Bison News
----------
Changes in version 1.49b:
* Undefined token
The undefined token was systematically mapped to 2 which prevented
the use of 2 from the user. This is no longer the case.
* Unknown token numbers
If yylex returned a code out of range, yyparse could die. This is
no longer the case.
* Error token
According to POSIX, the error token should be numbered as 256.
Bison extends this requirement by making it a preference: *if* the
user specified that one of her tokens is numbered 256, then error
will be mapped onto another number.
* Error recovery now conforms to documentation and to POSIX
When a Bison-generated parser encounters a syntax error, it now pops
the stack until it finds a state that allows shifting the error
token. Formerly, it popped the stack until it found a state that
allowed some non-error action other than a default reduction on the
error token. The new behavior has long been the documented behavior,
and has long been required by POSIX. For more details, please see
<http://mail.gnu.org/pipermail/bug-bison/2002-May/001452.html>.
* Traces
Popped tokens and nonterminals are now reported.
* Large grammars
Large grammars are now supported (large token numbers, large grammar
size (= sum of the LHS and RHS lengths), large LALR tables).
* Explicit initial rule
Bison used to play hacks with the initial rule, which the user does
not write. It is now explicit, and visible in the reports and
graphs as rule 0.
* Useless rules
Before, Bison reported the useless rules, but, although not used,
included them in the parsers. They are now actually removed.
* Incorrect `Token not used'
On a grammar such as
%token useless useful
%%
exp: '0' %prec useful;
where a token was used to set the precedence of the last rule,
bison reported both `useful' and `useless' as useless tokens.
* Revert the C++ namespace changes introduced in 1.31
as they caused too many portability hassles.
* Default locations
By an accident of design, the default computation of @$ was
performed after another default computation was performed: @$ = @1.
The latter is now removed: YYLLOC_DEFAULT is fully responsible of
the computation of @$.
* Token end-of-file
The token end of file may be specified by the user, in which case,
the user symbol is used in the reports, the graphs, and the verbose
error messages instead of `$', which remains being the defaults.
For instance
%token YYEOF 0
or
%token YYEOF 0 "end of file"
* Semantic parser
This old option, which has been broken for ages, is removed.
* New translation
Croatian, thanks to Denis Lackovic.
* Incorrect token definitions
When fed with `%token 'a' "A"', Bison used to output `#define 'a' 65'.
* Token definitions as enums
Tokens are output both as the traditional #define's, and, provided
the compiler supports ANSI C or is a C++ compiler, as enums.
This helps debuggers producing symbols instead of values.
* Reports
In addition to --verbose, bison supports --report=THINGS, which
produces additional information:
- itemset
complete the core item sets with their closure
- lookahead
explicitly associate lookaheads to items
- solved
describe shift/reduce conflicts solving.
Bison used to systematically output this information on top of
the report. Solved conflicts are now attached to their states.
Changes in version 1.35, 2002-03-25:
* C Skeleton
Some projects use Bison's C parser with C++ compilers, and define
YYSTYPE as a class. The recent adjustment of C parsers for data
alignment and 64 bit architectures made this impossible.
Because for the time being no real solution for C++ parser
generation exists, kludges were implemented in the parser to
maintain this use. In the future, when Bison has C++ parsers, this
kludge will be disabled.
This kludge also addresses some C++ problems when the stack was
extended.
Changes in version 1.34, 2002-03-12:
* File name clashes are detected
$ bison foo.y -d -o foo.x
fatal error: header and parser would both be named `foo.x'
* A missing `;' at the end of a rule triggers a warning
In accordance with POSIX, and in agreement with other
Yacc implementations, Bison will mandate this semicolon in the near
future. This eases the implementation of a Bison parser of Bison
grammars by making this grammar LALR(1) instead of LR(2). To
facilitate the transition, this release introduces a warning.
* Revert the C++ namespace changes introduced in 1.31, as they caused too
many portability hassles.
* DJGPP support added.
* Fix test suite portability problems.
Changes in version 1.33, 2002-02-07:
* Fix C++ issues
Groff could not be compiled for the definition of size_t was lacking
under some conditions.
* Catch invalid @n
As is done with $n.
Changes in version 1.32, 2002-01-23:
* Fix Yacc output file names
* Portability fixes
* Italian, Dutch translations
Changes in version 1.31, 2002-01-14:
* Many Bug Fixes
* GNU Gettext and %expect
GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that
Bison dies on incorrect %expectations, we fear there will be
too many bug reports for Gettext, so _for the time being_, %expect
does not trigger an error when the input file is named `plural.y'.
* Use of alloca in parsers
If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
malloc exclusively. Since 1.29, but was not NEWS'ed.
alloca is used only when compiled with GCC, to avoid portability
problems as on AIX.
* When the generated parser lacks debugging code, YYDEBUG is now 0
(as POSIX requires) instead of being undefined.
