Re: New bug in cpp, bogus macro redefinition warnings

[Zack Weinberg <zack at wolery dot cumb dot org>]

On Wed, Mar 01, 2000 at 11:56:59PM +0000, grahams wrote:
> Zack
> 
> Here's the test case couldn't be similar! no special
> options just gcc -c bug.c will do the trick.
> 
> Create a source file with the following line (note
> the space at the beginning of the line it's very
> important)
> 
> --------------bug.c------------------------
>  #define _LIBC_LIMITS_H_ /* This tells it not to look for another.  */
> -------------------------------------------
> 
> If I remove the leading space(s) before the # it
> doesn't crash.

Aha - that's it.  Normally, y'see, there isn't a space before the
beginning of the buffer, so it stops.

Please try the appended patch.

zw

Index: cpphash.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/cpphash.c,v
retrieving revision 1.43
diff -u -p -r1.43 cpphash.c
--- cpphash.c	2000/03/01 19:12:17	1.43
+++ cpphash.c	2000/03/02 00:22:51
@@ -487,21 +487,28 @@ 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);
+  if (last_token == START)
+    /* Empty macro definition.  */
+    exp = xstrdup ("\r \r ");
+  else
+    {
+      /* 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 */
-  exp[0] = '\r';
-  exp[1] = ' ';
-  exp[len + 1] = '\r';
-  exp[len + 2] = ' ';
-  exp[len + 3] = '\0';
-  memcpy (&exp[2], pfile->token_buffer + start, len - 1);
+      CPP_NUL_TERMINATE (pfile);
+      len = CPP_WRITTEN (pfile) - start + 1;
+      exp = xmalloc (len + 4); /* space for no-concat markers at either end */
+      exp[0] = '\r';
+      exp[1] = ' ';
+      exp[len + 1] = '\r';
+      exp[len + 2] = ' ';
+      exp[len + 3] = '\0';
+      memcpy (&exp[2], pfile->token_buffer + start, len - 1);
+    }
+
   CPP_SET_WRITTEN (pfile, start);
 
   defn = (DEFINITION *) xmalloc (sizeof (DEFINITION));