http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39438
--- Comment #6 from D. Hugh Redelmeier <hugh at mimosa dot com> ---
Responding to Comment 5 by Manuel López-Ibáñez:
Thanks for looking at this.
> Could you produce a complete testcase
===
/* compile with -c -Wformat -Werror=format-nonliteral */
#include <time.h>
extern void prettynow(char *buf, size_t buflen, const char *fmt, struct tm *t)
__attribute__ ((format (__strftime__, 3, 0)));
void prettynow(char *buf, size_t buflen, const char *fmt, struct tm *t)
{
strftime(buf, buflen, fmt, t);
}
===
> The best would be to include only the definitions of the types that you need
> > and declare as 'extern' library functions that you use to avoid including
> headers.
I didn't do this part. My excuses: the type declarations are not portable but
the example should be; the solution might be in fixing headers; this way is
shorter too.
> If you can produce another similar example that works with printf, that would
> also help.
I don't think that printf is similar enough. A strftime format doesn't
interact with varargs in a complex and problematic way. A string, on its own,
is or is not a valid strftime format; a string is only a valid printf format
when considered with the argument list.
If an arg is marked as a const char * (i.e. unchanging) and has the strftime
format attribute, it should be accepted as if it were a literal strftime
argument. After all, the necessary checking would have been done at this
routine's points of call.