* User Actions
Bison has always permitted actions such as { $$ = $1 }: it adds the
ending semicolon. Now if in Yacc compatibility mode, the semicolon
is no longer output: one has to write { $$ = $1; }.
* Better C++ compliance
The output parsers try to respect C++ namespaces.
[This turned out to be a failed experiment, and it was reverted later.]
* Reduced Grammars
Fixed bugs when reporting useless nonterminals.
* 64 bit hosts
The parsers work properly on 64 bit hosts.
* Error messages
Some calls to strerror resulted in scrambled or missing error messages.
* %expect
When the number of shift/reduce conflicts is correct, don't issue
any warning.
* The verbose report includes the rule line numbers.
* Rule line numbers are fixed in traces.
* Swedish translation
* Parse errors
Verbose parse error messages from the parsers are better looking.
Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
Now: parse error: unexpected '/', expecting "number" or '-' or '('
* Fixed parser memory leaks.
When the generated parser was using malloc to extend its stacks, the
previous allocations were not freed.
* Fixed verbose output file.
Some newlines were missing.
Some conflicts in state descriptions were missing.
* Fixed conflict report.
Option -v was needed to get the result.
* %expect
Was not used.
Mismatches are errors, not warnings.
* Fixed incorrect processing of some invalid input.
* Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
* Fixed some typos in the documentation.
* %token MY_EOF 0 is supported.
Before, MY_EOF was silently renumbered as 257.
* doc/refcard.tex is updated.
* %output, %file-prefix, %name-prefix.
New.
* --output
New, aliasing `--output-file'.
Changes in version 1.30, 2001-10-26:
* `--defines' and `--graph' have now an optionnal argument which is the
output file name. `-d' and `-g' do not change, they do not take any
argument.
* `%source_extension' and `%header_extension' are removed, failed
experiment.
* Portability fixes.
Changes in version 1.29, 2001-09-07:
* The output file does not define const, as this caused problems when used
with common autoconfiguration schemes. If you still use ancient compilers
that lack const, compile with the equivalent of the C compiler option
`-Dconst='. autoconf's AC_C_CONST macro provides one way to do this.
* Added `-g' and `--graph'.
* The Bison manual is now distributed under the terms of the GNU FDL.
* The input and the output files has automatically a similar extension.
* Russian translation added.
* NLS support updated; should hopefully be less troublesome.
* Added the old Bison reference card.
* Added `--locations' and `%locations'.
* Added `-S' and `--skeleton'.
* `%raw', `-r', `--raw' is disabled.
* Special characters are escaped when output. This solves the problems
of the #line lines with path names including backslashes.
* New directives.
`%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
`%debug', `%source_extension' and `%header_extension'.
* @$
Automatic location tracking.
Changes in version 1.28, 1999-07-06:
* Should compile better now with K&R compilers.
* Added NLS.
* Fixed a problem with escaping the double quote character.
* There is now a FAQ.
Changes in version 1.27:
* The make rule which prevented bison.simple from being created on
some systems has been fixed.
Changes in version 1.26:
* Bison now uses automake.
* New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
* Token numbers now start at 257 as previously documented, not 258.
* Bison honors the TMPDIR environment variable.
* A couple of buffer overruns have been fixed.
* Problems when closing files should now be reported.
* Generated parsers should now work even on operating systems which do
not provide alloca().
Changes in version 1.25, 1995-10-16:
* Errors in the input grammar are not fatal; Bison keeps reading
the grammar file, and reports all the errors found in it.
* Tokens can now be specified as multiple-character strings: for
example, you could use "<=" for a token which looks like <=, instead
of chosing a name like LESSEQ.
* The %token_table declaration says to write a table of tokens (names
and numbers) into the parser file. The yylex function can use this
table to recognize multiple-character string tokens, or for other
purposes.
* The %no_lines declaration says not to generate any #line preprocessor
directives in the parser file.
* The %raw declaration says to use internal Bison token numbers, not
Yacc-compatible token numbers, when token names are defined as macros.
* The --no-parser option produces the parser tables without including
the parser engine; a project can now use its own parser engine.
The actions go into a separate file called NAME.act, in the form of
a switch statement body.
Changes in version 1.23:
The user can define YYPARSE_PARAM as the name of an argument to be
passed into yyparse. The argument should have type void *. It should
actually point to an object. Grammar actions can access the variable
by casting it to the proper pointer type.
Line numbers in output file corrected.
Changes in version 1.22:
--help option added.
Changes in version 1.20:
Output file does not redefine const for C++.
Local Variables:
mode: outline
End:
-----
Copyright (C) 2001, 2002 Free Software Foundation, Inc.
This file is part of GNU Autoconf.
GNU Autoconf is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Autoconf is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with autoconf; see the file COPYING. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.