Bison News
----------
-Changes in version 1.49b:
+Changes in version 1.75a:
+
+* Bison can no longer be built by a K&R C compiler; it requires C89 or
+ later to be built. This change originally took place a few versions
+ ago, but nobody noticed until we recently asked someone to try
+ building Bison with a K&R C compiler.
+
+Changes in version 1.75:
+
+* Bison should now work on 64-bit hosts.
+
+* Indonesian translation thanks to Tedi Heriyanto.
+
+* GLR parsers
+ Fix spurious parse errors.
+
+* Pure parsers
+ Some people redefine yyerror to steal yyparse' private variables.
+ Reenable this trick until an official feature replaces it.
+
+* Type Clashes
+ In agreement with POSIX and with other Yaccs, leaving a default
+ action is valid when $$ is untyped, and $1 typed:
+
+ untyped: ... typed;
+
+ but the converse remains an error:
+
+ typed: ... untyped;
+
+* Values of mid-rule actions
+ The following code:
+
+ foo: { ... } { $$ = $1; } ...
+
+ was incorrectly rejected: $1 is defined in the second mid-rule
+ action, and is equal to the $$ of the first mid-rule action.
+
+Changes in version 1.50, 2002-10-04:
+
+* GLR parsing
+ The declaration
+ %glr-parser
+ causes Bison to produce a Generalized LR (GLR) parser, capable of handling
+ almost any context-free grammar, ambiguous or not. The new declarations
+ %dprec and %merge on grammar rules allow parse-time resolution of
+ ambiguities. Contributed by Paul Hilfinger.
+
+ Unfortunately Bison 1.50 does not work properly on 64-bit hosts
+ like the Alpha, so please stick to 32-bit hosts for now.
+
+* Output Directory
+ When not in Yacc compatibility mode, when the output file was not
+ specified, running `bison foo/bar.y' created `foo/bar.c'. It
+ now creates `bar.c'.
* 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.
+ the use of 2 by the user. This is no longer the case.
-* Undefined token
- If yylex returned a code out of range, yyparse could die. This is
+* Unknown token numbers
+ If yylex returned an out of range value, yyparse could die. This is
no longer the case.
* Error token
- According to POSIX, the error token should be numbered as 256.
+ According to POSIX, the error token must be 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.
-* Large grammars
- Are now supported (large token numbers, large grammar size (= sum of
- the LHS and RHS lengths), large LALR tables).
+* Verbose error messages
+ They no longer report `..., expecting error or...' for states where
+ error recovery is possible.
+
+* End token
+ Defaults to `$end' instead of `$'.
+
+* 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.
-* The initial rule is explicit.
+* Larger grammars
+ Larger grammars are now supported (larger token numbers, larger grammar
+ size (= sum of the LHS and RHS lengths), larger LALR tables).
+ Formerly, many of these numbers ran afoul of 16-bit limits;
+ now these limits are 32 bits on most hosts.
+
+* 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 are actually removed.
+* Useless rules
Before, Bison reported the useless rules, but, although not used,
- included them in the parsers.
+ included them in the parsers. They are now actually removed.
+
+* Useless rules, useless nonterminals
+ They are now reported, as a warning, with their locations.
-* False `Token not used' report fixed.
+* Rules never reduced
+ Rules that can never be reduced because of conflicts are now
+ reported.
+
+* Incorrect `Token not used'
On a grammar such as
%token useless 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.
+* 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
* 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 `$', which remains being the defaults.
+ error messages instead of `$end', which remains being the default.
For instance
%token YYEOF 0
or
* Semantic parser
This old option, which has been broken for ages, is removed.
-* New tranlations
+* New translations
+ Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
Croatian, thanks to Denis Lackovic.
-* Token definitions
- When fed with `%token 'a' "A"', Bison used to output `#define 'a' 65'.
-
+* Incorrect token definitions
+ When given `%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 lets debuggers display names instead of integers.
+
+* 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.
+
+* Type clashes
+ Previous versions don't complain when there is a type clash on
+ the default action if the rule has a mid-rule action, such as in:
+
+ %type <foo> bar
+ %%
+ bar: '0' {} '0';
+
+ This is fixed.
+
+* GNU M4 is now required when using Bison.
\f
Changes in version 1.35, 2002-03-25:
This kludge also addresses some C++ problems when the stack was
extended.
-
\f
Changes in version 1.34, 2002-03-12:
projects / bison.git / blobdiff