Re: Yocto development with C++11 threads and gcc

["Peter A. Bigot" <pab@pabigot.com>]

On 08/11/2014 02:02 PM, Peter A. Bigot wrote:
> The program below built on the target with the MACHINE=beaglebone 
> gcc-4.9.1 compiler from Yocto/OpenEmbedded poky master produces this 
> error:
>
> beaglebone[52]$ g++ -std=c++1y -pthread test.cc && ./a.out
> starting
> joining
> pure virtual method called
> terminate called without an active exception
> Aborted (core dumped)
>
> When the program is recompiled with the defines for 
> __GCC_HAVE_SYNC_COMPARE_AND_SWAP_X enabled as suggested at 
> https://groups.google.com/d/msg/automatak-dnp3/Jisp_zGhd5I/ck_Cj6nO8joJ it 
> works:
>
> beaglebone[53]$ g++ -std=c++1y -pthread test.cc && ./a.out
> starting
> joining
> doit
> done
>
> Preliminary analysis confirms that the built-ins for those defines are 
> not being added by the compiler because it thinks the target doesn't 
> support those operations.  Nonetheless, it doesn't use the substitutes 
> that are obviously available.
>
> Can anybody recall anything about the way GCC is built under OE that 
> would explain this?

Not an OE problem.  See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62100

I'm testing a patch locally and awaiting GCC maintainer comment before 
proposing it for OE.

Peter

>
> Peter
>
> /* g++ -std=c++1y -pthread test.cc && ./a.out */
> #if 0
> #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1
> #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2
> #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
> #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8
> #endif
>
> #include <iostream>
> #include <thread>
>
> void
> doit ()
> {
>   std::cerr << "doit\n";
> }
>
> int main (int argc,
>           char * argv [])
> {
>   std::cerr << "starting\n";
>   std::thread thr{doit};
>   std::cerr << "joining\n";
>   thr.join();
>   std::cerr << "done\n";
>   return 0;
> }
>