[PATCH] Push the state, value, and location at the same time.

[Akim Demaille]

This is needed to prepare a forthcoming patch that fuses the three
stacks into one.

        * data/lalr1.cc (parser::yypush_): New.
        (parser::yynewstate): Change the semantics: instead of arriving to
        this label when value and location have been pushed, but yystate
        is to be pushed on the state stack, now the three of them must
        have been pushed before.  yystate still must be the new state.
        This allows to use yypush_ everywhere instead of individual
        handling of the stacks.
---
 ChangeLog     |   14 ++++++++++++++
 data/lalr1.cc |   31 +++++++++++++++++++++----------
 2 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 3b4f3ae..eb12575 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,19 @@
 2008-11-03  Akim Demaille  <address@hidden>
 
+       Push the state, value, and location at the same time.
+       This is needed to prepare a forthcoming patch that fuses the three
+       stacks into one.
+       
+       * data/lalr1.cc (parser::yypush_): New.
+       (parser::yynewstate): Change the semantics: instead of arriving to
+       this label when value and location have been pushed, but yystate
+       is to be pushed on the state stack, now the three of them must
+       have been pushed before.  yystate still must be the new state.
+       This allows to use yypush_ everywhere instead of individual
+       handling of the stacks.
+
+2008-11-03  Akim Demaille  <address@hidden>
+
        Prefer references to pointers.
        * data/lalr1.cc (b4_symbol_actions): New, overrides the default C
        definition to use references instead of pointers.
diff --git a/data/lalr1.cc b/data/lalr1.cc
index 4fabf9f..7195c28 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -407,6 +407,11 @@ b4_error_verbose_if([, int tok])[);
                             semantic_type& yyvalue,
                             location_type& yylocation);
 
+    /// Push a new state on the stack.
+    /// \warning the contents of \a v is stolen.
+    inline void yypush_ (state_type s,
+                         semantic_type& v, const location_type& l);
+
     /// Pop \a n symbols the three stacks.
     inline void yypop_ (unsigned int n = 1);
 
@@ -624,6 +629,15 @@ do {                                       \
   }
 
   void
+  ]b4_parser_class_name[::yypush_ (state_type s,
+                           semantic_type& v, const location_type& l)
+  {
+    yystate_stack_.push (s);
+    yysemantic_stack_.push (v);
+    yylocation_stack_.push (l);
+  }
+
+  void
   ]b4_parser_class_name[::yypop_ (unsigned int n)
   {
     yystate_stack_.pop (n);
@@ -705,12 +719,12 @@ m4_popdef([b4_at_dollar])])dnl
     yystate_stack_ = state_stack_type (0);
     yysemantic_stack_ = semantic_stack_type (0);
     yylocation_stack_ = location_stack_type (0);
-    yysemantic_stack_.push (yylval);
-    yylocation_stack_.push (yylloc);
+    yypush_ (yystate, yylval, yylloc);
 
-    /* New state.  */
+    // A new state was pushed on the stack.
+    // Invariant: yystate == yystack_[0].state, i.e.,
+    // yystate was just pushed onto the state stack.
   yynewstate:
-    yystate_stack_.push (yystate);
     YYCDEBUG << "Entering state " << yystate << std::endl;
 
     /* Accept?  */
@@ -771,8 +785,6 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
 
     /* Discard the token being shifted.  */
     yychar = yyempty_;
-    yysemantic_stack_.push (yylval);
-    yylocation_stack_.push (yylloc);
 
     /* Count tokens shifted since error; after three, turn off error
        status.  */
@@ -780,6 +792,7 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
       --yyerrstatus_;
 
     yystate = yyn;
+    yypush_ (yystate, yylval, yylloc);
     goto yynewstate;
 
   /*-----------------------------------------------------------.
@@ -827,8 +840,6 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
     yypop_ (yylen);
     yylen = 0;
     YY_STACK_PRINT ();
-    yysemantic_stack_.push (yyval);
-    yylocation_stack_.push (yyloc);
 
     /* Shift the result of the reduction.  */
     yyn = yyr1_[yyn];
@@ -838,6 +849,7 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
       yystate = yytable_[yystate];
     else
       yystate = yydefgoto_[yyn - yyntokens_];
+    yypush_ (yystate, yyval, yyloc);
     goto yynewstate;
 
   /*------------------------------------.
@@ -932,14 +944,13 @@ b4_error_verbose_if([, yytoken])[));
     // Using YYLLOC is tempting, but would change the location of
     // the lookahead.  YYLOC is available though.
     YYLLOC_DEFAULT (yyloc, (yyerror_range - 1), 2);
-    yysemantic_stack_.push (yylval);
-    yylocation_stack_.push (yyloc);
 
     /* Shift the error token.  */
     YY_SYMBOL_PRINT ("Shifting", yystos_[yyn],
                     yysemantic_stack_[0], yylocation_stack_[0]);
 
     yystate = yyn;
+    yypush_ (yystate, yylval, yyloc);
     goto yynewstate;
 
     /* Accept.  */
-- 
1.6.0.2.588.g3102