Use prctl on Linux to follow standard GNU/Linux functions

thpool.c

@@ -8,9 +8,6 @@
  * 
  ********************************/
 
-#if defined(__linux__)
-#define _GNU_SOURCE
-#endif
 #include <unistd.h>
 #include <signal.h>
 #include <stdio.h>
@@ -18,6 +15,9 @@
 #include <pthread.h>
 #include <errno.h>
 #include <time.h> 
+#if defined(__linux__)
+#include <sys/prctl.h>
+#endif
 #include "thpool.h"
 
 #ifdef THPOOL_DEBUG
@@ -306,7 +306,8 @@ static void* thread_do(struct thread* thread_p){
 	sprintf(thread_name, "thread-pool-%d", thread_p->id);
 
 #if defined(__linux__)
-	pthread_setname_np(thread_p->pthread, thread_name);
+	/* Use prctl instead to prevent using _GNU_SOURCE flag and implicit declaration */
+	prctl(PR_SET_NAME, thread_name);
 #elif defined(__APPLE__) && defined(__MACH__)
 	pthread_setname_np(thread_name);
 #else