Have lalr1.cc catch with Paul Eggert's patch to fix the infinite

error recovery loops.  This patch is based on
<http://mail.gnu.org/archive/html/bison-patches/2003-06/msg00000.html>.
Also, augment the similarity between lalr1.cc and yacc.c.
Note: the locations of error recovery rules are not correct yet.
* data/lalr1.cc: Comment changes to augment the similarity between
lalr1.cc and yacc.c.
(YYERROR): Goto to yyerrorlab, not yyerrlab1.
(yyerrlab1): Remove, but where it used to be (now the bottom part of
yyerrlab), when hitting EOF, pop the whole stack here instead of
merely falling thru the default error handling mechanism.
(yyerrorlab): New label, with the old contents of YYERROR,
plus the following change: pop the stack of rhs corresponding
to the production that invoked YYERROR.  That is how Yacc
behaves (required by POSIX).
* tests/calc.at (AT_CHECK_CALC_LALR1_CC): No longer expected to
fail.

diff --git a/ChangeLog b/ChangeLog
index 639bcf277e01bba25d99d3b1ea32dd443d0829f5..2596b4b3819c20276ce82379953c8e9f015d8074 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,24 @@
+2003-08-25  Akim Demaille  <akim@epita.fr>
+
+       Have lalr1.cc catch with Paul Eggert's patch to fix the infinite
+       error recovery loops.  This patch is based on
+       <http://mail.gnu.org/archive/html/bison-patches/2003-06/msg00000.html>.
+       Also, augment the similarity between lalr1.cc and yacc.c.
+       Note: the locations of error recovery rules are not correct yet.
+
+       * data/lalr1.cc: Comment changes to augment the similarity between
+       lalr1.cc and yacc.c.
+       (YYERROR): Goto to yyerrorlab, not yyerrlab1.
+       (yyerrlab1): Remove, but where it used to be (now the bottom part of
+       yyerrlab), when hitting EOF, pop the whole stack here instead of
+       merely falling thru the default error handling mechanism.
+       (yyerrorlab): New label, with the old contents of YYERROR,
+       plus the following change: pop the stack of rhs corresponding
+       to the production that invoked YYERROR.  That is how Yacc
+       behaves (required by POSIX).
+       * tests/calc.at (AT_CHECK_CALC_LALR1_CC): No longer expected to
+       fail.
+
 2003-08-25  Akim Demaille  <akim@epita.fr>
 
        Tune local.at so that people can "autom4te -l autotest calc.at -o

diff --git a/data/lalr1.cc b/data/lalr1.cc
index 1ec45264ae21215f40b1947033a784d3c5f41ba9..1d7b24318d00a96430750ec97153b153ac1ed87b 100644 (file)
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -328,7 +328,7 @@ m4_if(b4_defines_flag, 0, [], [#include @output_header_name@])[
 
 #define YYACCEPT       goto yyacceptlab
 #define YYABORT                goto yyabortlab
-#define YYERROR                goto yyerrlab1
+#define YYERROR                goto yyerrorlab
 
 
 int
@@ -395,6 +395,8 @@ yy::]b4_parser_class_name[::parse ()
 #endif
     }
 
+  /* If the proper action on seeing token YYTOKEN is to reduce or to
+     detect an error, take that action.  */
   n_ += ilooka_;
   if (n_ < 0 || last_ < n_ || check_[n_] != ilooka_)
     goto yydefault;
@@ -439,16 +441,26 @@ yy::]b4_parser_class_name[::parse ()
   state_ = n_;
   goto yynewstate;
 
-  /* Default action.  */
+/*-----------------------------------------------------------.
+| yydefault -- do the default action for the current state.  |
+`-----------------------------------------------------------*/
  yydefault:
   n_ = defact_[state_];
   if (n_ == 0)
     goto yyerrlab;
   goto yyreduce;
 
-  /* Reduce.  */
+/*-----------------------------.
+| yyreduce -- Do a reduction.  |
+`-----------------------------*/
  yyreduce:
   len_ = r2_[n_];
+  /* If LEN_ is nonzero, implement the default value of the action:
+     `$$ = $1'.  Otherwise, use the top of the stack.
+
+     Otherwise, the following line sets YYVAL to garbage.
+     This behavior is undocumented and Bison
+     users should not rely upon it.  */
   if (len_)
     {
       yyval = semantic_stack_[len_ - 1];
@@ -517,7 +529,9 @@ b4_syncline([@oline@], [@ofile@])[
     state_ = defgoto_[n_ - ntokens_];
   goto yynewstate;
 
