* tests/glr-regression.at (Uninitialized location when reporting

ambiguity): New test case.
* data/glr.c (yyresolveLocations): New function, which uses
YYLLOC_DEFAULT.
(yyresolveValue): Invoke yyresolveLocations before reporting an
ambiguity.
* doc/bison.texinfo (Default Action for Locations): Note
YYLLOC_DEFAULT's usage for ambiguity locations.
(GLR Semantic Actions): Cross-reference those notes.

diff --git a/ChangeLog b/ChangeLog
index 1dce255377e1f3c3b3036f67f759084b6733638f..ecd42da63b34b55a0af802b56806595b01065466 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2006-03-06  Joel E. Denny  <jdenny@ces.clemson.edu>
+
+       * tests/glr-regression.at (Uninitialized location when reporting
+       ambiguity): New test case.
+       * data/glr.c (yyresolveLocations): New function, which uses
+       YYLLOC_DEFAULT.
+       (yyresolveValue): Invoke yyresolveLocations before reporting an
+       ambiguity.
+       * doc/bison.texinfo (Default Action for Locations): Note
+       YYLLOC_DEFAULT's usage for ambiguity locations.
+       (GLR Semantic Actions): Cross-reference those notes.
+

 2006-03-04  Joel E. Denny  <jdenny@ces.clemson.edu>
 
        * tests/glr-regression.at (Leaked semantic values when reporting
 2006-03-04  Joel E. Denny  <jdenny@ces.clemson.edu>
 
        * tests/glr-regression.at (Leaked semantic values when reporting

diff --git a/data/glr.c b/data/glr.c
index 13fd2ff2872c4914aaa9aecd97ad67841fdf47e8..a810bcdc4e0f9e036f8df48236f453a98078f945 100644 (file)
--- a/data/glr.c
+++ b/data/glr.c
@@ -1803,6 +1803,57 @@ yyreportAmbiguity (yySemanticOption* yyx0,
   return yyabort;
 }
 
   return yyabort;
 }
 

+/** Starting at and including state S, resolve the location for each of the
+ *  previous N states that is unresolved.  The first semantic option of a state
+ *  is always chosen.  */
+static void
+yyresolveLocations (yyGLRState* yys, int yyn,
+                   yyGLRStack *yystackp]b4_user_formals[)
+{
+  if (0 < yyn)
+    {
+      yyresolveLocations (yys->yypred, yyn-1, yystackp]b4_user_args[);
+      if (!yys->yyresolved)
+       {
+         yySemanticOption *yyoption;
+         yyGLRStackItem yyrhs[1 + YYMAXRHS];
+         int yynrhs;
+         int yychar_current;
+         YYSTYPE yylval_current;
+         YYLTYPE yylloc_current;
+         yyoption = yys->yysemantics.yyfirstVal;
+         YYASSERT (yyoption != NULL);
+         yynrhs = yyrhsLength (yyoption->yyrule);
+         if (yynrhs > 0)
+           {
+             yyGLRState *yys;
+             int yyi;
+             yyresolveLocations (yyoption->yystate, yynrhs,
+                                 yystackp]b4_user_args[);
+             for (yys = yyoption->yystate, yyi = yynrhs;
+                  yyi >= 1;
+                  yys = yys->yypred, yyi -= 1)
+               yyrhs[yyi].yystate.yyloc = yys->yyloc;
+           }
+         else
+           {
+             yyGLRState *yyprevious = yyoption->yystate;
+             YYASSERT (yyprevious->yyresolved);
+             yyrhs[0].yystate.yyloc = yyprevious->yyloc;
+           }
+         yychar_current = yychar;
+         yylval_current = yylval;
+         yylloc_current = yylloc;
+         yychar = yyoption->yyrawchar;
+         yylval = yyoption->yyval;
+         yylloc = yyoption->yyloc;
+         YYLLOC_DEFAULT ((yys->yyloc), yyrhs, yynrhs);
+         yychar = yychar_current;
+         yylval = yylval_current;
+         yylloc = yylloc_current;
+       }
+    }
+}

