[Bug optimization/12640] [tree-ssa] strlen builtin causes stack overflow building tk

["steven at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From steven at gcc dot gnu dot org  2003-11-12 18:22 -------
Small, smaller, smallest... 
 
int i; 
static void 
SendEventProc (char *resultString) 
{ 
  char *p; 
 
  resultString = ""; 
  while (*p == '-') 
    { 
      if (p[2] == ' ') 
        { 
          resultString = p + 3; 
        } 
    } 
  for (;;) 
    { 
      i = strlen (resultString) + 1; 
    } 
} 
 
The thing is that we have this PHI: 
resultString_1 = PHI <(char *)""(0), resultString_1(1), resultString_9(2)>; 
 
and we go on to try and get the lentgh of all the PHI args, by looking at the 
DEF stmts of each PHI arg... and resultString_1 has itself as an argument.  
There's your infinite loop. 
 
Probably need a patch like this (perhaps just return NULL_TREE, but I don't 
think we have to...)  No time to test or think, so I've just put it here so 
that it doesn't get lost in my messy file system. 
 
ndex: tree-ssa-ccp.c 
=================================================================== 
RCS file: /cvs/gcc/gcc/gcc/Attic/tree-ssa-ccp.c,v 
retrieving revision 1.1.2.108 
diff -c -3 -p -r1.1.2.108 tree-ssa-ccp.c 
*** tree-ssa-ccp.c      11 Nov 2003 18:04:46 -0000      1.1.2.108 
--- tree-ssa-ccp.c      12 Nov 2003 18:20:25 -0000 
*************** get_strlen (tree arg) 
*** 1922,1928 **** 
          arg_len = prev_arg_len = NULL_TREE; 
          for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++) 
            { 
!             arg_len = get_strlen (PHI_ARG_DEF (def_stmt, i)); 
              if (arg_len == NULL_TREE) 
                return NULL_TREE; 
 
--- 1922,1939 ---- 
          arg_len = prev_arg_len = NULL_TREE; 
          for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++) 
            { 
!             tree arg_def_stmt = PHI_ARG_DEF (def_stmt, i); 
! 
!             /* If this PHI has itself as an argument, we cannot 
!                determine the string length of this argument.  However, 
!                if we can find a constant string length for the other 
!                PHI args then we can still be sure that this is a 
!                constant string length.  So be optimistic and just 
!                continue with the next argument.  */ 
!             if (arg_def_stmt == def_stmt) 
!               continue; 
! 
!             arg_len = get_strlen (arg_def_stmt); 
              if (arg_len == NULL_TREE) 
                return NULL_TREE; 
 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12640