Test if exit() works in a multi-threaded process.

Commit 2d91c7d385 fixed this issue.

regress/Makefile

@@ -18,6 +18,7 @@ TESTS:=\
 test-fmemopen \
 test-pthread-argv \
 test-pthread-basic \
+test-pthread-main-exit \
 test-pthread-main-join \
 test-pthread-once \
 test-pthread-self \

regress/test-pthread-main-exit.c

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2016 Jonas 'Sortie' Termansen.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * test-pthread-main-exit.c
+ * Test if exit() works in a multi-threaded process.
+ */
+
+#include <pthread.h>
+#include <sched.h>
+#include <stdbool.h>
+
+#include "test.h"
+
+void* thread_routine(void* ctx)
+{
+	(void) ctx;
+	while ( true )
+		sched_yield();
+}
+
+int main(void)
+{
+	int errnum;
+	pthread_t thread;
+	if ( (errnum = pthread_create(&thread, NULL, &thread_routine, NULL)) )
+		test_error(errnum, "pthread_create");
+	sched_yield();
+	exit(0);
+}