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.
+2006-03-06 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
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
switch (yypreference (yybest, yyp))
{
case 0:
+ yyresolveLocations (yys, 1, yystackp]b4_user_args[);
return yyreportAmbiguity (yybest, yyp]b4_pure_args[);
break;
case 1:
@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.
+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 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
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.
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:
])
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
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