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 b42803258d8b624275ab8b3a00e3fe385e6642a2..465f24213b0935d319c890be76918e2e370f43e0 100644 (file)
--- 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 87c77971ffed8c360edc3643aec169a30dbfd83a..db5a3fd42f98ab94beff12983f1809e3f3ed3b0c 100644 (file)
--- 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;