[Bug c/112833] New: Missing warnings on restrict misuse

[Bug c/112833] New: Missing warnings on restrict misuse

[alx at kernel dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112833

            Bug ID: 112833
           Summary: Missing warnings on restrict misuse
           Product: gcc
           Version: 13.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alx at kernel dot org
  Target Milestone: ---

Reproducer:


$ cat restrict.c 
long bogus_strtol(const char *restrict s, char **restrict ep, int base);

int
main(void)
{
        char buf[3] = "foo";
        char *p = buf;

        bogus_strtol(p, &p, -42);
}

long
bogus_strtol(const char *restrict s, char **restrict ep, int base)
{
        **ep = *s;
        return base;
}
$ gcc -Wall -Wextra restrict.c -fanalyzer
$ gcc -Wall -Wextra restrict.c -fanalyzer -O3


I'd expect two -Wrestrict warnings, one at call site, and another at `**ep =
*s;`.

BTW, of course, I'd also expect a warning at calls to strtol(3), which I
consider has a wrong use of restrict in the prototype.

Original report at gcc-help@:
<https://inbox.sourceware.org/gcc-help/ZWyw72QNLhzG874z@debian/T/#t>

[Bug c/112833] Missing warnings on restrict misuse

[alx at kernel dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112833

--- Comment #1 from Alejandro Colomar <alx at kernel dot org> ---
Oops, in the reproducer from above, I should only expect a warning at call
site.  The definition is correct, since all parameters are restrict, so it's
free to copy one to the other.

Here's a reproducer where the call is fine, but the definition is wrong, and
the compiler doesn't realize:


$ cat restrict.c 
#include <string.h>

long bogus2_strtol(const char *s, char **restrict ep, int base);

int
main(void)
{
        char buf[3] = "foo";
        char *p = buf;

        bogus2_strtol(p, &p, -42);
}

long
bogus2_strtol(const char *s, char **restrict ep, int base)
{
        memcpy(*ep, s, 1);
        return base;
}
$ gcc -Wall -Wextra restrict.c -fanalyzer
$ gcc -Wall -Wextra restrict.c -fanalyzer -O3