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Date: Wed, 29 Apr 2009 10:51:35 +0100
From: Dave Korn <dave DOT korn DOT cygwin AT googlemail DOT com>
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Subject: Re: GCC 4.4.0 - Can't activate threading support
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Dave Korn wrote:
> Casull wrote:
>> The GCC 4.4 implementation of std::thread is guarded by the
>> following preprocessing directive:
>>
>>    #if defined(_GLIBCXX_HAS_GTHREADS) &&
>> defined(_GLIBCXX_USE_C99_STDINT_TR1)
>>
>> When looking at the bits/c++config.h, _GLIBCXX_USE_C99_STDINT_TR1 is defined
>> but _GLIBCXX_HAS_GTHREADS isn't.
> 
>   Ah.  There is an autoconf test in libstdc++-v3 that defines that, and the
> comment says:
> 
>> dnl Check if gthread implementation defines the types and functions
>> dnl required by the c++0x thread library.  Conforming gthread
>> dnl implementations can define __GTHREADS_CXX0X to enable use with c++0x.

  It fails because :

// In case of POSIX threads check _POSIX_TIMEOUTS too.
#if (defined(_PTHREADS) && (!defined(_POSIX_TIMEOUTS) || _POSIX_TIMEOUTS <= 0))
#error
#endif


... we don't have any definition of _POSIX_TIMEOUTS.  That's a feature test
macro the exact definition of which I haven't found yet, but from libstdc's
point of view, it appears to mean that the pthread_mutex_timedlock function is
supported.  Which indeed Cygwin doesn't currently implement.

http://www.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_timedlock.html

  Looks like it wouldn't be too hard to add, PTC I suppose.

    cheers,
      DaveK


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