstrapping
../gcc-6.0.0/configure ... --enable-bootstrap
make bootstrap-lean
make install

Using:
gmp -> ../gmp-4.3.2
mpc -> ../mpc-0.8.1
mpfr -> ../mpfr-2.4.2 (plus latest patches to mpfr 2.4.2)
isl -> ../isl-0.15 (download_prerequisites version)

^ Builds and bootstraps Ok and compiles simple program

This is all as expected. But as noted the docs suggest later versions of GMP
are ok as well.

If the build was fixed to use correct CPU for configuring GMP it would build
with both old and new versions of GMP. If there are some specific tests which
would exercise the GMP/ISL parts of gcc I could give them a go as well, but
running the entire test suite would take forever due to the slow storage.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #12 from Bernd Edlinger  ---
It is on purpose that the in-tree gmp is configured to use no assembly,
but the in-tree configuration does not really work with gmp-6.1.0,
and apparently disables the assembly only half-way.  It is not possible
to fix that without breaking compatibility to gmp-4.3.2 at the same time.

I fully agree that it is time to move to a new gmp version for gcc-7,
but if we do so we will also require a specific mpfr and mpc version
too.  And from the experience in the past, I would bet that you
will not be able to simply use any future gmp version,
without very careful testing, and updating mpfr and mpc to compatible
versions at the same time.

As a matter of fact, even when not building in-tree, there are often
incompatibilities:

For instance mpfr-2.4.2/INSTALL says:
0. You first need to install GMP. See .
   MPFR requires GMP version 4.1 or later.

And gmp-6.1.0/INSTALL does not mention MPFR at all.
But building mpfr-2.4.2 with gmp-6.1.0 fails.

For instance mpc-0.8.1/INSTALL says:
0. You first need to install GMP and MPFR. See 
   and .
   MPC requires GMP version 4.2 or later and MPFR version 2.3.1 or later.

And again mpfr-3.1.3/INSTALL does not mention MPC at all.
But building mpc-0.8.1 with gmp-6.1.0 and mpfr-3.1.3 fails.

So it is simply impossible to give any guarantees of that kind.
All we can do is update to a specific gmp/mpfr/mpc version,
and guarantee that exactly that combination will actually work.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bneumeier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #13 from Brett Neumeier  ---
OK, then it would make sense to have a documentation fix for GCC that specifies
those exact versions for GMP, MPC, and MPFR as the versions that must be used,
rather than claiming -- inaccurately! -- "x.y.z or later".

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #14 from Marc Glisse  ---
Note that I don't think we ever got a proper bug report for GMP. Verified
instructions on how to reproduce the issue with just the latest version of GMP
(without having to download the sources of mpfr, mpc, isl, gcc, etc) would be
nice...

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[andrewm.roberts at sky dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #15 from Andrew Roberts  ---
Marc,

not entirely clear what you mean by reproducing the issue without downloading
mpfr, mpc, isl etc. Do you mean the missing symbol in GMP or the issues with
GMP when using assembly code? If you could please clarify.

I've built GMP 6.1.0 on its own on ARM armv7l, using the following
conifgurations:

../gmp-6.1.0/configure --prefix=/home/alarm/gcc/gmp/gmp-default
# This picks armv7lneon as cpu
make
make check
# No Failures
make install
nm ../gmp-default/lib/libgmp.so | grep gmpn_invert_limb
# 0004cca8 T __gmpn_invert_limb

../gmp-6.1.0/configure --prefix=/home/alarm/gcc/gmp/gmp-armv7l \
   --target=armv7l-linux-gnu \
   --build=armv7l-linux-gnu \
   --host=armv7l-linux-gnu
make
make check
# No Failures
make install
nm ../gmp-armv7l/lib/libgmp.so | grep gmpn_invert_limb
# 0004cca8 T __gmpn_invert_limb

../gmp-6.1.0/configure --prefix=/home/alarm/gcc/gmp/gmp-none \
--target=none-linux-gnu \
--build=none-linux-gnu \
--host=none-linux-gnu
make
make check
# No Failures
make install
nm ../gmp-none/lib/libgmp.a | grep gmpn_invert_limb
# no .so built, gmpn_invert_limb not in .a file


I note that GMP 6.1.0 at least as a configure option --enable-assembly=no
which seems to disable the assembly. But as with the none-linux-gnu
configuration this results in no gmpn_invert_limb symbol

../gmp-6.1.0/configure --prefix=/home/alarm/gcc/gmp/gmp-armv7l-noasm \
   --target=armv7l-linux-gnu \
   --build=armv7l-linux-gnu \
   --host=armv7l-linux-gnu \
   --enable-assembly=no
make
make check
# No Failures
make install
nm ../gmp-armv7l-noasm/lib/libgmp.so | grep gmpn_invert_limb
# gmpn_invert_limb not in .so or .a file

So I think the problem is that ISL is using a symbol which isn't always
available on all targets when no assembler is selected. But there might be
merrit investigating the --enable-assembly=no configure flag and which GMP
versions support it.

