preprocessor/6521: -MG creates dependency with wrong path

[Robert Spier]

>> Why is this the intended behavior?  It doesn't make much sense to me.
>
>It's intended because it's what the comment in the code says and
>does.

Ok.. But why?   Beyond it's existence, it doesn't make any sense to
me.

>I'd welcome a patch to do something more sensible.  You can wait for me
>to look at it, but it's pretty near the bottom of my to-do list.

The only sensible patch I can think of is to remove this odd
functionality entirely.

The below patch unifies handling for system and non-system include
files and removes the special case.  It only affects -MG, and brings
it in line with the documentation:

      -MG When used with -M or -MM, -MG says to treat missing
           header files as generated files and assume they live
           in the same directory as the source file.  It sup­
           presses preprocessed output, as a missing header file
           is ordinarily an error.

The patch is against the 20020506 snapshot.  

Thanks!

-R

===================================================================
RCS file: gcc/cppfiles.c,v
retrieving revision 1.1
diff -u -r1.1 gcc/cppfiles.c
--- gcc/cppfiles.c      2002-05-07 22:33:13-07  1.1
+++ gcc/cppfiles.c      2002-05-07 22:35:48-07
@@ -658,28 +658,8 @@
 
   if (CPP_OPTION (pfile, print_deps_missing_files) && print_dep)
     {
-      if (!angle_brackets || IS_ABSOLUTE_PATHNAME (fname))
+      /* Assume missing headers are in the current directory */
        deps_add_dep (pfile->deps, fname);
-      else
-       {
-         /* If requested as a system header, assume it belongs in
-            the first system header directory.  */
-         struct search_path *ptr = CPP_OPTION (pfile, bracket_include);
-         char *p;
-         int len = 0, fname_len = strlen (fname);
-
-         if (ptr)
-           len = ptr->len;
-
-         p = (char *) alloca (len + fname_len + 2);
-         if (len)
-           {
-             memcpy (p, ptr->name, len);
-             p[len++] = '/';
-           }
-         memcpy (p + len, fname, fname_len + 1);
-         deps_add_dep (pfile->deps, p);
-       }
     }
   /* If -M was specified, then don't count this as an error, because
      we can still produce correct output.  Otherwise, we can't produce