On Mon, Nov 03, 2014 at 01:41:20PM +0100, Lennart Poettering wrote: > On Mon, 03.11.14 13:12, David Herrmann (dh.herrm...@gmail.com) wrote: > > > Hi > > > > On Thu, Oct 16, 2014 at 11:43 PM, <philippedesw...@gmail.com> wrote: > > > From: Philippe De Swert <philippedesw...@gmail.com> > > > > > > Remove the following warning during the compilation: > > > src/libsystemd-terminal/grdev-drm.c: In function 'grdrm_card_hotplug': > > > src/libsystemd-terminal/grdev-drm.c:1087:45: warning: 'fb' may be used > > > uninitialized in this function [-Wmaybe-uninitialized] > > > src/libsystemd-terminal/grdev-drm.c:1035:19: note: 'fb' was declared here > > > --- > > > src/libsystemd-terminal/grdev-drm.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/src/libsystemd-terminal/grdev-drm.c > > > b/src/libsystemd-terminal/grdev-drm.c > > > index dba6db2..415755e 100644 > > > --- a/src/libsystemd-terminal/grdev-drm.c > > > +++ b/src/libsystemd-terminal/grdev-drm.c > > > @@ -1032,7 +1032,7 @@ error: > > > > > > static void grdrm_crtc_expose(grdrm_crtc *crtc) { > > > grdrm_pipe *pipe; > > > - grdrm_fb *fb; > > > + grdrm_fb *fb = NULL; > > > > Ewww, this is not nice. It does fix the warning, indeed, but the > > underlying problem is more generic. Lets look at this: > > > > int some_function(void **out) { > > ... > > r = ioctl(...); > > if (r < 0) > > return -errno; > > ... > > } > > > > gcc has no guarantee that "errno" is <0 if r is <0. Therefore, > > whenever it inlines those functions (-O2 etc.), it will spew a warning > > that "out" might be uninitialized if r<0 but errno==0. With -O0 gcc > > doesn't complain as it probably does not optimize across functions. > > However, with -O2 I get those warnings for "static" functions all the > > time. > > > > Not sure what to do here. I dislike initializing the pointer to NULL > > as it might hide other real warnings. I'd prefer something like: > > > > r = -SANE_ERRNO; > > > > with: > > > > #define SANE_ERRNO (abs(errno) ? : EMAGIC) > > > > ...not sure what we do in other places, though. Lennart? Tom? > > So far we went the simple way out and merged patches like the original > one you are replying to. > > Adding a call like this would make sane to me though: > > static inline negative_errno(void) { > return _likely_(errno > 0) ? -errno : -EINVAL; > } > > Which is then invoked as: > > return negative_errno(); > > or so... I like the assert more, because having errno <= 0 would be a signficant bug in the system, not something that we want to ever hide. So basically this is a way to tell the compiler what we already know, and assert is better.
I also filed https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61846, but without much response so far. Zbyszek _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel