proposed patch to data/yacc.c to fix the "unused label" warning

[Paul Eggert]

We seem to have continuing problems with people reporting "unused
label" warnings for yyerrlab1, due to my 2002-12-27 yacc.c bugfix.
Here's a proposed patch to fix this.

2003-01-17  Paul Eggert  <address@hidden>

        * data/yacc.c (YYERROR): Move code from yyerrlab1 to here, so that
        we don't need to worry about yyerrlab1 being reported as an
        "unused label" by non-GCC C compilers.  The downside is that if
        locations are used then a couple of statements are duplicated each
        time YYERROR is invoked, but the upside is that the warnings
        should vanish.
        (yyerrlab1): Move code to YERROR.
        (yyerrlab2): Remove.  Change uses back to yyerrlab1.
        This reverts some of the 2002-12-27 change.

--- yacc.c.~1.50.~      2003-01-04 16:31:06.000000000 -0800
+++ yacc.c      2003-01-17 01:10:30.700840000 -0800
@@ -465,7 +465,15 @@ static const ]b4_int_type_for([b4_stos])
 
 #define YYACCEPT       goto yyacceptlab
 #define YYABORT                goto yyabortlab
-#define YYERROR                goto yyerrlab1
+#define YYERROR                ]b4_location_if([do                             
\
+                         {                             \
+                           yylerrsp = yylsp;           \
+                           *++yylerrsp = yyloc;        \
+                           goto yyerrlab1;             \
+                         }                             \
+                       while (0)],
+                       [goto yyerrlab1])[
+
 
 /* Like YYERROR except do call yyerror.  This remains here temporarily
    to ease the transition to the new meaning of YYERROR, for GCC.
@@ -1103,33 +1111,13 @@ yyerrlab:
 
   /* Else will try to reuse lookahead token after shifting the error
      token.  */
-  goto yyerrlab2;
+  goto yyerrlab1;
 
 
 /*----------------------------------------------------.
 | yyerrlab1 -- error raised explicitly by an action.  |
 `----------------------------------------------------*/
 yyerrlab1:
-
-  /* Suppress GCC warning that yyerrlab1 is unused when no action
-     invokes YYERROR.  MacOS 10.2.3's buggy "smart preprocessor"
-     insists on the trailing semicolon.  */
-#if defined (__GNUC_MINOR__) && 2093 <= (__GNUC__ * 1000 + __GNUC_MINOR__)
-  /* GNU C++ (as of version 3.2.1) does not allow attributes on labels.  */
-# ifndef __cplusplus
-  __attribute__ ((__unused__));
-# endif
-#endif
-
-]b4_location_if([  yylerrsp = yylsp;
-  *++yylerrsp = yyloc;])[
-  goto yyerrlab2;
-
-
-/*---------------------------------------------------------------.
-| yyerrlab2 -- pop states until the error token can be shifted.  |
-`---------------------------------------------------------------*/
-yyerrlab2:
   yyerrstatus = 3;     /* Each real token shifted decrements this.  */
 
   for (;;)