All of this does raise several isues:
1) If we are trying to disable assembler in GMP for some reason, shouldn't we
tell people building GMP outside of the tree to configure it that way. It seems
strange to have spent time and effort adding all those configuration switches
to find GMP, MPFR, ISL, MPC etc but then saying you really need to build it in
a special way, but we're not documenting it...

2) I've also found that different gcc versions require different versions of
ISL to build. For example ISL 0.14 does not work with gcc < 5.0.0, you need ISL
0.12.2. If there are dependencies on on which versions gcc needs for a given
release, shouldn't they also be documented (and the download_prerequisites
script updated accordingly).

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #16 from Bernd Edlinger  ---
you should use whatever gmp,mpfr,mpc version you like.
with or without assembly should not make any difference.

That should work, but dont expect it to work in-tree.
Instead use the --with-gmp --with-mpfr and --with-mpc
configure options.

Or use the versions that download_prerequisites downloads by default
in-tree, that will work also.

Right?

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #17 from Marc Glisse  ---
(In reply to Andrew Roberts from comment #15)
> not entirely clear what you mean by reproducing the issue without
> downloading mpfr, mpc, isl etc. Do you mean the missing symbol in GMP or the
> issues with GMP when using assembly code? If you could please clarify.

The missing symbol (not sure what "issues with GMP when using assembly code"
you are talking about).

> I've built GMP 6.1.0 on its own on ARM armv7l, using the following
> conifgurations:

The whole point is that those external builds don't seem to reproduce the
issue, probably because they don't use exactly the same options...

> So I think the problem is that ISL is using a symbol which isn't always
> available on all targets when no assembler is selected.

In PR 70211, I see:

/home/alarm/gcc/gcc-build/./gmp/.libs/libgmp.a(divrem_1.o): In function
`__gmpn_divrem_1':
divrem_1.c:(.text+0xb0): undefined reference to `__gmpn_invert_limb'

meaning that the reference to __gmpn_invert_limb comes from GMP itself, not
ISL. If you called nm on this libgmp.a, you would see uses of
__gmpn_invert_limb but no definition.

> 2) I've also found that different gcc versions require different versions of
> ISL to build. For example ISL 0.14 does not work with gcc < 5.0.0, you need
> ISL 0.12.2. If there are dependencies on on which versions gcc needs for a
> given release, shouldn't they also be documented (and the
> download_prerequisites script updated accordingly).

I think download_prerequisites is updated. And the requirements were
documented, although I am not sure how to get them except looking at the
archives for https://gcc.gnu.org/install/prerequisites.html around the date of
the release of 4.9.0 or 5.0.1.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #18 from Marc Glisse  ---
Ah, I managed to reproduce. GMP has a nice "CFLAGS= -g -DNO_ASM" in its
Makefile, but gcc overrides it by calling make CFLAGS=-g. Not much we can do
from the GMP side (and ISL is innocent). Well, maybe the definition of NO_ASM
could move to config.h, but I don't think gcc should be doing what it is doing.

I think this issue was already described in another PR.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #19 from Marc Glisse  ---
(In reply to Marc Glisse from comment #18)
> I think this issue was already described in another PR.

Ah, that was PR 69134 for MPFR.
https://gcc.gnu.org/ml/gcc-patches/2016-01/msg00127.html

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #20 from Marc Glisse  ---
Does the latest GMP snapshot from https://gmplib.org/download/snapshot/ work
for you? I moved NO_ASM to config.h, so GCC's approach of overriding CFLAGS
should not break it anymore.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[andrewm.roberts at sky dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #21 from Andrew Roberts  ---
Tested with:
gcc-6-20160313
and in-tree:
gmp-6.1.99-20160321
mpc-1.0.3
mpfr-3.1.4
isl-0.16.1

On:
x86_64 Centos 7 (Full bootstrap)
This is Ok.

