[Bug c/77577] New: missing warnings about too few array elements

[drepper.fsp+rhbz at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77577

            Bug ID: 77577
           Summary: missing warnings about too few array elements
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: drepper.fsp+rhbz at gmail dot com
  Target Milestone: ---

With a declaration of 'f' as in the following code the function implementation
can assume that at least the given number of elements are available in the
array.  According to ISO C:

If the keyword static also appears within the [ and ] of the array type
derivation, then for each call to the function, the value of the corresponding
actual argument shall provide access to the first element of an array with at
least as many elements as specified by the size expression.


Given the following code gcc (in trunk and previous versions) does not emit a
warning.  It should be possible to emit one.  Especially with recent changes
which make __builtin_object_size usable even without optimization.


int f(int ss[static 5]);

int g() {
  int ar[2];
  return f(ar);
}