 
 /** Resolve the ambiguity represented in state S, perform the indicated
  *  actions, and set the semantic value of S.  If result != yyok, the chain of
 
 /** Resolve the ambiguity represented in state S, perform the indicated
  *  actions, and set the semantic value of S.  If result != yyok, the chain of


@@ -1837,6 +1888,7 @@ yyresolveValue (yyGLRState* yys, yyGLRStack* yystackp]b4_user_formals[)
          switch (yypreference (yybest, yyp))
            {
            case 0:
          switch (yypreference (yybest, yyp))
            {
            case 0:

+             yyresolveLocations (yys, 1, yystackp]b4_user_args[);

              return yyreportAmbiguity (yybest, yyp]b4_pure_args[);
              break;
            case 1:
              return yyreportAmbiguity (yybest, yyp]b4_pure_args[);
              break;
            case 1:

diff --git a/doc/bison.texinfo b/doc/bison.texinfo
index eb36845f3499eb5b538c9ccff10c63d4bf5c1fbb..27d2bd4a89130d3674e8c145b1c2c891a8b25ebd 100644 (file)
--- a/doc/bison.texinfo
+++ b/doc/bison.texinfo
@@ -1135,13 +1135,16 @@ memory referenced by @code{yylval}.
 @findex YYERROR
 @cindex @acronym{GLR} parsers and @code{YYERROR}
 Another Bison feature requiring special consideration is @code{YYERROR}
 @findex YYERROR
 @cindex @acronym{GLR} parsers and @code{YYERROR}
 Another Bison feature requiring special consideration is @code{YYERROR}

-(@pxref{Action Features}), which you can invoke in any semantic action to
+(@pxref{Action Features}), which you can invoke in a semantic action to

 initiate error recovery.
 During deterministic @acronym{GLR} operation, the effect of @code{YYERROR} is
 the same as its effect in an @acronym{LALR}(1) parser.
 In a deferred semantic action, its effect is undefined.
 @c The effect is probably a syntax error at the split point.
 
 initiate error recovery.
 During deterministic @acronym{GLR} operation, the effect of @code{YYERROR} is
 the same as its effect in an @acronym{LALR}(1) parser.
 In a deferred semantic action, its effect is undefined.
 @c The effect is probably a syntax error at the split point.
 

+Also, see @ref{Location Default Action, ,Default Action for Locations}, which
+describes a special usage of @code{YYLLOC_DEFAULT} in @acronym{GLR} parsers.
+

 @node Compiler Requirements
 @subsection Considerations when Compiling @acronym{GLR} Parsers
 @cindex @code{inline}
 @node Compiler Requirements
 @subsection Considerations when Compiling @acronym{GLR} Parsers
 @cindex @code{inline}


@@ -3571,6 +3574,7 @@ This location is stored in @code{yylloc}.
 @node Location Default Action
 @subsection Default Action for Locations
 @vindex YYLLOC_DEFAULT
 @node Location Default Action
 @subsection Default Action for Locations
 @vindex YYLLOC_DEFAULT

+@cindex @acronym{GLR} parsers and @code{YYLLOC_DEFAULT}

 
 Actually, actions are not the best place to compute locations.  Since
 locations are much more general than semantic values, there is room in
 
 Actually, actions are not the best place to compute locations.  Since
 locations are much more general than semantic values, there is room in


@@ -3578,6 +3582,9 @@ the output parser to redefine the default action to take for each
 rule.  The @code{YYLLOC_DEFAULT} macro is invoked each time a rule is
 matched, before the associated action is run.  It is also invoked
 while processing a syntax error, to compute the error's location.
 rule.  The @code{YYLLOC_DEFAULT} macro is invoked each time a rule is
 matched, before the associated action is run.  It is also invoked
 while processing a syntax error, to compute the error's location.

+Before reporting an unresolvable syntactic ambiguity, a @acronym{GLR}
+parser invokes @code{YYLLOC_DEFAULT} recursively to compute the location
+of that ambiguity.

 
 Most of the time, this macro is general enough to suppress location
 dedicated code from semantic actions.
 