/usr/local/gcc-6.0.0/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/usr/local/gcc-6.0.0/bin/gcc
COLLECT_LTO_WRAPPER=/usr/local/gcc-6.0.0/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-6.0.0/configure --prefix=/usr/local/gcc-6.0.0
--program-suffix= --disable-werror --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-linker-build-id --with-linker-hash-style=gnu --enable-plugin
--enable-initfini-array --enable-gnu-indirect-function --enable-lto --with-isl
--enable-languages=c,c++,fortran --disable-libgcj --with-tune=generic
--enable-multilib --with-arch_32=i686 --host=x86_64-unknown-linux-gnu
--build=x86_64-unknown-linux-gnu --with-ld=/usr/local/bin/ld --with-gnu-ld
--with-as=/usr/local/bin/as --with-gnu-as --enable-bootstrap
Thread model: posix
gcc version 6.0.0 20160313 (experimental) (GCC)
/usr/local/bin/ld -v
GNU ld (GNU Binutils) 2.26.20160125


aarch64  Arch Linux Arm (ODroid-C2) (not stable enough to bootstrap)
This is Ok.

/usr/local/gcc-6.0.0/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/usr/local/gcc-6.0.0/bin/gcc
COLLECT_LTO_WRAPPER=/usr/local/gcc-6.0.0/libexec/gcc/aarch64-unknown-linux-gnu/6.0.0/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: ../gcc-6.0.0/configure --prefix=/usr/local/gcc-6.0.0
--program-suffix= --disable-werror --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-linker-build-id --with-linker-hash-style=gnu --enable-plugin
--enable-initfini-array --enable-gnu-indirect-function --enable-lto --with-isl
--enable-languages=c,c++,fortran --disable-libgcj --enable-clocale=gnu
--disable-libstdcxx-pch --enable-install-libiberty --disable-multilib
--enable-shared --enable-clocale=gnu --with-arch-directory=aarch64
--enable-multiarch --host=aarch64-unknown-linux-gnu
--build=aarch64-unknown-linux-gnu --with-arch=armv8-a --disable-bootstrap
Thread model: posix
gcc version 6.0.0 20160313 (experimental) (GCC)


armv7l Arch Linux Arm (Raspberry Pi 3) (not bootstrapped yet due to build time)

I've not got this working yet, not sure if the new GMP is the issue or changes
in my build scripts. I'll go back to released GMP 6.1 and my working script and
then post the results later today or early tomorrow.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[andrewm.roberts at sky dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #22 from Andrew Roberts  ---
Tested with:
gcc-6-20160313
and in-tree:
gmp-6.1.99-20160321
mpc-1.0.3
mpfr-3.1.4
isl-0.16.1

On:
armv7l Arch Linux Arm (Raspberry Pi 3) (not bootstrapped yet due to build time)
This also builds ok with new GMP snapshot.

/usr/local/gcc-6.0.0/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/usr/local/gcc-6.0.0/bin/gcc
COLLECT_LTO_WRAPPER=/usr/local/gcc-6.0.0/libexec/gcc/armv7l-unknown-linux-gnueab
ihf/6.0.0/lto-wrapper
Target: armv7l-unknown-linux-gnueabihf
Configured with: ../gcc-6.0.0/configure --prefix=/usr/local/gcc-6.0.0
--program-
suffix= --enable-languages=c,c++,fortran --enable-shared --enable-threads=posix 
--with-system-zlib --with-isl --enable-__cxa_atexit
--disable-libunwind-exceptio
ns --enable-clocale=gnu --disable-libstdcxx-pch --disable-libssp
--enable-gnu-un
ique-object --enable-linker-build-id --enable-lto --enable-plugin
--enable-insta
ll-libiberty --with-linker-hash-style=gnu --enable-gnu-indirect-function
--disab
le-multilib --disable-werror --enable-checking=release
--host=armv7l-unknown-lin
ux-gnueabihf --build=armv7l-unknown-linux-gnueabihf
--target=armv7l-unknown-linu
x-gnueabihf --with-arch=armv7-a --with-float=hard --with-fpu=vfpv3-d16
--disable
-bootstrap
Thread model: posix
gcc version 6.0.0 20160313 (experimental) (GCC)

ld -v
GNU ld (GNU Binutils) 2.26.0.20160302

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #23 from Bernd Edlinger  ---
Hi,

