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

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

On 08/13/2014 04:23 PM, Peter A. Bigot wrote:
> On 08/13/2014 04:18 PM, Khem Raj wrote:
>> On Mon, Aug 11, 2014 at 12:02 PM, Peter A. Bigot <pab@pabigot.com> 
>> 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?
>> Can you add -mcpu=cortex-a8 to your cmdline and see if it solves the 
>> problem ?
>
> Yes, it does.  That's a good clue.

More specifically, the build logs say gcc-runtime was built with:

arm-poky-linux-gnueabi-gcc  -march=armv7-a -mthumb-interwork 
-mfloat-abi=hard -mfpu=neon -mtune=cortex-a8

and using those flags instead of -mcpu=cortex-a8 also solves the problem.

So either gcc-runtime needs to stop using those flags, or gcc itself 
needs to default to them.  Or some other solution.

In any case, Khem can you run with this?  It'd be fixed a lot better 
that way....

Peter

>
> 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;
>>> }
>>>
>>> -- 
>>> _______________________________________________
>>> Openembedded-core mailing list
>>> Openembedded-core@lists.openembedded.org
>>> http://lists.openembedded.org/mailman/listinfo/openembedded-core
>