 Most of the time, this macro is general enough to suppress location
 dedicated code from semantic actions.


@@ -3586,9 +3593,11 @@ The @code{YYLLOC_DEFAULT} macro takes three parameters.  The first one is
 the location of the grouping (the result of the computation).  When a
 rule is matched, the second parameter identifies locations of
 all right hand side elements of the rule being matched, and the third
 the location of the grouping (the result of the computation).  When a
 rule is matched, the second parameter identifies locations of
 all right hand side elements of the rule being matched, and the third

-parameter is the size of the rule's right hand side.  When processing
-a syntax error, the second parameter identifies locations of
-the symbols that were discarded during error processing, and the third
+parameter is the size of the rule's right hand side.
+When a @acronym{GLR} parser reports an ambiguity, which of multiple candidate
+right hand sides it passes to @code{YYLLOC_DEFAULT} is undefined.
+When processing a syntax error, the second parameter identifies locations
+of the symbols that were discarded during error processing, and the third

 parameter is the number of discarded symbols.
 
 By default, @code{YYLLOC_DEFAULT} is defined this way:
 parameter is the number of discarded symbols.
 
 By default, @code{YYLLOC_DEFAULT} is defined this way:

diff --git a/tests/glr-regression.at b/tests/glr-regression.at
index c9b745bc36706207a2692c80231e917c30247886..a36de9e27d31008320a53ab042bc4908695ded95 100644 (file)
--- a/tests/glr-regression.at
+++ b/tests/glr-regression.at
@@ -1576,3 +1576,82 @@ AT_CHECK([[./glr-regr16]], 0, [],
 ])
 
 AT_CLEANUP
 ])
 
 AT_CLEANUP

+
+
+## ------------------------------------------------------------------------- ##
+## Uninitialized location when reporting ambiguity.                         ##
+## ------------------------------------------------------------------------- ##
+
+AT_SETUP([Uninitialized location when reporting ambiguity])
+AT_DATA_GRAMMAR([glr-regr17.y],
+[[
+%glr-parser
+%locations
+%pure-parser
+%error-verbose
+
+%union { int dummy; }
+
+%{
+  static void yyerror (YYLTYPE *, char const *);
+  static int yylex (YYSTYPE *, YYLTYPE *);
+%}
+
+%initial-action {
+  @$.first_line = 1;
+  @$.first_column = 1;
+  @$.last_line = 1;
+  @$.last_column = 1;
+}
+
+%%
+
+/* Tests multiple levels of yyresolveLocations recursion.  */
+start: ambig1 | ambig2 ;
+ambig1: sub_ambig1 | sub_ambig2 ;
+ambig2: sub_ambig1 | sub_ambig2 ;
+
+/* Tests non-empty RHS as well as empty RHS with either initial location or
+   location of previous token.  Both empty RHS locations are printed in the
+   error message.  */
+sub_ambig1: empty 'a' 'b' empty ;
+sub_ambig2: empty 'a' 'b' empty ;
+empty: ;
+
+%%
+
+static void
+yyerror (YYLTYPE *locp, char const *msg)
+{
+  fprintf (stderr, "Error at %d.%d-%d.%d: %s.\n", locp->first_line,
+          locp->first_column, locp->last_line, locp->last_column, msg);
+}
+
+/*ARGSUSED*/ static int
+yylex (YYSTYPE *lvalp, YYLTYPE *llocp)
+{
+  static const char input[] = "ab";
+  static const char *inputp = input;
+  llocp->first_line = llocp->last_line = 2;
+  llocp->first_column = inputp - input + 1;
+  llocp->last_column = llocp->first_column + 1;
+  return *inputp++;
+}
+
+int
+main (void)
+{
+  return yyparse () != 1;
+}
+]])
+
+AT_CHECK([[bison -o glr-regr17.c glr-regr17.y]], 0, [],
+[glr-regr17.y: conflicts: 3 reduce/reduce
+])
+AT_COMPILE([glr-regr17])
+
+AT_CHECK([[./glr-regr17]], 0, [],
+[Error at 1.1-2.3: syntax is ambiguous.
+])
+
+AT_CLEANUP