Re: New bug in cpp, bogus macro redefinition warnings

[grahams <grahams at rcp dot co dot uk>]

Zack

With this patch applied I get a SIGSEG in cpp when
compile libgcc.

The problem was the call to memcpy(&exp[2], .., len-1)
which is a few lines after your patch was being 
called with -1 a negative count!  (i.e. len was 0)

I think you probably need a "&& here > start"
as well as the "here > last".

I'll try and dig up a test case which triggers the
problem.

Graham



Zack Weinberg wrote:
> 
> On Wed, Mar 01, 2000 at 09:37:34AM -0800, Zack Weinberg wrote:
> > On Wed, Mar 01, 2000 at 11:24:37AM -0500, Kaveh R. Ghazi wrote:
> > > Bootstrapping last night's snapshot on sparc-sun-solaris2.7 exposed a
> > > new bug in cpp.  I get large amounts of macro redefinition warnings
> > > (~1200) from the system headers.
> > >
> > > They come from macros defined to the same value more than once, but
> > > one instance is followed by a comment.  E.g. you can see what I mean
> > > in the following two line file.
> > >
> > >  > #define FOO 10 /* sdf */
> > >  > #define FOO 10
> > >
> > > (Perhaps you want to install this as a test case.)
> > >
> > > With last night's "gcc version 2.96 20000229 (experimental)", it gives:
> > >
> > >  > foo.c:2:14: warning: `FOO' redefined
> > >  > foo.c:1:11: warning: this is the location of the previous definition
> >
> > Aaargh.  Yes, I see the problem.  Please try this patch - will commit,
> > with test case, once it completes bootstrap.
> 
> That wasn't quite the right patch.
> 
> I have committed this, which should fix the bug.
> 
> zw
> 
>         * cpphash.c (collect_expansion): Trim trailing white space
>         from macro definitions, but don't go past the last insertion
>         point.
>         * gcc.dg/cpp-redef.c: New test.
> ===================================================================
> Index: cpphash.c
> --- cpphash.c   2000/03/01 00:57:08     1.42
> +++ cpphash.c   2000/03/01 19:10:01
> @@ -487,6 +487,12 @@ collect_expansion (pfile, arglist)
>    else if (last_token == PASTE)
>      cpp_error (pfile, "`##' at end of macro definition");
> 
> +  /* Trim trailing white space from definition.  */
> +  here = CPP_WRITTEN (pfile);
> +  while (here > last && is_hspace (pfile->token_buffer [here-1]))
> +    here--;
> +  CPP_SET_WRITTEN (pfile, here);
> +
>    CPP_NUL_TERMINATE (pfile);
>    len = CPP_WRITTEN (pfile) - start + 1;
>    exp = xmalloc (len + 4); /* space for no-concat markers at either end */
> ===================================================================