Re: Util/helpfiles - problem with provided example

[Peter Stephenson <pws@csr.com>]

Peter Stephenson wrote:
> Michael Prokop wrote:
> > man () {
> >        man $1                                     # this is the original
> >   }
> > $ man zsh
> 
> > Segmentation fault
> 
> This isn't very nice.  Should we turn on --enable-max-function-depth by
> default?  The default for --enable-max-function-depth=yes is 4096 which
> isn't going to hurt most people.  Or should we make it configurable
> internally with a sensible default?

More investigation reveals a further problem.  There's an arbitrary
debugging check when unreferencing the function that it hasn't been
referenced more than 256 times.  This needs to be the function depth if
that is defined plus 1 (to allow for the original function struture).
I've added a few on for fuzz.  Presumably the test is meaningless if
there is no function depth limit.

If you try this with a the default function depth limit, it's
interesting to note that the error message is printed almost straight
away, while the prompt takes a while to return.  I wonder if freeing
things up is slower than necessary?

Index: Src/parse.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/parse.c,v
retrieving revision 1.46
diff -u -r1.46 parse.c
--- Src/parse.c	28 Jun 2004 15:38:14 -0000	1.46
+++ Src/parse.c	28 Jul 2004 10:18:28 -0000
@@ -2168,7 +2168,10 @@
 	/* paranoia */
 	DPUTS(p->nref > 0 && (p->flags & EF_HEAP), "Heap EPROG has nref > 0");
 	DPUTS(p->nref < 0 && !(p->flags & EF_HEAP), "Real EPROG has nref < 0");
-	DPUTS(p->nref < -1 || p->nref > 256, "Uninitialised EPROG nref");
+	DPUTS(p->nref < -1, "Uninitialised EPROG nref");
+#ifdef MAX_FUNCTION_DEPTH
+	DPUTS(p->nref > MAX_FUNCTION_DEPTH + 10, "Overlarge EPROG nref");
+#endif
 	if (p->nref > 0 && !--p->nref) {
 	    for (i = p->npats, pp = p->pats; i--; pp++)
 		freepatprog(*pp);

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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