[Bug tree-optimization/97429] New: missing -Warray-bounds indexing past the end of a pointer to array

[Bug tree-optimization/97429] New: missing -Warray-bounds indexing past the end of a pointer to array

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97429

            Bug ID: 97429
           Summary: missing -Warray-bounds indexing past the end of a
                    pointer to array
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

The out of bounds index in fa(), ga(), and fp() is diagnosed as expected by
-Warray-bounds but the same bug in gp() is not.  They all should be.


$ cat xx.c && gcc -O2 -S -Wall xx.c
int fa (int a[3][5])
{ 
  return a[3][5];          // warning (good)
}

int ga (int a[3][5])
{
  int *p = &a[0][0];
  return p[15];            // warning (good)
}


int fp (int (*pa)[3][5])
{
  return (*pa)[3][5];      // warning (good)
}

int gp (int (*pa)[3][5])
{
  int *p = &(*pa)[0][0];   // missing warning
  return p[15];
}
xx.c: In function ‘fa’:
xx.c:3:14: warning: array subscript 5 is above array bounds of ‘int[5]’
[-Warray-bounds]
    3 |   return a[3][5];          // warning (good)
      |          ~~~~^~~
xx.c:1:13: note: while referencing ‘a’
    1 | int fa (int a[3][5])
      |         ~~~~^~~~~~~
xx.c: In function ‘ga’:
xx.c:9:11: warning: array subscript 15 is outside array bounds of ‘int[3]’
[-Warray-bounds]
    9 |   return p[15];            // warning (good)
      |          ~^~~~
xx.c:6:13: note: while referencing ‘a’
    6 | int ga (int a[3][5])
      |         ~~~~^~~~~~~
xx.c: In function ‘fp’:
xx.c:15:18: warning: array subscript 5 is above array bounds of ‘int[5]’
[-Warray-bounds]
   15 |   return (*pa)[3][5];      // warning (good)
      |          ~~~~~~~~^~~
xx.c:13:15: note: while referencing ‘pa’
   13 | int fp (int (*pa)[3][5])
      |         ~~~~~~^~~~~~~~~