my_pthread.c:

  Backport of correction for Mac OS X build problem, global variable not
  initiated is "common" and can't be used in shared libraries, unless
  special flags are used (bug#26218)

mysys/my_pthread.c

@@ -30,7 +30,7 @@
 #define SCHED_POLICY SCHED_OTHER
 #endif
 
-uint thd_lib_detected;
+uint thd_lib_detected= 0;
 
 #ifndef my_pthread_setprio
 void my_pthread_setprio(pthread_t thread_id,int prior)