Add Dave's explainations of why certain pointers are always non-NULL,

and assert() that it is true.

p4raw-id: //depot/perl@27866

diff --git a/regexec.c b/regexec.c
index 4d0388d..50f164f 100644 (file)
--- a/regexec.c
+++ b/regexec.c
@@ -3531,6 +3531,18 @@ S_regmatch(pTHX_ const regmatch_info *reginfo, regnode *prog)
                /* No need to save/restore up to this paren */
                I32 parenfloor = scan->flags;
 
+               /* Dave says:
+                  
+                  CURLYX and WHILEM are always paired: they're the moral
+                  equivalent of pp_enteriter anbd pp_iter.
+
+                  The only time next could be null is if the node tree is
+                  corrupt. This was mentioned on p5p a few days ago.
+
+                  See http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-04/msg00556.html
+                  So we'll assert that this is true:
+               */
+               assert(next);
                if (OP(PREVOPER(next)) == NOTHING) /* LONGJMP */
                    next += ARG(next);
                /* XXXX Probably it is better to teach regpush to support
@@ -3570,6 +3582,16 @@ S_regmatch(pTHX_ const regmatch_info *reginfo, regnode *prog)
                 * that we can try again after backing off.
                 */
 
+               /* Dave says:
+
+                  st->cc gets initialised by CURLYX ready for use by WHILEM.
+                  So again, unless somethings been corrupted, st->cc cannot
+                  be null at that point in WHILEM.
+                  
+                  See http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-04/msg00556.html
+                  So we'll assert that this is true:
+               */
+               assert(st->cc);
                st->u.whilem.lastloc = st->cc->u.curlyx.lastloc; /* Detection of 0-len. */
                st->u.whilem.cache_offset = 0;
                st->u.whilem.cache_bit = 0;