[Bug c/38443] New: scoping problems with identically named identifiers

["lc235951 at students dot mimuw dot edu dot pl" <gcc-bugzilla at gcc dot gnu dot org>]

The following program gives -1208725329 0 as output, and no warnings are
generated despite all warnings being turned on (-W -Wall).

#include <stdio.h>

int main()
{
  int x = 0;
  {
    int x = x - 1;
    printf("%d\n", x);
  }
  printf("%d\n", x);
  return 0;
}

I am not sure as to the exact scoping rules employed by C in this case, and I
couldn't find a passage in the ISO C standard which would unambiguously
indicate the right version (probably because I'm not thoroughly familiar with
the standard and didn't want to read the whole document).

Even if this behaviour is correct I think there should at least be a warning.

Anyway, whatever the C standard says, it would be much more useful if the
second x were assigned -1 in this case. I actually came upon this problem in a
complicated macro expression (involving a macro inside a macro, etc.) where it
was not apparent that the names were the same. The macro would work regardless
of the names if the behaviour of GCC was as I expected it to be.


-- 
           Summary: scoping problems with identically named identifiers
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: lc235951 at students dot mimuw dot edu dot pl
 GCC build triplet: i486-linux-gnu
  GCC host triplet: i486-linux-gnu
GCC target triplet: i486-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38443