FindThreads: Replace the pthread symbol checking in libc.

With asan build, we will have the pthread_create() symbol in libc. However,
libasan doesn't have full pthread implementation. We can't assume that we
have the pthread implementation in libc using pthread_create() symbol.
Replace the pthread_create() with pthread_kill() as a quick fix.

1 files changed, 12 insertions, 4 deletions

diff --git a/Modules/FindThreads.cmake b/Modules/FindThreads.cmake
index dfb683f32d..691b1b7e9d 100644
--- a/Modules/FindThreads.cmake
+++ b/Modules/FindThreads.cmake
@@ -131,9 +131,17 @@ else()
     #
     set(CMAKE_HAVE_THREADS_LIBRARY)
     if(NOT THREADS_HAVE_PTHREAD_ARG)
-      # Check if pthread functions are in normal C library
-      CHECK_SYMBOL_EXISTS(pthread_create pthread.h CMAKE_HAVE_LIBC_CREATE)
-      if(CMAKE_HAVE_LIBC_CREATE)
+      # 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.
+      CHECK_SYMBOL_EXISTS(pthread_kill pthread.h CMAKE_HAVE_LIBC_PTHREAD_KILL)
+      if(CMAKE_HAVE_LIBC_PTHREAD_KILL)
         set(CMAKE_THREAD_LIBS_INIT "")
         set(CMAKE_HAVE_THREADS_LIBRARY 1)
         set(Threads_FOUND TRUE)
@@ -159,7 +167,7 @@ else()
   endif()
 endif()
 
-if(CMAKE_THREAD_LIBS_INIT OR CMAKE_HAVE_LIBC_CREATE)
+if(CMAKE_THREAD_LIBS_INIT OR CMAKE_HAVE_LIBC_PTHREAD_KILL)
   set(CMAKE_USE_PTHREADS_INIT 1)
   set(Threads_FOUND TRUE)
 endif()