[Bug middle-end/48560] [4.6/4.7 Regression] -Warray-bounds fails to detect the out of bound array access

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48560

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
                 CC|                            |msebor at gcc dot gnu.org
      Known to work|                            |4.5.3, 5.1.0
             Blocks|                            |56456
         Resolution|WONTFIX                     |FIXED
      Known to fail|                            |4.7.4

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
The code is diagnosed by recent versions of GCC:

$ cat pr48560.c && gcc -O2 -S -Wall pr48560.c
char
foo1 (int i)
{
  static char s[] = "foo";
  switch (i)
  {
  case 30:
    return s[30];
  }
  return s[i];
}
pr48560.c: In function ‘foo1’:
pr48560.c:8:13: warning: array subscript 30 is above array bounds of ‘char[4]’
[-Warray-bounds]
     return s[30];
            ~^~~~

Bisection points to r213045 (gcc 5.1.0) as the commit that restored the
warning.  Let me add the test case to the test suite and change the resolution
to fixed.

r213045 | rguenth | 2014-07-25 03:44:57 -0400 (Fri, 25 Jul 2014) | 22 lines

2014-07-25  Richard Biener  <rguenther@suse.de>

        PR middle-end/61762
        PR middle-end/61894
        * fold-const.c (native_encode_int): Add and handle offset
        parameter to do partial encodings of expr.
        (native_encode_fixed): Likewise.
        (native_encode_real): Likewise.
        (native_encode_complex): Likewise.
        (native_encode_vector): Likewise.
        (native_encode_string): Likewise.
        (native_encode_expr): Likewise.
        * fold-const.c (native_encode_expr): Add offset parameter
        defaulting to -1.
        * gimple-fold.c (fold_string_cst_ctor_reference): Remove.
        (fold_ctor_reference): Handle all reads from tcc_constant
        ctors.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56456
[Bug 56456] [meta-bug] bogus/missing -Warray-bounds