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FindThreads: Revert libc symbol check to pthread_create

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Since commit e9a1ddc594 (FindThreads: Replace the pthread symbol
checking in libc., 2018-11-18, v3.14.0-rc1~292^2) we check libc for
`pthread_kill` instead of `pthread_create`.  However, on FreeBSD
`pthread_kill` is in libc but not `pthread_create`.  Discussion in the
original merge request for the above commit also considered
`pthread_key_create`, `pthread_self`, and `pthread_attr_init`.  Every
symbol seems to have some reason it is not an appropriate choice.

Revert to the pre-3.14 behavior of using `pthread_create` pending
further investigation.
This commit is contained in:
Brad King
2019-02-27 07:28:05 -05:00
parent e0267eb1d3
commit 18320230ec
1 changed files with 3 additions and 13 deletions
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16
Modules/FindThreads.cmake
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@@ -118,18 +118,8 @@ if(CMAKE_HAVE_PTHREAD_H)
set(CMAKE_HAVE_THREADS_LIBRARY)
if(NOT THREADS_HAVE_PTHREAD_ARG)
# Check if pthread functions are in normal C library.
# If the pthread functions already exist in C library, we could just use
# them instead of linking to the additional pthread library. We could
# try to check any pthread symbol name, but here is an exception. If we
# use clang asan build, we will find the pthread_create() symbol in the
# libc(libasan). However, it doesn't have the full pthread implementation.
# So, we can't assume that we have the pthread implementation in libc
# using the pthread_create() checking here. Then, we turn to check the
# pthread_kill() symbol instead. It is in the "signal.h" header, but
# the purpose of this check is to verify that the pthread API works with
# pure libc, so verify that "pthread.h" can be included too.
CHECK_SYMBOL_EXISTS(pthread_kill "signal.h;pthread.h" CMAKE_HAVE_LIBC_PTHREAD_KILL)
if(CMAKE_HAVE_LIBC_PTHREAD_KILL)
CHECK_SYMBOL_EXISTS(pthread_create pthread.h CMAKE_HAVE_LIBC_CREATE)
if(CMAKE_HAVE_LIBC_CREATE)
set(CMAKE_THREAD_LIBS_INIT "")
set(CMAKE_HAVE_THREADS_LIBRARY 1)
set(Threads_FOUND TRUE)
@@ -154,7 +144,7 @@ if(CMAKE_HAVE_PTHREAD_H)
_check_pthreads_flag()
endif()
if(CMAKE_THREAD_LIBS_INIT OR CMAKE_HAVE_LIBC_PTHREAD_KILL)
if(CMAKE_THREAD_LIBS_INIT OR CMAKE_HAVE_LIBC_CREATE)
set(CMAKE_USE_PTHREADS_INIT 1)
set(Threads_FOUND TRUE)
endif()