[Bug tree-optimization/80776] -Wformat-overflow false positive for %d on integer bounded by __builtin_unreachable

["jsm28 at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80776

Joseph S. Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jsm28 at gcc dot gnu.org

--- Comment #2 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
The following, reduced from an unsuccessful attempt to avoid a spurious
-Wformat-overflow warning in glibc, produces a spurious warning with current
GCC and looks like the same bug or something very similar.

char buf[15];

void
f (int a, int b, int c, int d, int e, int f)
{
  if (a < -999 || a > 9999
      || b < 1 || b > 12
      || c < 1 || c > 31
      || d < 0 || d > 23
      || e < 0 || e > 59
      || f < 0 || f > 60)
    __builtin_unreachable ();
  __builtin_sprintf (buf, "%04d%02d%02d%02d%02d%02d", a, b, c, d, e, f);
}

u.c: In function 'f':
u.c:13:44: warning: '%02d' directive writing between 2 and 10 bytes into a
region of size 5 [-Wformat-overflow=]
   __builtin_sprintf (buf, "%04d%02d%02d%02d%02d%02d", a, b, c, d, e, f);
                                            ^~~~
u.c:13:27: note: directive argument in the range [0, 2147483647]
   __builtin_sprintf (buf, "%04d%02d%02d%02d%02d%02d", a, b, c, d, e, f);
                           ^~~~~~~~~~~~~~~~~~~~~~~~~~
u.c:13:27: note: directive argument in the range [0, 2147483647]
u.c:13:3: note: '__builtin_sprintf' output between 15 and 31 bytes into a
destination of size 15
   __builtin_sprintf (buf, "%04d%02d%02d%02d%02d%02d", a, b, c, d, e, f);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~