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* src/parse-gram.y: Define PERCENT_EXPECT_RR.

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(declaration): Replace expected_conflicts with expected_sr_conflicts.
Add %expect-rr rule.

* src/scan-gram.l: Recognize %expect-rr.

* src/conflicts.h (expected_sr_conflicts): Rename from
expected_conflicts.
(expected_rr_conflicts): Declare.

* src/conflicts.c (expected_sr_conflicts): Rename from
expected_conflicts.
(expected_rr_conflicts): Define.
(conflicts_print): Check r/r conflicts against expected_rr_conflicts
for GLR parsers.
Use expected_sr_conflicts in place of expected_conflicts.
Warn if expected_rr_conflicts used in non-GLR parser.

* doc/bison.texinfo: Add documentation for %expect-rr.
This commit is contained in:
Paul Hilfinger
2004-03-26 22:41:16 +00:00
parent 1452af69b4
commit d63282419d
8 changed files with 444 additions and 380 deletions
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17
doc/bison.texinfo
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@@ -223,7 +223,7 @@ Bison Declarations
* Union Decl:: Declaring the set of all semantic value types.
* Type Decl:: Declaring the choice of type for a nonterminal symbol.
* Destructor Decl:: Declaring how symbols are freed.
* Expect Decl:: Suppressing warnings about shift/reduce conflicts.
* Expect Decl:: Suppressing warnings about parsing conflicts.
* Start Decl:: Specifying the start symbol.
* Pure Decl:: Requesting a reentrant parser.
* Decl Summary:: Table of all Bison declarations.
@@ -3280,7 +3280,7 @@ Grammars}).
* Union Decl:: Declaring the set of all semantic value types.
* Type Decl:: Declaring the choice of type for a nonterminal symbol.
* Destructor Decl:: Declaring how symbols are freed.
* Expect Decl:: Suppressing warnings about shift/reduce conflicts.
* Expect Decl:: Suppressing warnings about parsing conflicts.
* Start Decl:: Specifying the start symbol.
* Pure Decl:: Requesting a reentrant parser.
* Decl Summary:: Table of all Bison declarations.
@@ -3560,6 +3560,7 @@ typefull: string; // $$ = $1 applies, $1 is not destroyed.
@cindex warnings, preventing
@cindex conflicts, suppressing warnings of
@findex %expect
@findex %expect-rr
Bison normally warns if there are any conflicts in the grammar
(@pxref{Shift/Reduce, ,Shift/Reduce Conflicts}), but most real grammars
@@ -3580,6 +3581,18 @@ reduce/reduce conflicts. The usual warning is
given if there are either more or fewer conflicts, or if there are any
reduce/reduce conflicts.
For normal LALR(1) parsers, reduce/reduce conflicts are more serious,
and should be eliminated entirely. Bison will always report
reduce/reduce conflicts for these parsers. With GLR parsers, however,
both shift/reduce and reduce/reduce are routine (otherwise, there
would be no need to use GLR parsing). Therefore, it is also possible
to specify an expected number of reduce/reduce conflicts in GLR
parsers, using the declaration:
@example
%expect-rr @var{n}
@end example
In general, using @code{%expect} involves these steps:
@itemize @bullet