Re: [Valgrind-users] Patch to fix suppression-file parser

[Jeffrey S. <fe...@xi...>]

On Mon, 2003-05-12 at 15:59, Nicholas Nethercote wrote:
> On 8 May 2003, Jeffrey Stedfast wrote:
> 
> > If the number of callers specified in the suppression rule is >=
> > VG_N_SUPP_CALLERS, the parser gets confused.
> >
> > The attached patch fixes this condition.
> 
> I wouldn't say it gets confused;  it's a syntax error, because
> suppressions don't support stack traces with more than four entries.
> Admittedly the error message isn't great, but I don't think this is a
> behaviour that needs fixing.

sure, except that it breaks on 4 callers ;-)

the current parser only accepts 3, the 4th line MUST be a "}" line or
the next pass thru the outer loop will encounter the "}" and abort since
it doesn't match "{"

      for (i = 0; i < VG_N_SUPP_CALLERS; i++) {
         eof = VG_(get_line) ( fd, buf, N_BUF );
         if (eof) goto syntax_error;
         if (i > 0 && STREQ(buf, "}")) 
            break;
         supp->caller[i] = VG_(arena_strdup)(VG_AR_CORE, buf);
         if (!setLocationTy(&(supp->caller[i]), &(supp->caller_ty[i])))
            goto syntax_error;
      }

note that if VG_N_SUPP_CALLERS == 4, then the loop only gets executed a
max of 4 times - meaning a max of 4 lines read. Since the only check for
the "}"-line is inside the loop, if that "}"-line isn't read by the 4th
line, then the parser will fail for that suppressions file.

example:

{
  RuleName
  skin:supp_kind
  fun:foo            i = 0
  fun:bar            i = 1
  fun:baz            i = 2
  fun:func           i = 3; last pass thru the loop.
}                    i = 4; oops. no pass thru the loop. line not
caught.

I guess another fix would be to just read a max of one more line after
the loop to check for the "}" (you wouldn't want to change the for-loop
to accept <= VG_N_SUPP_CALLERS or you could overflow the cllaers array).

Hope my explanation helps,

Jeff

> 
> N
-- 
Jeffrey Stedfast
Evolution Hacker - Ximian, Inc.
fe...@xi...  - www.ximian.com