Re: user destructor for unresolved GLR semantic value

[Paul Eggert]

"Joel E. Denny" <address@hidden> writes:

> This approach is much easier, but it drops some diagnostic messages.  I
> thought trying to invoke YY_SYMBOL_PRINT() would be worthwhile.

Thanks for mentioning this.  However, I'd rather not complicate
all the skeletons for the sake of this GLR-specific problem.

I installed the following patch instead.  It outputs a bit more
information than the patch you proposed, since it mentions which
popped items were unresolved.  Please let me know how it works for you.

2005-08-25  Paul Eggert  <address@hidden>

        * data/glr.c (yydestroyStackItem): New function.
        (yyrecoverSyntaxError, yyreturn): Use it to improve quality of
        debugging information.  Problem reported by Joel E. Denny.

--- data/glr.c  25 Aug 2005 06:11:34 -0000      1.115
+++ data/glr.c  25 Aug 2005 17:57:23 -0000      1.116
@@ -886,6 +886,26 @@ yyuserMerge (int yyn, YYSTYPE* yy0, YYST
 
 ]b4_yydestruct_generate([b4_c_ansi_function_def])[
 
+static void
+yydestroyStackItem (char const *yymsg, yyGLRState *yys)
+{
+  if (yys->yyresolved)
+    yydestruct (yymsg, yystos[yys->yylrState],
+               &yys->yysemantics.yysval]b4_location_if([, &yys->yyloc])[);
+  else
+    {
+#if YYDEBUG
+      if (yydebug)
+       {
+         YYFPRINTF (stderr, "%s unresolved ", yymsg);
+         yysymprint (stderr, yystos[yys->yylrState],
+                     &yys->yysemantics.yysval]b4_location_if([, 
&yys->yyloc])[);
+         YYFPRINTF (stderr, "\n");
+       }
+#endif
+    }
+}
+
 /** Number of symbols composing the right hand side of rule #RULE. */
 static inline int
 yyrhsLength (yyRuleNum yyrule)
@@ -1981,10 +2001,7 @@ yyrecoverSyntaxError (yyGLRStack* yystac
            }
        }
 ]b4_location_if([[      yystack->yyerror_range[1].yystate.yyloc = 
yys->yyloc;]])[
-      if (yys->yyresolved)
-       yydestruct ("Error: popping",
-                   yystos[yys->yylrState],
-                   &yys->yysemantics.yysval]b4_location_if([, &yys->yyloc])[);
+      yydestroyStackItem ("Error: popping", yys);
       yystack->yytops.yystates[0] = yys->yypred;
       yystack->yynextFree -= 1;
       yystack->yyspaceLeft += 1;
@@ -2184,10 +2201,7 @@ b4_syncline(address@hidden@], address@hidden@])])dnl
          {
            yyGLRState *yys = yystates[0];
 ]b4_location_if([[       yystack.yyerror_range[1].yystate.yyloc = yys->yyloc;]]
-)[         if (yys->yyresolved)
-             yydestruct ("Cleanup: popping",
-                         yystos[yys->yylrState],
-                         &yys->yysemantics.yysval]b4_location_if([, 
&yys->yyloc])[);
+)[         yydestroyStackItem ("Cleanup: popping", yys);
            yystates[0] = yys->yypred;
            yystack.yynextFree -= 1;
            yystack.yyspaceLeft += 1;