In one of the the first threads we launch, test that errno is thread local

and working, and panic with a somewhat usable message if not.

PS: And boy, are you screwed if my test sneaks though a kernel bug...



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4569 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_pool.c

@@ -404,9 +404,21 @@ wrk_herdtimer_thread(void *priv)
 	volatile unsigned u;
 	double t_idle;
 	struct varnish_stats vsm, *vs;
+	int errno_is_multi_threaded;
 
 	THR_SetName("wrk_herdtimer");
 
+	/*
+	 * This is one of the first threads created, test to see that
+	 * errno is really per thread.  If this fails, your C-compiler
+	 * needs some magic argument (-mt, -pthread, -pthreads etc etc).
+	 */
+	errno = 0;
+	AN(unlink("/"));		/* This had better fail */
+	errno_is_multi_threaded = errno;
+	assert(errno_is_multi_threaded != 0);
+	assert(errno == EISDIR);
+
 	memset(&vsm, 0, sizeof vsm);
 	vs = &vsm;