Warn about dubious constructions like "%token T T".

* src/symtab.h (struct symbol.declared): New member.
* src/symtab.c (symbol_new): Initialize it to false.
(symbol_class_set): New arg DECLARING, specifying whether
this is a declaration that we want to warn about, if there
is more than one of them.  All uses changed.

ChangeLog

@@ -1,5 +1,13 @@
 2006-01-03  Paul Eggert  <eggert@cs.ucla.edu>
 
+	Warn about dubious constructions like "%token T T".
+	Reported by twlevo.
+	* src/symtab.h (struct symbol.declared): New member.
+	* src/symtab.c (symbol_new): Initialize it to false.
+	(symbol_class_set): New arg DECLARING, specifying whether
+	this is a declaration that we want to warn about, if there
+	is more than one of them.  All uses changed.
+
 	* data/glr.c, data/glr.cc, data/lalr1.cc, data/yacc.c:
 	Allow multiple %union directives, whose contents concatenate.
 	* src/parse-gram.y (grammar_declaration): Likewise.

src/parse-gram.y

@@ -1,6 +1,6 @@
 %{/* Bison Grammar Parser                             -*- C -*-
 
-   Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -346,24 +346,24 @@ symbol_def:
      }
 | ID
      {
-       symbol_class_set ($1, current_class, @1);
+       symbol_class_set ($1, current_class, @1, true);
        symbol_type_set ($1, current_type, @1);
      }
 | ID INT
     {
-      symbol_class_set ($1, current_class, @1);
+      symbol_class_set ($1, current_class, @1, true);
       symbol_type_set ($1, current_type, @1);
       symbol_user_token_number_set ($1, $2, @2);
     }
 | ID string_as_id
     {
-      symbol_class_set ($1, current_class, @1);
+      symbol_class_set ($1, current_class, @1, true);
       symbol_type_set ($1, current_type, @1);
       symbol_make_alias ($1, $2, @$);
     }
 | ID INT string_as_id
     {
-      symbol_class_set ($1, current_class, @1);
+      symbol_class_set ($1, current_class, @1, true);
       symbol_type_set ($1, current_type, @1);
       symbol_user_token_number_set ($1, $2, @2);
       symbol_make_alias ($1, $3, @$);
@@ -441,7 +441,7 @@ string_as_id:
   STRING
     {
       $$ = symbol_get (quotearg_style (c_quoting_style, $1), @1);
-      symbol_class_set ($$, token_sym, @1);
+      symbol_class_set ($$, token_sym, @1, false);
     }
 ;
 

src/scan-gram.l

@@ -1,6 +1,6 @@
 /* Bison Grammar Scanner                             -*- C -*-
 
-   Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -420,7 +420,7 @@ splice	 (\\[ \f\t\v]*\n)*
     val->symbol = symbol_get (quotearg_style (escape_quoting_style,
 					      last_string),
 			      *loc);
-    symbol_class_set (val->symbol, token_sym, *loc);
+    symbol_class_set (val->symbol, token_sym, *loc, false);
     last_string_1 = last_string[1];
     symbol_user_token_number_set (val->symbol, last_string_1, *loc);
     STRING_FREE;

src/symtab.c

@@ -1,7 +1,7 @@
 /* Symbol table manager for Bison.
 
-   Copyright (C) 1984, 1989, 2000, 2001, 2002, 2004, 2005 Free Software
+   Copyright (C) 1984, 1989, 2000, 2001, 2002, 2004, 2005, 2006 Free
-   Foundation, Inc.
+   Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -65,6 +65,7 @@ symbol_new (uniqstr tag, location loc)
 
   res->alias = NULL;
   res->class = unknown_sym;
+  res->declared = false;
 
   if (nsyms == SYMBOL_NUMBER_MAXIMUM)
     fatal (_("too many symbols in input grammar (limit is %d)"),
@@ -182,7 +183,7 @@ symbol_precedence_set (symbol *sym, int prec, assoc a, location loc)
     }
 
   /* Only terminals have a precedence. */
-  symbol_class_set (sym, token_sym, loc);
+  symbol_class_set (sym, token_sym, loc, false);
 }
 
 
@@ -191,10 +192,13 @@ symbol_precedence_set (symbol *sym, int prec, assoc a, location loc)
 `------------------------------------*/
 
 void
-symbol_class_set (symbol *sym, symbol_class class, location loc)
+symbol_class_set (symbol *sym, symbol_class class, location loc, bool declaring)
 {
   if (sym->class != unknown_sym && sym->class != class)
-    complain_at (loc, _("symbol %s redefined"), sym->tag);
+    {
+      complain_at (loc, _("symbol %s redefined"), sym->tag);
+      sym->declared = false;
+    }
 
   if (class == nterm_sym && sym->class != nterm_sym)
     sym->number = nvars++;
@@ -202,6 +206,13 @@ symbol_class_set (symbol *sym, symbol_class class, location loc)
     sym->number = ntokens++;
 
   sym->class = class;
+
+  if (declaring)
+    {
+      if (sym->declared)
+	warn_at (loc, _("symbol %s redeclared"), sym->tag);
+      sym->declared = true;
+    }
 }
 
 

src/symtab.h

@@ -1,6 +1,6 @@
 /* Definitions for symtab.c and callers, part of Bison.
 
-   Copyright (C) 1984, 1989, 1992, 2000, 2001, 2002, 2004, 2005
+   Copyright (C) 1984, 1989, 1992, 2000, 2001, 2002, 2004, 2005, 2006
    Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
@@ -79,6 +79,7 @@ struct symbol
      identifier-symbol pair for an alias.  */
   symbol *alias;
   symbol_class class;
+  bool declared;
 };
 
 /* Undefined user number.  */
@@ -121,7 +122,8 @@ void symbol_printer_set (symbol *sym, const char *printer, location loc);
 void symbol_precedence_set (symbol *sym, int prec, assoc a, location loc);
 
 /* Set the CLASS associated with SYM.  */
-void symbol_class_set (symbol *sym, symbol_class class, location loc);
+void symbol_class_set (symbol *sym, symbol_class class, location loc,
+		       bool declaring);
 
 /* Set the USER_TOKEN_NUMBER associated with SYM.  */
 void symbol_user_token_number_set (symbol *sym, int user_number, location loc);