[Bug middle-end/77799] missing -Wformat-overflow warning on a trivial sprintf overflow with no directives

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77799

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
This bug was fixed along with the related pr77671 in r248035.  GCC 8.0 now
prints the following:

.c: In function ‘g’:
a.c:14:15: warning: too many arguments for format [-Wformat-extra-args]
   sprintf (d, "123", 0);
               ^~~~~
a.c: In function ‘f’:
a.c:9:18: warning: ‘123’ directive writing 3 bytes into a region of size 2
[-Wformat-overflow=]
   sprintf (d, "123");
                ~~^
a.c:9:3: note: ‘sprintf’ output 4 bytes into a destination of size 2
   sprintf (d, "123");
   ^~~~~~~~~~~~~~~~~~

;; Function f (f, funcdef_no=0, decl_uid=1819, cgraph_uid=0, symbol_order=1)

f ()
{
  <bb 2> [100.00%] [count: INV]:
  sprintf (&d, "123"); [tail call]
  return;

}


a.c: In function ‘g’:
a.c:14:18: warning: ‘123’ directive writing 3 bytes into a region of size 2
[-Wformat-overflow=]
   sprintf (d, "123", 0);
                ~~^
a.c:14:3: note: ‘sprintf’ output 4 bytes into a destination of size 2
   sprintf (d, "123", 0);
   ^~~~~~~~~~~~~~~~~~~~~

;; Function g (g, funcdef_no=1, decl_uid=1822, cgraph_uid=1, symbol_order=2)

g ()
{
  <bb 2> [100.00%] [count: INV]:
  sprintf (&d, "123", 0); [tail call]
  return;

}