misleading diagnostics in Bison-generated parser trace

[Paul Eggert]

In <http://lists.gnu.org/archive/html/help-bison/2005-07/msg00040.html>
Joel E. Denny writes:

> I also noticed this at the end of the parser trace:

>   Error: popping token $end ()Error: popping nterm tree ()Error: popping
>   token $end ()

> This did not happen with prior versions of bison for this test case.
> This is a wild guess, but does this have something to do with the new
> destructor call on the start symbol?  If so, `Error' is a bit misleading.

Thanks for mentioning this.  Yes, it has something to do with that.
I installed this patch:

2005-08-21  Paul Eggert  <address@hidden>

        * data/glr.c (yyreturn): Use "Cleanup:" rather than "Error:"
        in yydestruct diagnostic, since it might not be an error.
        Problem reported by Joel Denny near end of
        <http://lists.gnu.org/archive/html/help-bison/2005-07/msg00040.html>.
        * data/lalr1.cc (yyerturn): Likewise.
        * data/yacc.c (yyreturn): Likewise.
        * tests/calc.at (_AT_CHECK_CALC_ERROR): Adjust to the above change.

Index: data/glr.c
===================================================================
RCS file: /cvsroot/bison/bison/data/glr.c,v
retrieving revision 1.113
retrieving revision 1.114
diff -p -u -r1.113 -r1.114
--- data/glr.c  22 Aug 2005 01:05:52 -0000      1.113
+++ data/glr.c  22 Aug 2005 02:31:10 -0000      1.114
@@ -2169,7 +2169,7 @@ b4_syncline(address@hidden@], address@hidden@])])dnl
 
  yyreturn:
   if (yytoken != YYEOF && yytoken != YYEMPTY)
-    yydestruct ("Error: discarding lookahead",
+    yydestruct ("Cleanup: discarding lookahead",
                 yytoken, yylvalp]b4_location_if([, yyllocp])[);
 
   /* If the stack is well-formed, pop the stack until it is empty,
@@ -2183,7 +2183,7 @@ b4_syncline(address@hidden@], address@hidden@])])dnl
          {
            yyGLRState *yys = yystates[0];
 ]b4_location_if([[       yystack.yyerror_range[1].yystate.yyloc = yys->yyloc;]]
-)[         yydestruct ("Error: popping",
+)[         yydestruct ("Cleanup: popping",
                        yystos[yys->yylrState],
                        &yys->yysemantics.yysval]b4_location_if([, 
&yys->yyloc])[);
            yystates[0] = yys->yypred;
Index: data/lalr1.cc
===================================================================
RCS file: /cvsroot/bison/bison/data/lalr1.cc,v
retrieving revision 1.92
retrieving revision 1.93
diff -p -u -r1.92 -r1.93
--- data/lalr1.cc       24 Jul 2005 07:24:22 -0000      1.92
+++ data/lalr1.cc       22 Aug 2005 02:31:10 -0000      1.93
@@ -879,11 +879,11 @@ yyabortlab:
 
 yyreturn:
   if (yylooka_ != yyeof_ && yylooka_ != yyempty_)
-    yydestruct_ ("Error: discarding lookahead", yyilooka_, &yylval, &yylloc);
+    yydestruct_ ("Cleanup: discarding lookahead", yyilooka_, &yylval, &yylloc);
 
   while (yystate_stack_.height () != 1)
     {
-      yydestruct_ ("Error: popping",
+      yydestruct_ ("Cleanup: popping",
                   yystos_[yystate_stack_[0]],
                   &yysemantic_stack_[0],
                   &yylocation_stack_[0]);
Index: data/yacc.c
===================================================================
RCS file: /cvsroot/bison/bison/data/yacc.c,v
retrieving revision 1.101
retrieving revision 1.102
diff -p -u -r1.101 -r1.102
--- data/yacc.c 24 Jul 2005 07:24:22 -0000      1.101
+++ data/yacc.c 22 Aug 2005 02:31:10 -0000      1.102
@@ -1383,11 +1383,11 @@ yyexhaustedlab:
 
 yyreturn:
   if (yychar != YYEOF && yychar != YYEMPTY)
-     yydestruct ("Error: discarding lookahead",
+     yydestruct ("Cleanup: discarding lookahead",
                 yytoken, &yylval]b4_location_if([, &yylloc])[);
   while (yyssp != yyss)
     {
-      yydestruct ("Error: popping",
+      yydestruct ("Cleanup: popping",
                  yystos[*yyssp], yyvsp]b4_location_if([, yylsp])[);
       YYPOPSTACK;
     }
Index: tests/calc.at
===================================================================
RCS file: /cvsroot/bison/bison/tests/calc.at,v
retrieving revision 1.76
retrieving revision 1.77
diff -p -u -r1.76 -r1.77
--- tests/calc.at       19 Jul 2005 06:56:44 -0000      1.76
+++ tests/calc.at       22 Aug 2005 02:31:10 -0000      1.77
@@ -405,6 +405,7 @@ sed '/^Starting/d
 /^Reducing/d
 /^Shifting/d
 /^state/d
+/^Cleanup:/d
 /^Error:/d
 /^Next/d
 /^Discarding/d