[flashrom] [PATCH] Fix compilation with older MinGW versions

[Antonio Ospite]

The __MINGW_PRINTF_FORMAT constant has been defined back in 2012
https://sourceforge.net/p/mingw-w64/mingw-w64/ci/77bc5d6103b5fb9f59fbddab1583e69549913312/

However older toolchains are still around and some user reported the
following compilation failure:

  flash.h:336:1: error: '__MINGW_PRINTF_FORMAT' is an unrecognized format function  type [-Werror=format=]
    __attribute__((format(__MINGW_PRINTF_FORMAT, 2, 3)));

Fix this by defining the constant when it isn't already; the change does
not affect other compilers because it's guarded by "#ifdef __MINGW32__".

Setting  __MINGW_PRINTF_FORMAT to gnu_printf is exactly what newer MinGW
versions do when __USE_MINGW_ANSI_STDIO is defined, which it is in
flashrom Makefile.

Tested-by: Miklos Marton <martonmiklosqdev at gmail.com>
Signed-off-by: Antonio Ospite <ao2 at ao2.it>
---
 flash.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/flash.h b/flash.h
index a80a9c2..40a7f1a 100644
--- a/flash.h
+++ b/flash.h
@@ -360,6 +360,9 @@ int flashrom_print_cb(enum flashrom_log_level level, const char *fmt, va_list ap
 /* Let gcc and clang check for correct printf-style format strings. */
 int print(enum flashrom_log_level level, const char *fmt, ...)
 #ifdef __MINGW32__
+#  ifndef __MINGW_PRINTF_FORMAT
+#    define __MINGW_PRINTF_FORMAT gnu_printf
+#  endif
 __attribute__((format(__MINGW_PRINTF_FORMAT, 2, 3)));
 #else
 __attribute__((format(printf, 2, 3)));
-- 
2.16.2