https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91929
--- Comment #13 from rguenther at suse dot de <rguenther at suse dot de> --- On Fri, 18 Oct 2019, dimhen at gmail dot com wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91929 > > Dmitry G. Dyachenko <dimhen at gmail dot com> changed: > > What |Removed |Added > ---------------------------------------------------------------------------- > CC| |dimhen at gmail dot com > > --- Comment #12 from Dmitry G. Dyachenko <dimhen at gmail dot com> --- > I see new warnings -Wuninitialized and -Wmaybe-uninitialized after r276993 > > r276992 no warnings > r276993 warnings > > $ cat x_3.i > int *a; > int b, d; > > int g() { > int *c; > int e[6]; > int f = 1; > if (0) > goto cd; > c = 0; > for (; d; d++) > *e = 1 ^ *(c + 1); > if (f) > for (b = 0;;) > a[0] = e[b]; > cd: > return 0; > } > > $ ~/arch-gcc/gcc_276993/bin/gcc -fpreprocessed -O2 -Wall -c x_3.i > > x_3.i: In function ‘g’: > x_3.i:15:15: warning: ‘e[0]’ may be used uninitialized in this function > [-Wmaybe-uninitialized] > 15 | a[0] = e[b]; > | ~^~~ If d is zero then e[0] will be loaded uninitialized. PRE exposes this to the uninit machinery which previously gave up for loops by commoning e[b] with the set in the loop plus inserting a load from e[0] on the path not coming from the loop. I guess previously the uninit pass didn't emit warnings for the load because it had no location. > $ cat x.i > typedef struct { > int a[0]; > } c; > typedef struct { > c d; > } * e; > e a; > void f(void); > void f() { > int c[1]; > for (;;) { > unsigned long d[0]; > int b, g, h = b = h; > unsigned long *e = d; > for (; g; ++g) > e[g] = 0; > *a->d.a = *c; > } > } > > $ ~/arch-gcc/gcc_276993/bin/gcc -fpreprocessed -O2 -Wall -c x.i > x.i: In function ‘f’: > x.i:17:13: warning: ‘c[0]’ is used uninitialized in this function > [-Wuninitialized] > 17 | *a->d.a = *c; > | ~~~~~~~~^~~~ This is the same (and g is not initialized here as well)
