* Changes in version ?.? (????-??-??):
-** C++ parsers use YYRHSLOC
-
- Similarly to the C parsers, the C++ parsers now define the YYRHSLOC
- macro and use it in the default YYLLOC_DEFAULT. You are encouraged
- to use it. If, for instance, your location structure has "first"
- and "last" members, instead of
-
- # define YYLLOC_DEFAULT(Current, Rhs, N) \
- do \
- if (N) \
- { \
- (Current).first = (Rhs)[1].location.first; \
- (Current).last = (Rhs)[N].location.last; \
- } \
- else \
- { \
- (Current).first = (Current).last = (Rhs)[0].location.last; \
- } \
- while (false)
-
- use:
-
- # define YYLLOC_DEFAULT(Current, Rhs, N) \
- do \
- if (N) \
- { \
- (Current).first = YYRHSLOC (Rhs, 1).first; \
- (Current).last = YYRHSLOC (Rhs, N).last; \
- } \
- else \
- { \
- (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \
- } \
- while (false)
-
-
** Additional yylex/yyparse arguments
The new directive %param declare additional argument to both yylex
use of the %error-verbose directive is deprecated in favor of
%define parse.error "verbose".
+** Semantic predicates
+
+ The new, experimental, semantic-predicate feature allows actions of
+ the form %?{ BOOLEAN-EXPRESSION }, which cause syntax errors (as for
+ YYERROR) if the expression evaluates to 0, and are evaluated immediately
+ in GLR parsers, rather than being deferred. The result is that they
+ allow the programmer to prune possible parses based on the values of
+ runtime expressions.
+
* Changes in version 2.5 (????-??-??):
** Named References Support
Bison now warns when a character literal is not of length one. In
some future release, Bison will report an error instead.
-** Verbose error messages fixed for nonassociative tokens.
-
- When %error-verbose is specified, syntax error messages produced by
- the generated parser include the unexpected token as well as a list of
- expected tokens. Previously, this list erroneously included tokens
- that would actually induce a syntax error because conflicts for them
- were resolved with %nonassoc. Such tokens are now properly omitted
- from the list.
+** Verbose syntax error message fixes:
+
+ When %error-verbose or `#define YYERROR_VERBOSE' is specified, syntax
+ error messages produced by the generated parser include the unexpected
+ token as well as a list of expected tokens. The effect of %nonassoc
+ on these verbose messages has been corrected in two ways, but
+ additional fixes are still being implemented:
+
+*** When %nonassoc is used, there can exist parser states that accept no
+ tokens, and so the parser does not always require a lookahead token
+ in order to detect a syntax error. Because no unexpected token or
+ expected tokens can then be reported, the verbose syntax error
+ message described above is suppressed, and the parser instead
+ reports the simpler message, "syntax error". Previously, this
+ suppression was sometimes erroneously triggered by %nonassoc when a
+ lookahead was actually required. Now verbose messages are
+ suppressed only when all previous lookaheads have already been
+ shifted or discarded.
+
+*** Previously, the list of expected tokens erroneously included tokens
+ that would actually induce a syntax error because conflicts for them
+ were resolved with %nonassoc in the current parser state. Such
+ tokens are now properly omitted from the list.
+
+*** Expected token lists are still often wrong due to state merging
+ (from LALR or IELR) and default reductions, which can both add and
+ subtract valid tokens. Canonical LR almost completely fixes this
+ problem by eliminating state merging and default reductions.
+ However, there is one minor problem left even when using canonical
+ LR and even after the fixes above. That is, if the resolution of a
+ conflict with %nonassoc appears in a later parser state than the one
+ at which some syntax error is discovered, the conflicted token is
+ still erroneously included in the expected token list. We are
+ currently working on a fix to eliminate this problem and to
+ eliminate the need for canonical LR.
** Destructor calls fixed for lookaheads altered in semantic actions.
determine which destructor to call for the lookahead upon a syntax
error or upon parser return. This bug has been fixed.
-* Changes in version 2.4.3 (????-??-??):
+** C++ parsers use YYRHSLOC
+
+ Similarly to the C parsers, the C++ parsers now define the YYRHSLOC
+ macro and use it in the default YYLLOC_DEFAULT. You are encouraged
+ to use it. If, for instance, your location structure has "first"
+ and "last" members, instead of
+
+ # define YYLLOC_DEFAULT(Current, Rhs, N) \
+ do \
+ if (N) \
+ { \
+ (Current).first = (Rhs)[1].location.first; \
+ (Current).last = (Rhs)[N].location.last; \
+ } \
+ else \
+ { \
+ (Current).first = (Current).last = (Rhs)[0].location.last; \
+ } \
+ while (false)
+
+ use:
+
+ # define YYLLOC_DEFAULT(Current, Rhs, N) \
+ do \
+ if (N) \
+ { \
+ (Current).first = YYRHSLOC (Rhs, 1).first; \
+ (Current).last = YYRHSLOC (Rhs, N).last; \
+ } \
+ else \
+ { \
+ (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \
+ } \
+ while (false)
+
+** YYLLOC_DEFAULT in C++
+
+ The default implementation of YYLLOC_DEFAULT used to be issued in
+ the header file. It is now output in the implementation file, after
+ the user %code sections so that its #ifndef guard does not try to
+ override the user's YYLLOC_DEFAULT if provided.
+
+* Changes in version 2.4.3 (2010-08-05):
+
+** Bison now obeys -Werror and --warnings=error for warnings about
+ grammar rules that are useless in the parser due to conflicts.
** Problems with spawning M4 on at least FreeBSD 8 and FreeBSD 9 have
been fixed.
errors in Bison 2.5. They will remain warnings, which should be
sufficient for POSIX while avoiding backward compatibility issues.
+** Minor documentation fixes.
+
* Changes in version 2.4.2 (2010-03-20):
** Some portability problems that resulted in failures and livelocks
-----
-Copyright (C) 1995-2010 Free Software Foundation, Inc.
+Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
+2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation,
+Inc.
This file is part of Bison, the GNU Parser Generator.
projects / bison.git / blobdiff