windows: fix format string attributes on MinGW

MinGW maps the "printf" format string archetype to the non-standard
MSVCRT functions, even if __USE_MINGW_ANSI_STDIO is defined and set
to 1. We need to use "gnu_printf" to use the format strings as provided
by vsnprintf and similar functions to get correct warnings.

Since "gnu_printf" isn't necessarily available on other GCC compatible
compilers (such as clang), do this only on MinGW.

1 files changed, 20 insertions, 0 deletions

diff --git a/mpcommon.h b/mpcommon.h
index fd520eacf6..2ff66fed40 100644
--- a/mpcommon.h
+++ b/mpcommon.h
@@ -31,6 +31,26 @@
 #define MP_RESIZE_ARRAY(ctx, p, count) do {     \
         p = talloc_realloc_size((ctx), p, (count) * sizeof(p[0])); } while (0)
 
+#ifdef __GNUC__
+
+/** Use gcc attribute to check printf fns.  a1 is the 1-based index of
+ * the parameter containing the format, and a2 the index of the first
+ * argument. **/
+#ifdef __MINGW32__
+// MinGW maps "printf" to the non-standard MSVCRT functions, even if
+// __USE_MINGW_ANSI_STDIO is defined and set to 1. We need to use "gnu_printf",
+// which isn't necessarily available on other GCC compatible compilers.
+#define PRINTF_ATTRIBUTE(a1, a2) __attribute__ ((format (gnu_printf, a1, a2)))
+#else
+#define PRINTF_ATTRIBUTE(a1, a2) __attribute__ ((format (printf, a1, a2)))
+#endif
+
+#else
+
+#define PRINTF_ATTRIBUTE(a1, a2)
+
+#endif
+
 extern const char *mplayer_version;
 
 #endif /* MPLAYER_MPCOMMON_H */