From: Daniel Elstner <redacted>
Date: Sun, 13 Sep 2015 13:07:54 +0000 (+0200)
Subject: Build: Force ISO-conforming format syntax on MinGW
X-Git-Tag: libsigrok-0.4.0~305
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=7419638d4c5d21dadccfd8f234c5671c5330dc33;p=libsigrok.git

Build: Force ISO-conforming format syntax on MinGW

On MinGW, two implementations of printf() are available: either
the Microsoft native one or a standard-conforming replacement from
gnulib. Since we build in C99 mode, headers such as <inttypes.h>
already select the standard-conforming variant. However, MinGW's
GCC does not seem to know about this and assumes MS-style format
syntax by default, which triggers a lot of wrong warnings.

Thus, on MinGW, explicitly decorate sr_log() with the gnu_printf
format flavor attribute. Also use GLib's printf replacements in
the logging implementation to make sure we link to a conforming
printf on any platform, independently of the compiler flags.

This gets rid of the mistaken -Wformat warnings for sr_log(), but
does not cover functions such as g_strdup_printf() which do not
explicitly specify the gnu_printf flavor in the format attribute.
This can be overcome by adding "-D__printf__=__gnu_printf__" to
CPPFLAGS, but it would be inappropriate for libsigrok to define
this on its own.
---

diff --git a/src/libsigrok-internal.h b/src/libsigrok-internal.h
index b4280325..465f2421 100644
--- a/src/libsigrok-internal.h
+++ b/src/libsigrok-internal.h
@@ -595,7 +595,16 @@ struct drv_context {
 
 /*--- log.c -----------------------------------------------------------------*/
 
+#if defined(G_OS_WIN32) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4))
+/*
+ * On MinGW, we need to specify the gnu_printf format flavor or GCC
+ * will assume non-standard Microsoft printf syntax.
+ */
+SR_PRIV int sr_log(int loglevel, const char *format, ...)
+		__attribute__((__format__ (__gnu_printf__, 2, 3)));
+#else
 SR_PRIV int sr_log(int loglevel, const char *format, ...) G_GNUC_PRINTF(2, 3);
+#endif
 
 /* Message logging helpers with subsystem-specific prefix string. */
 #define sr_spew(...)	sr_log(SR_LOG_SPEW, LOG_PREFIX ": " __VA_ARGS__)
diff --git a/src/log.c b/src/log.c
index 87c77971..db5a3fd4 100644
--- a/src/log.c
+++ b/src/log.c
@@ -20,6 +20,7 @@
 
 #include <stdarg.h>
 #include <stdio.h>
+#include <glib/gprintf.h>
 #include <libsigrok/libsigrok.h>
 #include "libsigrok-internal.h"
 
@@ -178,13 +179,13 @@ static int sr_logv(void *cb_data, int loglevel, const char *format, va_list args
 		seconds = rest_us / G_TIME_SPAN_SECOND;
 		microseconds = rest_us % G_TIME_SPAN_SECOND;
 
-		ret = fprintf(stderr, "sr: [%.2" PRIu64 ":%.2u.%.6u] ",
+		ret = g_fprintf(stderr, "sr: [%.2" PRIu64 ":%.2u.%.6u] ",
 				minutes, seconds, microseconds);
 	} else {
 		ret = fputs("sr: ", stderr);
 	}
 
-	if (ret < 0 || vfprintf(stderr, format, args) < 0
+	if (ret < 0 || g_vfprintf(stderr, format, args) < 0
 			|| putc('\n', stderr) < 0)
 		return SR_ERR;