Frustratingly, using snprintf doesn't silence the warning. In my actual
case, both X and Y are chars of size MAXPATHLEN.
On Sun, May 31, 2020 at 2:32 PM NightStrike <nightstrike@xxxxxxxxx> wrote:
> I'm curious if this is a gcc bug or not. The warning I get is trying to
> highlight a real problem, but it's referring to a string literal as a
> directive, which I thought was just for the %XX printf commands. Given the
> following:
>
> #include <stdio.h>
>
> void f() {
> char x[4];
> char y[5];
> sprintf(x, "%s_%s", y, y);
> }
>
> $ gcc a.c -c -Wall
> a.c: In function 'f':
> a.c:6:16: warning: '_' directive writing 1 byte into a region of size
> between 0 and 4 [-Wformat-overflow=]
> 6 | sprintf(x, "%s_%s", y, y);
> | ^
> a.c:6:2: note: 'sprintf' output between 2 and 10 bytes into a destination
> of size 4
> 6 | sprintf(x, "%s_%s", y, y);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~
>
>
> I hope the fixed width display shows this correctly. The point is that
> the ^ points to the underscore, which is right, but the message calls the
> underscore a printf directive.
>
> Maybe I'm splitting hairs, but this confused me for a good half hour
> before I realized what was wrong.
>
>