-  /* Report and recover from errors.  This is very incomplete.  */
+/*------------------------------------.
+| yyerrlab -- here on detecting error |
+`------------------------------------*/
  yyerrlab:
   /* If not already recovering from an error, report this error.  */
   if (!errstatus)
@@ -558,32 +572,61 @@ b4_syncline([@oline@], [@ofile@])[
        message = "syntax error";
       error_ ();
     }
-  goto yyerrlab1;
-
 
-  /*----------------------------------------------------.
-  | yyerrlab1 -- error raised explicitly by an action.  |
-  `----------------------------------------------------*/
- yyerrlab1:
   if (errstatus == 3)
     {
       /* If just tried and failed to reuse lookahead token after an
         error, discard it.  */
 
       /* Return failure if at end of input.  */
-      if (looka_ == eof_)
-       goto yyabortlab;
+      if (looka_ <= eof_)
+        {
+          /* If at end of input, pop the error token,
+            then the rest of the stack, then return failure.  */
+         if (looka_ == eof_)
+            for (;;)
+              {
+                 state_stack_.pop ();
+                 semantic_stack_.pop ();
+                 location_stack_.pop ();
+                if (state_stack_.height () == 1)
+                  YYABORT;
+//              YYDSYMPRINTF ("Error: popping", yystos[*yyssp], yyvsp, yylsp);
+// FIXME: yydestruct (yystos[*yyssp], yyvsp]b4_location_if([, yylsp])[);
+              }
+        }
+      else
+        {
 #if YYDEBUG
-      YYCDEBUG << "Discarding token " << looka_
-              << " (" << name_[ilooka_] << ")." << std::endl;
+           YYCDEBUG << "Discarding token " << looka_
+                   << " (" << name_[ilooka_] << ")." << std::endl;
+//       yydestruct (yytoken, &yylval]b4_location_if([, &yylloc])[);
 #endif
-      looka_ = empty_;
+           looka_ = empty_;
+        }
     }
 
   /* Else will try to reuse lookahead token after shifting the error
      token.  */
+  goto yyerrlab1;
+
+
+/*---------------------------------------------------.
+| yyerrorlab -- error raised explicitly by YYERROR.  |
+`---------------------------------------------------*/
+yyerrorlab:
+
+  state_stack_.pop (len_);
+  semantic_stack_.pop (len_);
+  location_stack_.pop (len_);
+  state_ = state_stack_[0];
+  goto yyerrlab1;
 
-  errstatus = 3;
+/*-------------------------------------------------------------.
+| yyerrlab1 -- common code for both syntax error and YYERROR.  |
+`-------------------------------------------------------------*/
+yyerrlab1:
+  errstatus = 3;       /* Each real token shifted decrements this.  */
 
   for (;;)
     {
@@ -601,7 +644,7 @@ b4_syncline([@oline@], [@ofile@])[
 
       /* Pop the current state because it cannot handle the error token.  */
       if (state_stack_.height () == 1)
-       goto yyabortlab;
+       YYABORT;
 
 #if YYDEBUG
       if (debug_)
@@ -625,9 +668,10 @@ b4_syncline([@oline@], [@ofile@])[
        }
 #endif
 
-      state_ = (state_stack_.pop (), state_stack_[0]);
+      state_stack_.pop ();
       semantic_stack_.pop ();
-      location_stack_.pop ();;
+      location_stack_.pop ();
+      state_ = state_stack_[0];
 
 #if YYDEBUG
       if (debug_)

diff --git a/tests/calc.at b/tests/calc.at
index 8c68dfd746183427565c402e494cdce5e98d3135..26dcf8600093185e687d6834a834b821bab7c781 100644 (file)
--- a/tests/calc.at
+++ b/tests/calc.at
@@ -611,7 +611,7 @@ AT_BANNER([[Simple LALR1 C++ Calculator.]])
 # Start a testing chunk which compiles `calc' grammar with
 # the C++ skeleton, and performs several tests over the parser.
 m4_define([AT_CHECK_CALC_LALR1_CC],
-[AT_CHECK_CALC([%skeleton "lalr1.cc"] $@, [expected to fail])])
+[AT_CHECK_CALC([%skeleton "lalr1.cc"] $@)])
 
 # AT_CHECK_CALC_LALR1_CC()