* Noteworthy changes in release ?.? (????-??-??) [?]
+** Incompatible changes
+
+*** Obsolete features
+
+ Support for YYFAIL is removed (deprecated in Bison 2.4.2).
+ Support for yystype and yyltype (instead of YYSTYPE and YYLTYPE)
+ is removed (deprecated in Bison 1.875).
+ Support for YYPARSE_PARAM is removed (deprecated in Bison 1.875).
+
+** Warnings
+
+*** Enhancements of the -Werror option
+
+ The -Werror=CATEGORY option is now recognized, and will treat specified
+ warnings as errors. The warnings need not have been explicitly activated
+ using the -W option, this is similar to what GCC 4.7 does.
+
+ For example, given the following command line, Bison will treat both
+ warnings related to POSIX Yacc incompatibilities and S/R conflicts as
+ errors (and only those):
+
+ $ bison -Werror=yacc,error=conflicts-sr input.y
+
+ If no categories are specified, -Werror will make all active warnings into
+ errors. For example, the following line does the same the previous example:
+
+ $ bison -Werror -Wnone -Wyacc -Wconflicts-sr input.y
+
+ (By default -Wconflicts-sr,conflicts-rr,deprecated,other is enabled.)
+
+ Note that the categories in this -Werror option may not be prefixed with
+ "no-". However, -Wno-error[=CATEGORY] is valid.
+
+ Note that -y enables -Werror=yacc. Therefore it is now possible to require
+ Yacc-like behavior (e.g., always generate y.tab.c), but to report
+ incompatibilities as warnings: "-y -Wno-error=yacc".
+
+*** The display of warnings is now richer
+
+ The option that controls a given warning is now displayed:
+
+ foo.y:4.6: warning: type clash on default action: <foo> != <bar> [-Wother]
+
+ In the case of warnings treated as errors, the prefix is changed from
+ "warning: " to "error: ", and the suffix is displayed, in a manner similar
+ to GCC, as [-Werror=CATEGORY].
+
+ For instance, where the previous version of Bison would report (and exit
+ with failure):
+
+ bison: warnings being treated as errors
+ input.y:1.1: warning: stray ',' treated as white space
+
+ it now reports:
+
+ input.y:1.1: error: stray ',' treated as white space [-Werror=other]
+
+*** Deprecated constructs
+
+ The new 'deprecated' warning category flags obsolete constructs whose
+ support will be discontinued. It is enabled by default. These warnings
+ used to be reported as 'other' warnings.
+
+*** Useless semantic types
+
+ Bison now warns about useless (uninhabited) semantic types. Since
+ semantic types are not declared to Bison (they are defined in the opaque
+ %union structure), it is %printer/%destructor directives about useless
+ types that trigger the warning:
+
+ %token <type1> term
+ %type <type2> nterm
+ %printer {} <type1> <type3>
+ %destructor {} <type2> <type4>
+ %%
+ nterm: term { $$ = $1; };
+
+ 3.28-34: warning: type <type3> is used, but is not associated to any symbol
+ 4.28-34: warning: type <type4> is used, but is not associated to any symbol
+
+*** Undefined but unused symbols
+
+ Bison used to raise an error for undefined symbols that are not used in
+ the grammar. This is now only a warning.
+
+ %printer {} symbol1
+ %destructor {} symbol2
+ %type <type> symbol3
+ %%
+ exp: "a";
+
+*** Useless destructors or printers
+
+ Bison now warns about useless destructors or printers. In the following
+ example, the printer for <type1>, and the destructor for <type2> are
+ useless: all symbols of <type1> (token1) already have a printer, and all
+ symbols of type <type2> (token2) already have a destructor.
