Patch: PR preprocessor/28709

[Tom Tromey <tromey at redhat dot com>]

This patch fixes PR preprocessor/28709.

The bug is a very minor one.  If the user attempts to paste "-" and
">>", cpp will emit a half-pasted "->" token.  The invalid paste is
correctly diagnosed, but the parser emits an error that refers to
"->", which is somewhat confusing.

The problem is that paste_tokens may modify the LHS of the paste
operation.  The patch fixes the bug by making a copy of the LHS while
removing the PASTE_LEFT flag and preserving the old location.  The
actual patch is somewhat involved due to 'const' and a clarification
so that we only use the 'lhs' variable for one purpose.

Bootstrapped and regression tested on x86 FC6.  Test case included.

Ok?

Tom

:ADDPATCH preprocessor:

libcpp
2006-12-29  Tom Tromey  <tromey@redhat.com>

	PR preprocessor/28709:
	* macro.c (paste_tokens): Remove PASTE_LEFT from the old lhs.

gcc/testsuite
2006-12-29  Tom Tromey  <tromey@redhat.com>

	PR preprocessor/28709:
	* gcc.dg/cpp/pr28709.c: New file.

Index: libcpp/macro.c
===================================================================
--- libcpp/macro.c	(revision 120244)
+++ libcpp/macro.c	(working copy)
@@ -431,19 +432,18 @@
 paste_tokens (cpp_reader *pfile, const cpp_token **plhs, const cpp_token *rhs)
 {
   unsigned char *buf, *end, *lhsend;
-  const cpp_token *lhs;
+  cpp_token *lhs;
   unsigned int len;
 
-  lhs = *plhs;
-  len = cpp_token_len (lhs) + cpp_token_len (rhs) + 1;
+  len = cpp_token_len (*plhs) + cpp_token_len (rhs) + 1;
   buf = (unsigned char *) alloca (len);
-  end = lhsend = cpp_spell_token (pfile, lhs, buf, false);
+  end = lhsend = cpp_spell_token (pfile, *plhs, buf, false);
 
   /* Avoid comment headers, since they are still processed in stage 3.
      It is simpler to insert a space here, rather than modifying the
      lexer to ignore comments in some circumstances.  Simply returning
      false doesn't work, since we want to clear the PASTE_LEFT flag.  */
-  if (lhs->type == CPP_DIV && rhs->type != CPP_EQ)
+  if ((*plhs)->type == CPP_DIV && rhs->type != CPP_EQ)
     *end++ = ' ';
   end = cpp_spell_token (pfile, rhs, end, false);
   *end = '\n';
@@ -453,13 +453,22 @@
 
   /* Set pfile->cur_token as required by _cpp_lex_direct.  */
   pfile->cur_token = _cpp_temp_token (pfile);
-  *plhs = _cpp_lex_direct (pfile);
+  lhs = _cpp_lex_direct (pfile);
   if (pfile->buffer->cur != pfile->buffer->rlimit)
     {
+      source_location saved_loc = lhs->src_loc;
+
       _cpp_pop_buffer (pfile);
       _cpp_backup_tokens (pfile, 1);
       *lhsend = '\0';
 
+      /* We have to remove the PASTE_LEFT flag from the old lhs, but
+	 we want to keep the new location.  */
+      *lhs = **plhs;
+      *plhs = lhs;
+      lhs->src_loc = saved_loc;
+      lhs->flags &= ~PASTE_LEFT;
+
       /* Mandatory error for all apart from assembler.  */
       if (CPP_OPTION (pfile, lang) != CLK_ASM)
 	cpp_error (pfile, CPP_DL_ERROR,
@@ -468,6 +477,7 @@
       return false;
     }
 
+  *plhs = lhs;
   _cpp_pop_buffer (pfile);
   return true;
 }

Index: gcc/testsuite/gcc.dg/cpp/pr28709.c
===================================================================
--- gcc/testsuite/gcc.dg/cpp/pr28709.c	(revision 0)
+++ gcc/testsuite/gcc.dg/cpp/pr28709.c	(revision 0)
@@ -0,0 +1,8 @@
+/* Copyright (C) 2006 Free Software Foundation, Inc.  */
+/* PR preprocessor/28709 */
+
+/* { dg-do compile } */
+#define foo - ## >>
+foo;
+/* { dg-error "expected identifier.*'-'" "" { target *-*-* } 6 } */
+/* { dg-error pasting "" { target *-*-* } 6 } */