[Bug middle-end/89977] New: missing -Wstringop-overflow with an out-of-bounds int128_t range

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89977

            Bug ID: 89977
           Summary: missing -Wstringop-overflow with an out-of-bounds
                    int128_t range
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

Additional testing of the patch for pr89957 exposed the following:

GCC diagnoses the buffer overflow in f() below but fails to diagnose the same
buffer overflow in g().  The get_range_info() function returns VR_VARYING for
the int128_t variable in g().

$ cat z.c && gcc -S -O2 -Wall -Wextra -fdump-tree-optimized=/dev/stdout z.c
char a[3];

__attribute__ ((noipa))
void f (int n)
{
  if (n < 7)
    n = 7;
  __builtin_memset (a, 0, n);
}

__attribute__ ((noipa))
void g (__int128_t n)
{
  if (n < 7)
    n = 7;
  __builtin_memset (a, 0, n);
}
z.c: In function ‘f’:
z.c:8:3: warning: ‘__builtin_memset’ forming offset [4, 7] is out of the bounds
[0, 3] of object ‘a’ with type ‘char[3]’ [-Warray-bounds]
    8 |   __builtin_memset (a, 0, n);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~
z.c:1:6: note: ‘a’ declared here
    1 | char a[3];
      |      ^

;; Function f (f, funcdef_no=0, decl_uid=1907, cgraph_uid=1, symbol_order=1)

__attribute__((noipa, noinline, noclone, no_icf))
f (int n)
{
  long unsigned int _1;

  <bb 2> [local count: 1073741824]:
  n_3 = MAX_EXPR <n_2(D), 7>;
  _1 = (long unsigned int) n_3;
  __builtin_memset (&a, 0, _1); [tail call]
  return;

}



;; Function g (g, funcdef_no=1, decl_uid=1910, cgraph_uid=2, symbol_order=2)

__attribute__((noipa, noinline, noclone, no_icf))
g (__int128 n)
{
  long unsigned int _1;

  <bb 2> [local count: 1073741824]:
  n_3 = MAX_EXPR <n_2(D), 7>;
  _1 = (long unsigned int) n_3;
  __builtin_memset (&a, 0, _1); [tail call]
  return;

}