+
+ %token <type1> token1
+ <type2> token2
+ <type3> token3
+ <type4> token4
+ %printer {} token1 <type1> <type3>
+ %destructor {} token2 <type2> <type4>
+
+*** Conflicts
+
+ The warnings and error messages about shift/reduce and reduce/reduce
+ conflicts have been normalized. For instance on the following foo.y file:
+
+ %glr-parser
+ %%
+ exp: exp '+' exp | '0' | '0';
+
+ compare the previous version of bison:
+
+ $ bison foo.y
+ foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce
+ $ bison -Werror foo.y
+ bison: warnings being treated as errors
+ foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce
+
+ with the new behavior:
+
+ $ bison foo.y
+ foo.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
+ foo.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr]
+ $ bison -Werror foo.y
+ foo.y: error: 1 shift/reduce conflict [-Werror=conflicts-sr]
+ foo.y: error: 2 reduce/reduce conflicts [-Werror=conflicts-rr]
+
+ When %expect or %expect-rr is used, such as with bar.y:
+
+ %expect 0
+ %glr-parser
+ %%
+ exp: exp '+' exp | '0' | '0';
+
+ Former behavior:
+
+ $ bison bar.y
+ bar.y: conflicts: 1 shift/reduce, 2 reduce/reduce
+ bar.y: expected 0 shift/reduce conflicts
+ bar.y: expected 0 reduce/reduce conflicts
+
+ New one:
+
+ $ bison bar.y
+ bar.y: error: shift/reduce conflicts: 1 found, 0 expected
+ bar.y: error: reduce/reduce conflicts: 2 found, 0 expected
+
+** Additional yylex/yyparse arguments
+
+ The new directive %param declares additional arguments to both yylex and
+ yyparse. The %lex-param, %parse-param, and %param directives support one
+ or more arguments. Instead of
+
+ %lex-param {arg1_type *arg1}
+ %lex-param {arg2_type *arg2}
+ %parse-param {arg1_type *arg1}
+ %parse-param {arg2_type *arg2}
+
+ one may now declare
+
+ %param {arg1_type *arg1} {arg2_type *arg2}
+
+** Java skeleton improvements
+
+ The constants for token names were moved to the Lexer interface. Also, it
+ is possible to add code to the parser's constructors using "%code init"
+ and "%define init_throws".
+
+** C++ skeletons improvements
+
+*** The parser header is no longer mandatory (lalr1.cc, glr.cc)
+
+ Using %defines is now optional. Without it, the needed support classes
+ are defined in the generated parser, instead of additional files (such as
+ location.hh, position.hh and stack.hh).
+
+*** Locations are no longer mandatory (lalr1.cc, glr.cc)
+
+ Both lalr1.cc and glr.cc no longer require %location.
+
+*** syntax_error exception (lalr1.cc)
+
+ The C++ parser features a syntax_error exception, which can be
+ thrown from the scanner or from user rules to raise syntax errors.
+ This facilitates reporting errors caught in sub-functions (e.g.,
+ rejecting too large integral literals from a conversion function
+ used by the scanner, or rejecting invalid combinations from a
+ factory invoked by the user actions).
+
+** Variable api.token.prefix
+
+ The variable api.token.prefix changes the way tokens are identified in
+ the generated files. This is especially useful to avoid collisions
+ with identifiers in the target language. For instance
+
+ %token FILE for ERROR
+ %define api.token.prefix "TOK_"
+ %%
+ start: FILE for ERROR;
+
+ will generate the definition of the symbols TOK_FILE, TOK_for, and
+ TOK_ERROR in the generated sources. In particular, the scanner must
+ use these prefixed token names, although the grammar itself still
+ uses the short names (as in the sample rule given above).
+
+** Renamed %define variables
+
+ The following variables have been renamed for consistency. Backward
+ compatibility is ensured, but upgrading is recommended.
+
+ lr.default-reductions -> lr.default-reduction
+ lr.keep-unreachable-states -> lr.keep-unreachable-state
+ namespace -> api.namespace
+
+** Variable parse.error
+
+ This variable controls the verbosity of error messages. The 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 run-time
+ expressions.
+
+** The directive %expect-rr is now an error in non GLR mode
+
+ It used to be an error only if used in non GLR mode, _and_ if there are
+ reduce/reduce conflicts.
+
+* Noteworthy changes in release ?.? (????-??-??) [?]
+
+ ** New value for %define variable: api.pure full
+
+ The %define variable api.pure requests a pure (reentrant) parser. However,
+ for historical reasons, using it in a location-tracking Yacc parser resulted
+ in an yyerror function that did not take a location as a parameter. With this
+ new value, the user may request a better pure parser, where yyerror does take
+ a location as a parameter (in location-tracking parsers).
