[Bug tree-optimization/104657] New: array subscript 0 is outside array bounds

[christophm30 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104657

            Bug ID: 104657
           Summary: array subscript 0 is outside array bounds
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: christophm30 at gmail dot com
  Target Milestone: ---

Compiling the following code:

void foo(unsigned long v)
{
        volatile unsigned long *p;
        p = (void *)0x8;
        *p = v;
}

with GCC master and "-O2 -Wall" results in the following warning:

$ gcc -O2 -Wall  -c array_subscript_0.c 
array_subscript_0.c: In function 'foo':
array_subscript_0.c:5:9: warning: array subscript 0 is outside array bounds of
'volatile long unsigned int[0]' [-Warray-bounds]
    5 |         *p = v;
      |         ^~

This warning is unexpected and is not triggered by earlier versions of GCC.

Possibly related: pr101977