avutil/tests: Add cpu_init.c to check whether the one-time initialization in av_get_cpu_flags() has data races.

Co-author: Dmitry Vyukov of Google

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavutil/Makefile

@@ -187,6 +187,7 @@ TESTPROGS = adler32                                                     \
             camellia                                                    \
             color_utils                                                 \
             cpu                                                         \
+            cpu_init                                                    \
             crc                                                         \
             des                                                         \
             dict                                                        \

libavutil/tests/cpu_init.c

@@ -0,0 +1,72 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/*
+ * This test program tests whether the one-time initialization in
+ * av_get_cpu_flags() has data races.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "config.h"
+
+#include "libavutil/cpu.h"
+#include "libavutil/thread.h"
+
+#if HAVE_PTHREADS
+static void *thread_main(void *arg)
+{
+    int *flags = arg;
+
+    *flags = av_get_cpu_flags();
+    return NULL;
+}
+#endif
+
+
+int main(int argc, char **argv)
+{
+#if HAVE_PTHREADS
+    int cpu_flags1;
+    int cpu_flags2;
+    int ret;
+    pthread_t thread1;
+    pthread_t thread2;
+
+    if ((ret = pthread_create(&thread1, NULL, thread_main, &cpu_flags1))) {
+        fprintf(stderr, "pthread_create failed: %s.\n", strerror(ret));
+        return 1;
+    }
+    if ((ret = pthread_create(&thread2, NULL, thread_main, &cpu_flags2))) {
+        fprintf(stderr, "pthread_create failed: %s.\n", strerror(ret));
+        return 1;
+    }
+    pthread_join(thread1, NULL);
+    pthread_join(thread2, NULL);
+
+    if (cpu_flags1 < 0)
+        return 2;
+    if (cpu_flags2 < 0)
+        return 2;
+    if (cpu_flags1 != cpu_flags2)
+        return 3;
+#endif
+
+    return 0;
+}