+
+ The use of "%define api.pure true" is deprecated in favor of this new
+ "%define api.pure full".
+
** Changes in the format of error messages
This used to be the format of many error reports:
# ---------------
# Arguments passed to yyerror: user args plus yylloc.
m4_define([b4_yyerror_args],
- [b4_yacc_pure_if([b4_locations_if([&yylloc, ])])dnl
+ [b4_yyerror_arg_loc_if([&yylloc, ])dnl
-m4_ifset([b4_parse_param], [b4_c_args(b4_parse_param), ])])
+m4_ifset([b4_parse_param], [b4_args(b4_parse_param), ])])
# b4_lex_param
@item Purpose: Request a pure (reentrant) parser program.
@xref{Pure Decl, ,A Pure (Reentrant) Parser}.
- @item Accepted Values: Boolean
+ @item Accepted Values: @code{true}, @code{false}, @code{full}
+
+ The value may be omitted: this is equivalent to specifying @code{true}, as is
+ the case for Boolean values.
+
+ When @code{%define api.pure full} is used, the parser is made reentrant. This
+ changes the signature for @code{yylex} (@pxref{Pure Calling}), and also that of
+ @code{yyerror} when the tracking of locations has been activated, as shown
+ below.
+
+ The @code{true} value is very similar to the @code{full} value, the only
+ difference is in the signature of @code{yyerror} on Yacc parsers without
+ @code{%parse-param}, for historical reasons.
+
+ I.e., if @samp{%locations %define api.pure} is passed then the prototypes for
+ @code{yyerror} are:
+
+ @example
+ void yyerror (char const *msg); /* Yacc parsers. */
+ void yyerror (YYLTYPE *locp, char const *msg); /* GLR parsers. */
+ @end example
+
+ But if @samp{%locations %define api.pure %parse-param @{int *nastiness@}} is
+ used, then both parsers have the same signature:
+
+ @example
+ void yyerror (YYLTYPE *llocp, int *nastiness, char const *msg);
+ @end example
+
+ (@pxref{Error Reporting, ,The Error
+ Reporting Function @code{yyerror}})
@item Default Value: @code{false}
+
+ @item History: the @code{full} value was introduced in Bison 2.7
@end itemize
+@c api.pure
+
-@c ================================================== api.push-pull
-@item @code{api.push-pull}
+@c ================================================== api.push-pull
+@item api.push-pull
@findex %define api.push-pull
@itemize @bullet
@item Accepted Values: Boolean
@item Default Value: @code{false}
@end itemize
- @code{lr.keep-unreachable-state} in 2.5, and as
+introduced as @code{lr.keep_unreachable_states} in 2.3b, renamed as
++@code{lr.keep-unreachable-states} in 2.5, and as
+@code{lr.keep-unreachable-state} in 2.8.
+@c lr.keep-unreachable-state
@c ================================================== lr.type
this case, omit the second argument; @code{yylex} will be called with
only one argument.
-
-If you wish to pass the additional parameter data to @code{yylex}, use
+If you wish to pass additional arguments to @code{yylex}, use
@code{%lex-param} just like @code{%parse-param} (@pxref{Parser
-Function}).
+Function}). To pass additional arguments to both @code{yylex} and
+@code{yyparse}, use @code{%param}.
-@deffn {Directive} lex-param @{@var{argument-declaration}@}
+@deffn {Directive} %lex-param @{@var{argument-declaration}@} @dots{}
@findex %lex-param
-Declare that the braced-code @var{argument-declaration} is an
-additional @code{yylex} argument declaration.
+Specify that @var{argument-declaration} are additional @code{yylex} argument
+declarations. You may pass one or more such declarations, which is
+equivalent to repeating @code{%lex-param}.
+@end deffn
+
+@deffn {Directive} %param @{@var{argument-declaration}@} @dots{}
+@findex %param
+Specify that @var{argument-declaration} are additional
+@code{yylex}/@code{yyparse} argument declaration. This is equivalent to
+@samp{%lex-param @{@var{argument-declaration}@} @dots{} %parse-param
+@{@var{argument-declaration}@} @dots{}}. You may pass one or more
+declarations, which is equivalent to repeating @code{%param}.
