lib/stdio.in.h has this fragment:
/* _GL_ATTRIBUTE_FORMAT_PRINTF
indicates to GCC that the function takes a format string and arguments,
where the format string directives are the ones standardized by ISO C99
and POSIX. */
#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
# define _GL_ATTRIBUTE_FORMAT_PRINTF(formatstring_parameter, first_argument) \
_GL_ATTRIBUTE_FORMAT ((__gnu_printf__, formatstring_parameter,
first_argument
))
However, __gnu_printf__ is documented to refer to formats accepted by
the GNU C library, so it's potentially inappropriate on non-glibc
systems. In particular, MinGW builds that use this definition of
_GL_ATTRIBUTE_FORMAT emit bogus compilation warnings, like this one:
tfmt.c: In function 'foo':
tfmt.c:13:39: warning: format '%d' expects argument of type 'int', but
argument
3 has type 'long long int' [-Wformat=]
return make_formatted_string (name, "F%" PRIdMAX, count);
because PRIdMAX is defined as "I64d" in the MinGW headers, and
__gnu_printf__ evidently doesn't recognize that specifier.
What's more serious, using __gnu_printf__ will not flag the use of
%lld for formatting long long values, which will cause run-time
errors.
Using __ms_printf__ instead of __gnu_printf__ makes these problems go
away in a MinGW build.
Bottom line, I don't think __gnu_printf__ should be used on non-glibc
platforms.
Thanks.
