Fix check for pthreads library on Ubuntu.

CMakeLists.txt

@@ -145,15 +145,25 @@ set (CMAKE_THREAD_PREFER_PTHREAD TRUE)
 find_package (ThreadsCXX)
 if (Threads_FOUND AND CMAKE_USE_PTHREADS_INIT)
   set (GFLAGS_HAVE_PTHREAD TRUE)
-  check_type_size (pthread_rwlock_t GFLAGS_HAVE_RWLOCK LANGUAGE CXX)
+  check_type_size (pthread_rwlock_t RWLOCK LANGUAGE CXX)
+  if (HAVE_RWLOCK)
+    set (GFLAGS_HAVE_RWLOCK TRUE)
+  else ()
+    set (GFLAGS_HAVE_RWLOCK FALSE)
+  endif ()
 else ()
   set (GFLAGS_HAVE_PTHREAD FALSE)
 endif ()
 
 if (UNIX AND NOT GFLAGS_HAVE_PTHREAD AND BUILD_gflags_LIB)
   set_property (CACHE BUILD_gflags_LIB PROPERTY VALUE OFF)
+  if (CMAKE_HAVE_PTHREAD_H)
+    message (WARNING "Could not find the pthread(s) library."
+                     " Disabling the build of the multi-threaded gflags library.")
+  else ()
     message (WARNING "Could not find the <pthread.h> header file."
                      " Disabling the build of the multi-threaded gflags library.")
+  endif ()
 endif ()
 
 # ----------------------------------------------------------------------------

cmake/CheckForPthreads.cxx

+#include <stdio.h>
+#include <pthread.h>
+#include <unistd.h>
+
+void* runner(void*);
+
+int res = 0;
+#ifdef __CLASSIC_C__
+int main(){
+  int ac;
+  char*av[];
+#else
+int main(int ac, char*av[]){
+#endif
+  pthread_t tid[2];
+  pthread_create(&tid[0], 0, runner, (void*)1);
+  pthread_create(&tid[1], 0, runner, (void*)2);
+
+#if defined(__BEOS__) && !defined(__ZETA__) // (no usleep on BeOS 5.)
+  usleep(1); // for strange behavior on single-processor sun
+#endif
+
+  pthread_join(tid[0], 0);
+  pthread_join(tid[1], 0);
+  if(ac > 1000){return *av[0];}
+  return res;
+}
+
+void* runner(void* args)
+{
+  int cc;
+  for ( cc = 0; cc < 10; cc ++ )
+    {
+    printf("%p CC: %d\n", args, cc);
+    }
+  res ++;
+  return 0;
+}

cmake/FindThreadsCXX.cmake

@@ -38,6 +38,7 @@ include (CheckCXXLibraryExists)
 include (CheckCXXSymbolExists)
 set(Threads_FOUND FALSE)
 
+
 # Do we have sproc?
 if(CMAKE_SYSTEM MATCHES IRIX AND NOT CMAKE_THREAD_PREFER_PTHREAD)
   CHECK_INCLUDE_FILES_CXX("sys/types.h;sys/prctl.h"  CMAKE_HAVE_SPROC_H)
@@ -95,14 +96,15 @@ else()
     endif()
 
     if(NOT CMAKE_HAVE_THREADS_LIBRARY)
-      # If we did not found -lpthread, -lpthread, or -lthread, look for -pthread
+      # If we did not found -lpthread, -lpthreads, or -lthread, look for -pthread
       if("THREADS_HAVE_PTHREAD_ARG" MATCHES "^THREADS_HAVE_PTHREAD_ARG")
         message(STATUS "Check if compiler accepts -pthread")
-        configure_file ("${CMAKE_ROOT}/Modules/CheckForPthreads.c" "${CMAKE_BINARY_DIR}/CheckForPthreads.cxx" COPYONLY)
+        configure_file ("${CMAKE_CURRENT_LIST_DIR}/CheckForPthreads.cxx"
+                        "${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CheckForPthreads.cxx" COPYONLY)
         try_run(THREADS_PTHREAD_ARG THREADS_HAVE_PTHREAD_ARG
           ${CMAKE_BINARY_DIR}
-          ${CMAKE_BINARY_DIR}/CheckForPthreads.cxx
-          CMAKE_FLAGS -DLINK_LIBRARIES:STRING=-pthread
+          ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CheckForPthreads.cxx
+          CMAKE_FLAGS "-DLINK_LIBRARIES:STRING=-pthread;-DCMAKE_CXX_FLAGS:STRING=-fpermissive"
           COMPILE_OUTPUT_VARIABLE OUTPUT)
 
         if(THREADS_HAVE_PTHREAD_ARG)