Re: thread_local broken in gcc 4.8 ?

[Conrad S]

On Mon, Jan 6, 2014 at 6:25 PM, Jakub Jelinek  wrote:
> Wonder if the ctor is really trivial it wouldn't be better to treat it as
> not needing dynamic initialization, rather than trying to initialize it
> dynamically.

This is actually a reduced case scenario.
In the original case the constructor is not trivial.

> So, please file this into bugzilla.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59364

Re: thread_local broken in gcc 4.8 ?

[Jakub Jelinek]

On Mon, Jan 06, 2014 at 03:53:13PM +1000, Conrad S wrote:
> According to http://gcc.gnu.org/gcc-4.8/cxx0x_status.html
> the keyword "thread_local" is supported in gcc 4.8 when using -std=c++11

Bugs should be reported to http://gcc.gnu.org/bugzilla/

> file foo.hpp:
> class foo {
>   public:
>   inline  foo() {}
>   inline ~foo() {}
>   inline double bar() { return 123.456; }
>   };
> 
> 
> file a.cpp:
> #include "foo.hpp"
> thread_local foo foo_instance;
> 
> 
> file b.cpp:
> #include "foo.hpp"
> extern thread_local foo foo_instance;
> 
> int main(int argc, char** argv) {
>   double bar = foo_instance.bar();
>   return 0;
>   }

Apparently this got fixed/made latent on the trunk by
http://gcc.gnu.org/r199577 , but it isn't clear if that was an intentional
bugfix somewhere; in any case the patch doesn't look to be backportable.

Wonder if the ctor is really trivial it wouldn't be better to treat it as
not needing dynamic initialization, rather than trying to initialize it
dynamically.

So, please file this into bugzilla.

Jakub

thread_local broken in gcc 4.8 ?

[Conrad S]

According to http://gcc.gnu.org/gcc-4.8/cxx0x_status.html
the keyword "thread_local" is supported in gcc 4.8 when using -std=c++11

However, thread_local seems broken.  Let's say we compile a multi-file
program that uses thread_local:
g++ a.cpp -c -o a.o -std=c++11
g++ b.cpp -c -o b.o -std=c++11
g++ a.o b.o -o prog -std=c++11

We get the following error:
b.o: In function `TLS wrapper function for foo_instance':
b.cpp:(.text._ZTW12foo_instance[_ZTW12foo_instance]+0x5): undefined
reference to `TLS init function for foo_instance'
collect2: error: ld returned 1 exit status

gcc --version
gcc (GCC) 4.8.2 20131212 (Red Hat 4.8.2-7)


file foo.hpp:
class foo {
  public:
  inline  foo() {}
  inline ~foo() {}
  inline double bar() { return 123.456; }
  };


file a.cpp:
#include "foo.hpp"
thread_local foo foo_instance;


file b.cpp:
#include "foo.hpp"
extern thread_local foo foo_instance;

int main(int argc, char** argv) {
  double bar = foo_instance.bar();
  return 0;
  }