On Tue, Dec 13, 2022 at 11:16 AM Alejandro Colomar via Gcc <gcc@gcc.gnu.org> wrote: > > > > On 12/13/22 20:08, Alejandro Colomar wrote: > > Hi! > > > > For the following program: > > > > > > $ cat buf.c > > #include <stdio.h> > > > > int main(void) > > { > > char *p, buf[5]; > > > > p = buf + 6; > > printf("%p\n", p); > > } > > > > > > There are no warnings in gcc, as I would expect: > > I just re-read my text, and it is ambiguous. I meant that I expect warnings.
GCC only warns during VRP which is only enabled at -O2: <source>:8:12: warning: array subscript 6 is outside array bounds of 'char[5]' [-Warray-bounds=] 8 | p = buf + 6; | ~~^~~~~~~~~ <source>:6:19: note: at offset 6 into object 'buf' of size 5 6 | char *p, buf[5]; | ^~~ Thanks, Andrew > > > > > > $ gcc -Wall -Wextra buf.c -O0 > > > > Clang does warn, however: > > > > $ clang -Weverything -Wall -Wextra buf.c -O0 > > buf.c:8:17: warning: format specifies type 'void *' but the argument > > has > > type 'char *' [-Wformat-pedantic] > > printf("%p\n", p); > > ~~ ^ > > %s > > buf.c:7:6: warning: the pointer incremented by 6 refers past the end > > of the > > array (that contains 5 elements) [-Warray-bounds-pointer-arithmetic] > > p = buf + 6; > > ^ ~ > > buf.c:5:2: note: array 'buf' declared here > > char *p, buf[5]; > > ^ > > 2 warnings generated. > > > > Cheers, > > > > Alex > > > > > > -- > <http://www.alejandro-colomar.es/>