Re: PATCH: Don't crash when math recursion limit is exceeded

[Peter Stephenson <p.w.stephenson@xxxxxxxxxxxx>]

On Sun, 10 Mar 2013 13:06:37 +0100
Mikael Magnusson <mikachu@xxxxxxxxx> wrote:
> This used to never trigger for me when compiling in debug mode, but I
> finally had better luck today and tracked it down.
> 
> *ep seems to already be NULL, but I couldn't quite figure out where it
> was set to NULL so I figured it can't hurt to make it explicitly NULL
> at that point. I suppose setting *ep = ""; would also work (without the
> second hunk)?

Another way of doing it would probably be to set "*ep = s", which is
consistent with what *ep is supposed to be doing.

If you set it to NULL it's probably safest to change the value returned
by the other calls of mathevall() around line 960 pre-patch, which also
outputs the "bad math expression" error.  I don't see why they shouldn't
be fully consistent; zerr() already tests for errflag, so they shouldn't
need to test for that, but either neither or both should.

-- 
Peter Stephenson <p.w.stephenson@xxxxxxxxxxxx>
Web page now at http://homepage.ntlworld.com/p.w.stephenson/


 
> ---
>  Src/math.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/Src/math.c b/Src/math.c
> index f8a4eef..43cede9 100644
> --- a/Src/math.c
> +++ b/Src/math.c
> @@ -362,6 +362,7 @@ mathevall(char *s, enum prec_type prec_tp, char **ep)
>      if (mlevel >= MAX_MLEVEL) {
>  	xyyval.type = MN_INTEGER;
>  	xyyval.u.l = 0;
> +	*ep = NULL;
>  
>  	zerr("math recursion limit exceeded");
>  
> @@ -1352,7 +1353,7 @@ matheval(char *s)
>      }
>      x = mathevall(s, MPREC_TOP, &junk);
>      mtok = xmtok;
> -    if (*junk)
> +    if (junk && *junk)
>  	zerr("bad math expression: illegal character: %c", *junk);
>      return x;
>  }
> -- 
> 1.7.10.GIT