FYI: fix %start after first rule

[Joel E. Denny]

I've just noticed that I'm not being so consistent with how I choose where 
to add test cases.  Should all bugs be demonstrated in regression.at?  Or 
is it better to be more specific when another set, like input.at, makes 
sense?

Joel

Index: ChangeLog
===================================================================
RCS file: /sources/bison/bison/ChangeLog,v
retrieving revision 1.1552
diff -p -u -r1.1552 ChangeLog
--- ChangeLog   18 Aug 2006 21:43:18 -0000      1.1552
+++ ChangeLog   20 Aug 2006 03:07:49 -0000
@@ -1,3 +1,15 @@
+2006-08-19  Joel E. Denny  <address@hidden>
+
+       Allow %start after the first rule.
+       * src/reader.c (grammar_current_rule_begin): Don't set the start symbol
+       when parsing the first rule.
+       (check_and_convert_grammar): Search for it here after all grammar
+       declarations have been parsed.  Skip midrules, which have dummy LHS
+       nonterminals.
+       * src/symtab.c (symbol_is_dummy): New function.
+       * src/symtab.h (symbol_is_dummy): Declare it.
+       * tests/input.at (%start after first rule): New test.
+
 2006-08-18  Joel E. Denny  <address@hidden>
 
        Redo some of the previous commit: add back the ability to use
Index: src/reader.c
===================================================================
RCS file: /sources/bison/bison/src/reader.c,v
retrieving revision 1.269
diff -p -u -r1.269 reader.c
--- src/reader.c        18 Aug 2006 21:43:18 -0000      1.269
+++ src/reader.c        20 Aug 2006 03:07:49 -0000
@@ -225,13 +225,6 @@ static symbol_list *previous_rule_end = 
 void
 grammar_current_rule_begin (symbol *lhs, location loc)
 {
-  if (!start_flag)
-    {
-      startsymbol = lhs;
-      startsymbol_location = loc;
-      start_flag = true;
-    }
-
   /* Start a new rule and record its lhs.  */
   ++nrules;
   previous_rule_end = grammar_end;
@@ -607,6 +600,23 @@ check_and_convert_grammar (void)
       endtoken->user_token_number = 0;
     }
 
+  /* Find the start symbol if no %start.  */
+  if (!start_flag)
+    {
+      symbol_list *node;
+      for (node = grammar;
+           node != NULL && symbol_is_dummy (node->sym);
+           node = node->next)
+        {
+          for (node = node->next;
+               node != NULL && node->sym != NULL;
+               node = node->next)
+            ;
+        }
+      assert (node != NULL);
+      grammar_start_symbol_set (node->sym, node->sym->location);
+    }
+
   /* Insert the initial rule, whose line is that of the first rule
      (not that of the start symbol):
 
Index: src/symtab.c
===================================================================
RCS file: /sources/bison/bison/src/symtab.c,v
retrieving revision 1.77
diff -p -u -r1.77 symtab.c
--- src/symtab.c        18 Aug 2006 21:43:18 -0000      1.77
+++ src/symtab.c        20 Aug 2006 03:07:49 -0000
@@ -615,6 +615,11 @@ dummy_symbol_get (location loc)
   return sym;
 }
 
+bool
+symbol_is_dummy (const symbol *sym)
+{
+  return sym->tag[0] == '@';
+}
 
 /*-------------------.
 | Free the symbols.  |
Index: src/symtab.h
===================================================================
RCS file: /sources/bison/bison/src/symtab.h,v
retrieving revision 1.63
diff -p -u -r1.63 symtab.h
--- src/symtab.h        29 Jul 2006 05:53:41 -0000      1.63
+++ src/symtab.h        20 Aug 2006 03:07:49 -0000
@@ -133,6 +133,9 @@ symbol *symbol_get (const char *key, loc
    Its name cannot conflict with the user's names.  */
 symbol *dummy_symbol_get (location loc);
 
+/** Is this a dummy nonterminal?  */
+bool symbol_is_dummy (const symbol *sym);
+
 /** Declare the new symbol \c sym.  Make it an alias of \c symval.  */
 void symbol_make_alias (symbol *sym, symbol *symval, location loc);
 
Index: tests/input.at
===================================================================
RCS file: /sources/bison/bison/tests/input.at,v
retrieving revision 1.53
diff -p -u -r1.53 input.at
--- tests/input.at      14 Aug 2006 20:51:33 -0000      1.53
+++ tests/input.at      20 Aug 2006 03:07:49 -0000
@@ -537,3 +537,24 @@ input.y:20.1: syntax error, unexpected e
 ]])
 
 AT_CLEANUP
+
+
+## ------------------------- ##
+## %start after first rule.  ##
+## ------------------------- ##
+
+AT_SETUP([%start after first rule])
+
+# Bison once complained that a %start after the first rule was a redeclaration
+# of the start symbol.
+
+AT_DATA([input.y],
+[[%%
+false_start: ;
+start: false_start ;
+%start start;
+]])
+
+AT_CHECK([bison -o input.c input.y])
+
+AT_CLEANUP