yysyntax_error: adjust prior fixes for branch-2.5's lalr1.cc.

[Joel E. Denny]

I pushed this to branch-2.5.

>From 3b8378825ea8c3d2cae8c615a9ebf1f679730895 Mon Sep 17 00:00:00 2001
From: Joel E. Denny <address@hidden>
Date: Sun, 7 Nov 2010 16:10:09 -0500
Subject: [PATCH] yysyntax_error: adjust prior fixes for branch-2.5's lalr1.cc.

On master, there is no yychar in lalr1.cc, but there is on
branch-2.5, and the prior cherry-pick of "Fix handling of yychar
manipulation in user semantic actions" wasn't adjusted for that
difference.
* data/lalr1.cc (yy::parser::parse): Translate yychar before
every use of yytoken, and add comments explaining this approach.
* tests/conflicts.at (%error-verbose and consistent errors):
Extend to test yychar manipulation with lalr1.cc.
---
 ChangeLog          |   12 ++++++++++++
 data/lalr1.cc      |   23 ++++++++++++++++++++++-
 tests/conflicts.at |    9 +++++++--
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 0e711e5..1d80e92 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,17 @@
 2010-11-07  Joel E. Denny  <address@hidden>
 
+       yysyntax_error: adjust prior fixes for branch-2.5's lalr1.cc.
+       On master, there is no yychar in lalr1.cc, but there is on
+       branch-2.5, and the prior cherry-pick of "Fix handling of yychar
+       manipulation in user semantic actions" wasn't adjusted for that
+       difference.
+       * data/lalr1.cc (yy::parser::parse): Translate yychar before
+       every use of yytoken, and add comments explaining this approach.
+       * tests/conflicts.at (%error-verbose and consistent errors):
+       Extend to test yychar manipulation with lalr1.cc.
+
+2010-11-07  Joel E. Denny  <address@hidden>
+
        yysyntax_error: fix for consistent error with lookahead.
        * NEWS (2.5): Document.
        * data/yacc.c (yysyntax_error): In a verbose syntax error
diff --git a/data/lalr1.cc b/data/lalr1.cc
index 33ab08e..8c91fb6 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -692,6 +692,17 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
        default:
           break;
       }
+    /* User semantic actions sometimes alter yychar, and that requires
+       that yytoken be updated with the new translation.  We take the
+       approach of translating immediately before every use of yytoken.
+       One alternative is translating here after every semantic action,
+       but that translation would be missed if the semantic action
+       invokes YYABORT, YYACCEPT, or YYERROR immediately after altering
+       yychar.  In the case of YYABORT or YYACCEPT, an incorrect
+       destructor might then be invoked immediately.  In the case of
+       YYERROR, subsequent parser actions might lead to an incorrect
+       destructor call or verbose syntax error message before the
+       lookahead is translated.  */
     YY_SYMBOL_PRINT ("-> $$ =", yyr1_[yyn], &yyval, &yyloc);
 
     yypop_ (yylen);
@@ -715,6 +726,10 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
   | yyerrlab -- here on detecting error |
   `------------------------------------*/
   yyerrlab:
+    /* Make sure we have latest lookahead translation.  See comments at
+       user semantic actions for why this is necessary.  */
+    yytoken = yytranslate_ (yychar);
+
     /* If not already recovering from an error, report this error.  */
     if (!yyerrstatus_)
       {
@@ -826,7 +841,13 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
 
   yyreturn:
     if (yychar != yyempty_)
-      yydestruct_ ("Cleanup: discarding lookahead", yytoken, &yylval, &yylloc);
+      {
+        /* Make sure we have latest lookahead translation.  See comments
+           at user semantic actions for why this is necessary.  */
+        yytoken = yytranslate_ (yychar);
+        yydestruct_ ("Cleanup: discarding lookahead", yytoken, &yylval,
+                     &yylloc);
+      }
 
     /* Do not reclaim the symbols of the rule which action triggered
        this YYABORT or YYACCEPT.  */
diff --git a/tests/conflicts.at b/tests/conflicts.at
index 1d4eb04..f455d1f 100644
--- a/tests/conflicts.at
+++ b/tests/conflicts.at
@@ -161,6 +161,7 @@ AT_SKEL_JAVA_IF([AT_DATA], [AT_DATA_GRAMMAR])([input.y],
 }]], [[
 
 %code {]AT_SKEL_CC_IF([[
+  #include <cassert>
   #include <string>]], [[
   #include <assert.h>
   #include <stdio.h>
@@ -376,7 +377,7 @@ error-reduce:
 ;
 
 consistent-reduction: /*empty*/ {
-  assert (yychar == YYEMPTY);
+  assert (yychar == ]AT_SKEL_CC_IF([[yyempty_]], [[YYEMPTY]])[);
   yylval = 0;
   yychar = 'b';
 } ;
@@ -400,7 +401,11 @@ AT_CONSISTENT_ERRORS_CHECK([[%glr-parser]],
                            [AT_USER_ACTION_GRAMMAR],
                            [AT_USER_ACTION_INPUT],
                            [['b']], [[none]])
-# No C++ or Java test because yychar cannot be manipulated by users.
+AT_CONSISTENT_ERRORS_CHECK([[%language "c++"]],
+                           [AT_USER_ACTION_GRAMMAR],
+                           [AT_USER_ACTION_INPUT],
+                           [['b']], [[none]])
+# No Java test because yychar cannot be manipulated by users.
 
 AT_CONSISTENT_ERRORS_CHECK([[%define lr.default-reductions consistent]],
                            [AT_USER_ACTION_GRAMMAR],
-- 
1.7.0.4