On Wed, 13 Feb 2008, Michal Marek wrote:
Hi,
Hi,
gcc allows to mark variadic functions that expect a terminating NULL as
such and issues a warning if the caller doesn't pass the NULL. A similar
mechanism is available for printf-like functions. What about using this
for the few variadic functions in the rpmlib API? It would help to catch
some mistakes at compile-time rather than at run-time, e.g:
char *test1 = rpmExpand("%_sourcedir");
char *test2 = rpmExpand("%_topdir", " ");
$ gcc -Wall -I ./include -c test.c
test.c: In function 'main':
test.c:9: warning: not enough variable arguments to fit a sentinel
test.c:10: warning: missing sentinel in function call
Attached are two patches, the first one marks rpmExpand() and
rpmGetPath() with __attribute__((sentinel)) for gcc 4.0+ and rpmlog()
with __attribute__((format (printf, 2, 3))). The second patch silences
warnings in rpmlog() calls that now show up.
Comments?
Considering the amount of warnings the extra checking already found,
I'd say there's little doubt of it's usefulness.
I also have little doubt that there are a number of other gcc extensions
too that would be useful. So instead of littering the headers with
#if defined(__GNUC__) && __GNUC__ >= <someversion>
#endif
everywhere, might as well add macros for them centrally someplace,
similarly to what glib's gmacros.h does:
#if __GNUC__ >= 4
#define G_GNUC_NULL_TERMINATED __attribute__((__sentinel__))
#else
#define G_GNUC_NULL_TERMINATED
#endif
..etc. Maybe just grab a copy of gmacros.h instead of reinventing the
wheel...
- Panu -
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