warnings.c : fixes dereference to null warning

Change-Id: I03cceb4b92b7362e90f3ea61342341246b9a11ab

tools_common.h

@@ -103,17 +103,25 @@ struct VpxInputContext {
 extern "C" {
 #endif
 
+#if defined(__GNUC__)
+#define VPX_NO_RETURN __attribute__((noreturn))
+#else
+#define VPX_NO_RETURN
+#endif
+
 /* Sets a stdio stream into binary mode */
 FILE *set_binary_mode(FILE *stream);
 
-void die(const char *fmt, ...);
-void fatal(const char *fmt, ...);
+void die(const char *fmt, ...) VPX_NO_RETURN;
+void fatal(const char *fmt, ...) VPX_NO_RETURN;
 void warn(const char *fmt, ...);
 
-void die_codec(vpx_codec_ctx_t *ctx, const char *s);
+void die_codec(vpx_codec_ctx_t *ctx, const char *s) VPX_NO_RETURN;
 
 /* The tool including this file must define usage_exit() */
-void usage_exit();
+void usage_exit() VPX_NO_RETURN;
+
+#undef VPX_NO_RETURN
 
 int read_yuv_frame(struct VpxInputContext *input_ctx, vpx_image_t *yuv_frame);