I tried this combination in-tree:

gmp -> gmp-6.1.0
mpfr -> mpfr-3.1.3
mpc -> mpc-1.0.3
isl -> isl-1.15

While I can now reproduce the original problem,
I noticed another anomaly:
make check-mpc fails because it does not resolve -lmpfr

make check-mpc
[...]
libtool: link: ( cd ".libs" && rm -f "libmpc-tests.la" && ln -s
"../libmpc-tests.la" "libmpc-tests.la" )
gcc -DHAVE_CONFIG_H -I. -I../../../gcc-trunk/mpc/tests -I.. 
-I../../../gcc-trunk/mpc/src -I/home/ed/gnu/gcc-build/./gmp
-I/home/ed/gnu/gcc-trunk/mpfr/src   -g -O2 -MT tabs.o -MD -MP -MF
.deps/tabs.Tpo -c -o tabs.o ../../../gcc-trunk/mpc/tests/tabs.c
mv -f .deps/tabs.Tpo .deps/tabs.Po
/bin/bash ../libtool  --tag=CC   --mode=link gcc  -g -O2 -no-install
-static-libstdc++ -static-libgcc  -o tabs tabs.o libmpc-tests.la
../src/libmpc.la -lmpfr -lgmp -lm 
libtool: link: gcc -g -O2 -static-libstdc++ -static-libgcc -o tabs tabs.o 
./.libs/libmpc-tests.a ../src/.libs/libmpc.a -lmpfr
/home/ed/gnu/gcc-build/./gmp/.libs/libgmp.a -lm
/usr/bin/ld: cannot find -lmpfr
collect2: error: ld returned 1 exit status
make[3]: *** [tabs] Error 1
make[3]: Leaving directory `/home/ed/gnu/gcc-build/mpc/tests'
make[2]: *** [check-am] Error 2
make[2]: Leaving directory `/home/ed/gnu/gcc-build/mpc/tests'
make[1]: *** [check-recursive] Error 1
make[1]: Leaving directory `/home/ed/gnu/gcc-build/mpc'
make: *** [check-mpc] Error 2

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #24 from Bernd Edlinger  ---
Created attachment 38101
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38101&action=edit
possible patch

Hi,

this is a patch that fixes the check-mpc issue and
fixes gmp-6.1.0 in-tree

The reason for the mpc check problem is that mpfr
changed the place where the libmpfr.la is around.

It was moved from mpfr/.lib to mpfr/src/.lib
and of course, we override LDFLAGS with "-static-libstdc++ -static-libgcc"
while mpc would normally use LDFLAGS="-L.../gcc-build/./gmp/.libs
-L.../gcc-build/./mpfr/.libs -static-libstdc++ -static-libgcc"

That used to work because we also add mpfr/.libs to the
LD_LIBRARY_PATH but we have foggot to ad mpfr/src/.lib
which my patch does, to fix the check-mpc make target.


Bernd.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[andrewm.roberts at sky dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #25 from Andrew Roberts  ---
The patch works on native armv7l-unknown-linux-gnuabihf with:
gcc-6-20160320
and in tree
gmp 6.1.0
mpc 1.0.3
mpfr 3.1.4
isl 0.16.1

although I wasn't seeing a problem with check-mpc.
At least the build completes without needing the GMP snapshot or seding 
none- to `uname -m`- in the makefile.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #26 from Bernd Edlinger  ---
with unpatched trunk and mpfr-3.1.4 and mpc-1.0.3 in-tree

I've got this in mpc/src/libmpc.la:
dependency_libs=' -lmpfr /home/ed/gnu/gcc-build1/./gmp/.libs/libgmp.la -lm'

and check-mpc fails to build this:
libtool: link: /home/ed/gnu/gcc-build1/./prev-gcc/xgcc
-B/home/ed/gnu/gcc-build1/./prev-gcc/
-B/home/ed/gnu/install1/x86_64-pc-linux-gnu/bin/
-B/home/ed/gnu/install1/x86_64-pc-linux-gnu/bin/
-B/home/ed/gnu/install1/x86_64-pc-linux-gnu/lib/ -isystem
/home/ed/gnu/install1/x86_64-pc-linux-gnu/include -isystem
/home/ed/gnu/install1/x86_64-pc-linux-gnu/sys-include -g -O2 -static-libstdc++
-static-libgcc -o tabs tabs.o  ./.libs/libmpc-tests.a ../src/.libs/libmpc.a
-lmpfr /home/ed/gnu/gcc-build1/./gmp/.libs/libgmp.a -lm
/usr/bin/ld: cannot find -lmpfr

and with the patch this line in mpc/src/libmpc.la changed to:
dependency_libs=' /home/ed/gnu/gcc-build/./mpfr/.libs/libmpfr.la
/home/ed/gnu/gcc-build/./gmp/.libs/libgmp.la'

and the check-mpc succeeds on a plain x86_64-ubuntu14.04 with definitely no
gmp or mpfr libs installed

