lalr1.cc: don't discard non-existent lookahead on syntax error.

[bison.git] / data / lalr1.cc

diff --git a/data/lalr1.cc b/data/lalr1.cc
index 2a9316de82cf1720be01c3ff7d9b54be9e864ad6..6174e824edeb507beb4d33f60ae74cbfbd6d7367 100644 (file)
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -29,7 +29,7 @@ m4_define([b4_integral_parser_table_declare],
 ])
 
 # b4_integral_parser_table_define(TABLE-NAME, CONTENT, COMMENT)
-# ---------------------------------------------
+# -------------------------------------------------------------
 # Define "parser::yy<TABLE-NAME>_" which contents is CONTENT.
 m4_define([b4_integral_parser_table_define],
 [  const b4_int_type_for([$2])
@@ -147,6 +147,7 @@ dnl FIXME: This is wrong, we want computed header guards.
 ]b4_percent_code_get([[requires]])[
 
 ]b4_parse_assert_if([#include <cassert>])[
+#include <stdexcept>
 #include <string>
 #include <iostream>
 #include "stack.hh"
@@ -245,6 +246,14 @@ do {                                                            \
     /// \param yylhs     the nonterminal to push on the stack
     state_type yy_lr_goto_state_ (state_type yystate, int yylhs);
 
+    /// Whether the given \c yypact_ value indicates a defaulted state.
+    /// \param yyvalue   the value to check
+    static bool yy_pact_value_is_default_ (int yyvalue);
+
+    /// Whether the given \c yytable_ value indicates a syntax error.
+    /// \param yyvalue   the value to check
+    static bool yy_table_value_is_error_ (int yyvalue);
+
     /// Internal symbol numbers.
     typedef ]b4_int_type_for([b4_translate])[ token_number_type;
     static const ]b4_int_type(b4_pact_ninf, b4_pact_ninf)[ yypact_ninf_;
@@ -312,7 +321,7 @@ do {                                                            \
       /// The state.
       state_type state;
 
-      /// Return the type corresponding to this state.
+      /// The type (corresponding to \a state).
       inline int type_get_ () const;
     };
 
@@ -389,7 +398,7 @@ m4_if(b4_prefix, [yy], [],
 b4_percent_code_get[]dnl
 
 [#ifndef YY_
-# if YYENABLE_NLS
+# if defined YYENABLE_NLS && YYENABLE_NLS
 #  if ENABLE_NLS
 #   include <libintl.h> /* FIXME: INFRINGES ON USER NAME SPACE */
 #   define YY_(msgid) dgettext ("bison-runtime", msgid)
@@ -651,6 +660,18 @@ b4_percent_code_get[]dnl
       return yydefgoto_[yylhs - yyntokens_];
   }
 
+  inline bool
+  ]b4_parser_class_name[::yy_pact_value_is_default_ (int yyvalue)
+  {
+    return yyvalue == yypact_ninf_;
+  }
+
+  inline bool
+  ]b4_parser_class_name[::yy_table_value_is_error_ (int yyvalue)
+  {
+    return yyvalue == yytable_ninf_;
+  }
+
   int
   ]b4_parser_class_name[::parse ()
   {
@@ -709,7 +730,7 @@ m4_popdef([b4_at_dollar])])dnl
 
     /* Try to take a decision without lookahead.  */
     yyn = yypact_[yystack_[0].state];
-    if (yyn == yypact_ninf_)
+    if (yy_pact_value_is_default_ (yyn))
       goto yydefault;
 
     /* Read a lookahead token.  */
@@ -737,7 +758,7 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param)));])[
     yyn = yytable_[yyn];
     if (yyn <= 0)
       {
-       if (yyn == 0 || yyn == yytable_ninf_)
+       if (yy_table_value_is_error_ (yyn))
          goto yyerrlab;
        yyn = -yyn;
        goto yyreduce;
@@ -794,12 +815,21 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param)));])[
 
     // Perform the reduction.
     YY_REDUCE_PRINT (yyn);
-    switch (yyn)
+    try
+    {
+      switch (yyn)
       {
 ]b4_user_actions[
        default:
           break;
       }
+    }
+    catch (const syntax_error& yyexc)
+    {
+      error (]b4_args(b4_locations_if([yyexc.location]),
+                      [[yyexc.what()]])[);
+      YYERROR;
+    }
     YY_SYMBOL_PRINT ("-> $$ =", yylhs);
 ]b4_variant_if([[
     // Destroy the rhs symbols.
@@ -846,7 +876,7 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param)));])[
         /* Return failure if at end of input.  */
         if (yyla.type == yyeof_)
           YYABORT;
-        else
+        else if (!yyempty)
           {
             yy_destroy_ ("Error: discarding", yyla);
             yyempty = true;
@@ -887,7 +917,7 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param)));])[
       for (;;)
         {
           yyn = yypact_[yystack_[0].state];
-          if (yyn != yypact_ninf_)
+          if (!yy_pact_value_is_default_ (yyn))
             {
               yyn += yyterror_;
               if (0 <= yyn && yyn <= yylast_ && yycheck_[yyn] == yyterror_)
@@ -954,7 +984,8 @@ b4_error_verbose_if([state_type yystate, int yytoken],
     if (yypact_ninf_ < yyn && yyn <= yylast_)
       {
        /* Start YYX at -YYN if negative to avoid negative indexes in
-          YYCHECK.  */
+          YYCHECK.  In other words, skip the first -YYN actions for this
+          state because they are default actions.  */
        int yyxbegin = yyn < 0 ? -yyn : 0;
 
        /* Stay within bounds of both yycheck and yytname.  */
@@ -970,7 +1001,8 @@ b4_error_verbose_if([state_type yystate, int yytoken],
         char const *yyarg[YYERROR_VERBOSE_ARGS_MAXIMUM];
         yyarg[yycount++] = yytname_[yytoken];
        for (int yyx = yyxbegin; yyx < yyxend; ++yyx)
-         if (yycheck_[yyx + yyn] == yyx && yyx != yyterror_)
+         if (yycheck_[yyx + yyn] == yyx && yyx != yyterror_
+             && !yy_table_value_is_error_ (yytable_[yyx + yyn]))
           {
             if (yycount == YYERROR_VERBOSE_ARGS_MAXIMUM)
             {