On Thu, Nov 16, 2023 at 7:07 PM Bruno Haible <br...@clisp.org> wrote:
> David Edelsohn wrote: > > > ibm-clang links against libpthread.a as well: > > > $ ldd /opt/IBM/openxlC/17.1.1/bin/.ibm-clang.orig > > > /opt/IBM/openxlC/17.1.1/bin/.ibm-clang.orig needs: > > > /usr/lib/libpthreads.a(shr_xpg5_64.o) > > > /usr/opt/zlibNX/lib/libz.a(libz.so.1) > > > /usr/lib/libcurses.a(shr42_64.o) > > > /usr/lib/libiconv.a(shr4_64.o) > > > /usr/lib/libc++.a(shr_64.o) > > > /usr/lib/libc++abi.a(libc++abi.so.1) > > > /usr/lib/libc.a(shr_64.o) > > > /usr/lib/libpthreads.a(_shr_xpg5_64.o) > > > /usr/lib/libc++.a(libc++.so.1) > > > /usr/lib/libunwind.a(libunwind.so.1) > > > /usr/lib/libc.a(_shr_64.o) > > > /unix > > > /usr/lib/libcrypt.a(shr_64.o) > > > > > > > I have asked the IBM Clang team why ibm-clang depends on libpthreads. > > The reason is that > - For a library, it is a normal expectation nowadays that it is > multithread-safe. > - Making a library multithread-safe (without major hacks) means to do > locking or to call pthread_once / call_once in some places. > - The ISO C 11 threading functions in libc have some drawbacks compared > to the pthread functions. [1] So most developer prefer to rely on the > POSIX threads API. > - Since AIX does not have the POSIX mutex functions in libc and does not > support weak symbols like in ELF, this means a dependency to > pthread_mutex_lock or pthread_once. > - Accordingly, in the list of libraries above, 3 libraries need pthread* > symbols: > > $ nm -X 64 /usr/lib/libc++abi.a | grep ' U ' | grep pthread_mutex > pthread_mutex_lock U - > pthread_mutex_unlock U - > $ nm -X 64 /usr/lib/libc++.a | grep ' U ' | grep pthread_mutex > pthread_mutex_destroy U - > pthread_mutex_init U - > pthread_mutex_lock U - > pthread_mutex_trylock U - > pthread_mutex_unlock U - > pthread_mutexattr_destroy U - > pthread_mutexattr_init U - > pthread_mutexattr_settype U - > $ nm -X 64 /usr/opt/zlibNX/lib/libz.a | grep ' U ' | grep pthread_mutex > pthread_mutex_destroy U - > pthread_mutex_init U - > pthread_mutex_lock U - > pthread_mutex_unlock U - > There are ibm_clang and ibm_clang_r (previous xlc and xlc_r) to compile with and without thread safe. If IBM Clang team chose to only provide a thread safe version of libc++, okay, but that doesn't seem like a fundamental requirement. zlibNX is another can of worms. David