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[edlinger at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

Bernd Edlinger  changed:

   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 Resolution|--- |WONTFIX

--- Comment #27 from Bernd Edlinger  ---
Unfortunately this patch was dismissed, see:

https://gcc.gnu.org/ml/gcc-patches/2016-03/msg01502.html

We will update the download_prerequisite for gcc-7 to
use the "latest" available versions, that is generally
agreed upon.

Therefore I have to set this bug to wont-fix.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

Andrew Pinski  changed:

   What|Removed |Added

  Component|c   |bootstrap
Summary|Build fails when|Build fails when
   |cross-compiling with|cross-compiling with
   |in-tree GMP |in-tree GMP and ISL

--- Comment #1 from Andrew Pinski  ---
Sounds like the bug is an issue with ISL rather than GMP itself.  I don't
normally building with ISL so I have never noticed the issue.

Also I think your patch is incorrect since there is a reason why we disable the
assembly version is because GMP nativelly tries to detect the current processor
and then use the assembler version for that.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bneumeier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #2 from Brett Neumeier  ---
Thanks for your swift comment!

I disagree that the bug is in ISL.  The problem is that gmp, although the build
appears successful, is *not* correctly built.  Six object files that should be
compiled and linked into gmplib.a are not built because they are only built
correctly when assembly is enabled. One of those is invert_limb.o, which
contains the symbol __gmpn_invert_limb, which is needed by ISL.

So the *bug* is in the GMP build, but the *consequence* of the bug is that ISL
cannot be linked.

I agree that my patch is not adequate, though -- I just tested and found that I
couldn't build an x86_64-to-arm cross-gcc when my patch is installed. The
configure for GMP crashes with:

configure: error: --target is not appropriate for GMP
Use --build=CPU-VENDOR-OS if you need to specify your CPU and/or system
explicitly.  Use --host if cross-compiling (see "Installing GMP" in the
manual for more on this).

Obviously the best way to address this situation is by getting GMP to build
properly for all architectures regardless of whether assembly is enabled. Until
or unless that's done, though, it seems like it would be worthwhile to do
*something* to address the issue on the GCC side, since that's where I (and
others, according to google) have tripped over it. Maybe a documentation
change, to say that GMP shouldn't be built in-tree when cross-compiling GCC? Or
something of that sort?

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #3 from Richard Biener  ---
Is __gmpn_invert_limb supposed to be exported?  Or is ISL using private APIs
here?

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

Bernd Edlinger  changed:

   What|Removed |Added

 CC||bernd.edlinger at hotmail dot 
de

--- Comment #4 from Bernd Edlinger  ---
at least this configuration works when doing cross-builds from X86_64 => ARM:


gmp -> ../gmp-4.3.2
mpc -> ../mpc-0.8.1
mpfr -> ../mpfr-2.4.2
isl -> ../isl-0.12.2

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #5 from joseph at codesourcery dot com  ---
GMP does, or did, select an ABI at configuration time that may not be the 
same as that used by default by the compiler used to build it.  For 
example, if building on an x86_64 processor it might select a 64-bit ABI 
even if you have configured GCC for a 32-bit host.  If your goal is to 
make multiple-precision computations as fast as possible, choosing the ABI 
for that purpose makes sense - but for GCC's uses the requirement is to 
choose the same ABI as for the selected host, even if that's slower than 
some other ABI available on the processor.

[Bug bootstrap/67728] Build fails when cross-compiling with in-tree GMP and ISL

[bneumeier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67728

--- Comment #6 from Brett Neumeier  ---
Created attachment 36441
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36441&action=edit
document symptoms of problem and workaround

Since the issue is a corner-case (it's only triggered when cross-compiling for
certain architectures, using recent versions of GMP, and with in-tree GMP and
ISL sources), and since there's an easy and obvious workaround, it seems
pointless to spend a lot of time trying to adjust the build machinery.

On the other hand, a something search reveals I'm not the only person to run
into this situation, so it seems worthwhile to at least document the
workaround. Here's a suggested paragraph -- it would have saved *me* a headache
and a few hours of frustration when I tripped across the problem, so perhaps it
will be helpful to someone else in the future?