cpplib: Return endless CPP_EOFs at end of translation unit

[Neil Booth <neil at daikokuya dot demon dot co dot uk>]

With my recent changes to cpplib, it was returning CPP_EOF at the end
of the translation unit, and popping the final buffer at the same
time.  This meant any subsequent calls to cpp_get_token would segfault
since the buffer stack was empty.

Requiring clients to only call cpp_get_token the exact number of times
is a bit onerous, so this patch doesn't pop the final buffer.
fix-header was calling cpp_get_token even after receiving a CPP_EOF,
for example.

I'll bootstrap this on x86 Linux and commit it if it passes.  Gerald,
please confirm this solves your bootstrap issue (and sorry for causing
it).

Neil.

	* cppinit.c (cpp_finish): Pop the final buffer without comment.
	* cpplex.c (_cpp_lex_token): Don't pop the final buffer; and
	take care to avoid multiple no-newline at EOF warnings in that
	case.

Index: cppinit.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cppinit.c,v
retrieving revision 1.168
diff -u -p -r1.168 cppinit.c
--- cppinit.c	2001/08/05 17:31:22	1.168
+++ cppinit.c	2001/08/07 18:28:02
@@ -1010,12 +1010,13 @@ void
 cpp_finish (pfile)
      cpp_reader *pfile;
 {
-  if (CPP_BUFFER (pfile))
-    {
-      cpp_ice (pfile, "buffers still stacked in cpp_finish");
-      while (CPP_BUFFER (pfile))
-	_cpp_pop_buffer (pfile);
-    }
+  /* cpplex.c leaves the final buffer on the stack.  This it so that
+     it returns an unending stream of CPP_EOFs to the client.  If we
+     popped the buffer, we'd derefence a NULL buffer pointer and
+     segfault.  It's nice to allow the client to do worry-free excess
+     cpp_get_token calls.  */
+  while (pfile->buffer)
+    _cpp_pop_buffer (pfile);
 
   /* Don't write the deps file if preprocessing has failed.  */
   if (CPP_OPTION (pfile, print_deps) && pfile->errors == 0)
Index: cpplex.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cpplex.c,v
retrieving revision 1.152
diff -u -p -r1.152 cpplex.c
--- cpplex.c	2001/08/05 17:31:23	1.152
+++ cpplex.c	2001/08/07 18:28:12
@@ -897,21 +897,26 @@ _cpp_lex_token (pfile, result)
 	pfile->line--;
       else if (! pfile->state.parsing_args)
 	{
-	  unsigned char ret = pfile->buffer->return_at_eof;
-
 	  /* Non-empty files should end in a newline.  Don't warn for
 	     command line and _Pragma buffers.  */
 	  if (pfile->lexer_pos.col != 0)
 	    {
-	      /* Account for the missing \n.  */
+	      /* Account for the missing \n, prevent multiple warnings.  */
 	      pfile->line++;
+	      pfile->lexer_pos.col = 0;
 	      if (!buffer->from_stage3)
 		cpp_pedwarn (pfile, "no newline at end of file");
 	    }
+
+	  /* Don't pop the last file.  */
+	  if (buffer->prev)
+	    {
+	      unsigned char stop = buffer->return_at_eof;
 
-	  _cpp_pop_buffer (pfile);
-	  if (pfile->buffer && !ret)
-	    goto next_token;
+	      _cpp_pop_buffer (pfile);
+	      if (!stop)
+		goto next_token;
+	    }
 	}
       result->type = CPP_EOF;
       return;