The problem is that on some systems, including Tru64 and I believe AIX, the compiler has to be passed the -pthread command line option in order to use #include <pthread.h>
Effectively, the first lines of /usr/include/pthread.h contain the lines: #ifndef _REENTRANT #error POSIX pthreads are only available with the use of -pthreads #endif For this reason the autoconf tests of pthread.h in libstdc++-v3 and libgomp always fail. Fortunately, this was previously not serious, as the target configurations would include pthread.h anyway, and all the relevant source libraries are compiled with -pthread. In directories where they don't, GCC has workarounds, such as in gcc/gcc-posix.h which contains the lines: /* Some implementations of <pthread.h> require this to be defined. */ #ifndef _REENTRANT #define _REENTRANT 1 #endif #include <pthread.h> This issue escalcated to a bootstrap failure in libgomp recently, which now aborts whilst configuring libgomp when pthread.h isn't detected. Prior to this change, libgomp built fine and the test results were quite reasonable on Alpha/Tru64. [Stretching the definition of a regression :-)] I believe that what is needed is a "local" configure test for pthread.h that first decides whether the compiler supports -pthread (for example, GCC on IRIX currently does not), and then uses this flag testing for headers. This is perhaps similar to the related patch I posted recently, where we need to test system header with the same compiler options we'll be using to build the source files: http://gcc.gnu.org/ml/gcc-patches/2006-01/msg00139.html See the related definitions of THREADCXXFLAGS and THREADLDFLAGS in libjava's configure.ac. Unfortunately, my autoconf-fu isn't strong enough to tackle this. The temporary work-around is to use --disable-libgomp. The long-term fix would be to port libgomp to use GCC's gthreads library. But in the meantime, it would be good to correct the test for pthread.h and/or add a PTHREAD_CFLAGS that can be used any project. I'm happy to test patches on affected systems. However, it should be trivial to re-create a model system with the above lines and using -D_REENTRANT as the compiler option that needs to be passed. -- Summary: Configure tests for pthread.h sometimes need to use - pthread Product: gcc Version: 4.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: bootstrap AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: roger at eyesopen dot com GCC host triplet: alpha*-*-osf* http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26161
