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From: "eyalroz1 at gmx dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c/102936] New: Excessive warnings about passing NULL for an
 "%s" specifier
Date: Mon, 25 Oct 2021 18:27:11 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102936

            Bug ID: 102936
           Summary: Excessive warnings about passing NULL for an "%s"
                    specifier
           Product: gcc
           Version: 10.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: eyalroz1 at gmx dot com
  Target Milestone: ---

Consider the following program:

    #include <stddef.h>=20

    __attribute__((format(__printf__, 2, 3)))
    int sprintf_(char* buffer, const char* format, ...)
    {
        (void) buffer;
        (void) format;
        return 0;
   }=20

    int main() {
        char buffer[100];
        return sprintf_(buffer, "%s", NULL);
    }

when compiled with `-W -Wall`, we get two warnings:

    a.c:15:28: warning: format =E2=80=98%s=E2=80=99 expects argument of typ=
e =E2=80=98char *=E2=80=99, but
argument 3 has type =E2=80=98void *=E2=80=99 [-Wformat=3D]
    a.c:15:9: warning: =E2=80=98%s=E2=80=99 directive argument is null [-Wf=
ormat-overflow=3D]

The second warning seems legit. However - I don't think I should be getting=
 the
first warning. If I can write:

    char* ptr =3D NULL;

and not get a type warning, I don't see why I should get one for passing NU=
LL
to the function.=