[Bug middle-end/13400] New: Compiled code crashes storing to read-only location

["hebisch at math dot uni dot wroc dot pl" <gcc-bugzilla at gcc dot gnu dot org>]

The following program:

typedef struct {int c, l; char ch[3];} pstr;
const pstr ao = {2, 2, "OK"};
const pstr * const a = &ao;

int main(void)
{
        if (a->ch[a->l]) {
                ((char *)a->ch)[a->l] = 0;
        }
        return 0;
}

segfaults when compiled using `-O' (or better optimisation).
Without optimisation the store is not executed and the program
runs fine.

I tried CVS gcc (updated DEC 14, 04:28 CET 2003) on Athlon-XP
running Debian Woody (configured using '--enable-languages=c'
as the only option). The problem does not appear in 20031029
snapshot, but is present in 20031105 snapshot.

By the way, my original problem is in GNU Pascal. Constant Pascal
strings are stored in .rodata section and compiler makes sure that
the string is null terminated. On the other hand variable strings
need not be null terminated. When convering Pascal strings to C
strings GPC generates code to null terminate the strings which are
not already null terminated. The C program above tries to reproduce
the code GPC produces.

-- 
           Summary: Compiled code crashes storing to read-only location
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hebisch at math dot uni dot wroc dot pl
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13400