@end deffn
+ @noindent
For instance:
@example
@end example
@noindent
-results in the following signature:
+results in the following signatures:
@example
-int yylex (int *nastiness);
+int yylex (scanner_mode *mode, environment_type *env);
+int yyparse (parser_mode *mode, environment_type *env);
+@end example
+
- If @samp{%define api.pure} is added:
++If @samp{%define api.pure full} is added:
+
+@example
+int yylex (YYSTYPE *lvalp, scanner_mode *mode, environment_type *env);
+int yyparse (parser_mode *mode, environment_type *env);
@end example
@noindent
- and finally, if both @samp{%define api.pure} and @code{%locations} are used:
-If @code{%define api.pure full} (or just @code{%define api.pure}) is added:
++and finally, if both @samp{%define api.pure full} and @code{%locations} are
++used:
@example
-int yylex (YYSTYPE *lvalp, int *nastiness);
+int yylex (YYSTYPE *lvalp, YYLTYPE *llocp,
+ scanner_mode *mode, environment_type *env);
+int yyparse (parser_mode *mode, environment_type *env);
@end example
@node Error Reporting
split the parse instead.
To adjust which states have default reductions enabled, use the
-@code{%define lr.default-reductions} directive.
+@code{%define lr.default-reduction} directive.
- @deffn {Directive} {%define lr.default-reduction @var{WHERE}}
-@deffn {Directive} {%define lr.default-reductions} @var{where}
++@deffn {Directive} {%define lr.default-reduction} @var{where}
Specify the kind of states that are permitted to contain default reductions.
- The accepted values of @var{WHERE} are:
+ The accepted values of @var{where} are:
@itemize
@item @code{most} (default for LALR and IELR)
@item @code{consistent}
keeping unreachable states is sometimes useful when trying to understand the
relationship between the parser and the grammar.
- @deffn {Directive} {%define lr.keep-unreachable-state @var{VALUE}}
-@deffn {Directive} {%define lr.keep-unreachable-states} @var{value}
++@deffn {Directive} {%define lr.keep-unreachable-state} @var{value}
Request that Bison allow unreachable states to remain in the parser tables.
- @var{VALUE} must be a Boolean. The default is @code{false}.
+ @var{value} must be a Boolean. The default is @code{false}.
@end deffn
There are a few caveats to consider:
The parser invokes the scanner by calling @code{yylex}. Contrary to C
parsers, C++ parsers are always pure: there is no point in using the
-@code{%define api.pure full} directive. Therefore the interface is as follows.
+@samp{%define api.pure} directive. The actual interface with @code{yylex}
+depends whether you use unions, or variants.
+
+@menu
+* Split Symbols:: Passing symbols as two/three components
+* Complete Symbols:: Making symbols a whole
+@end menu
+
+@node Split Symbols
+@subsubsection Split Symbols
+
- Therefore the interface is as follows.
++The interface is as follows.
@deftypemethod {parser} {int} yylex (semantic_type* @var{yylval}, location_type* @var{yylloc}, @var{type1} @var{arg1}, ...)
-Return the next token. Its type is the return value, its semantic
-value and location being @var{yylval} and @var{yylloc}. Invocations of
+@deftypemethodx {parser} {int} yylex (semantic_type* @var{yylval}, @var{type1} @var{arg1}, ...)
+Return the next token. Its type is the return value, its semantic value and
+location (if enabled) being @var{yylval} and @var{yylloc}. Invocations of
@samp{%lex-param @{@var{type1} @var{arg1}@}} yield additional arguments.
@end deftypemethod
Contrary to C parsers, Java parsers do not use global variables; the
state of the parser is always local to an instance of the parser class.
Therefore, all Java parsers are ``pure'', and the @code{%pure-parser}
- and @samp{%define api.pure} directives does not do anything when used in
-and @code{%define api.pure full} directives does not do anything when used in
--Java.
++and @code{%define api.pure} directives do nothing when used in Java.
Push parsers are currently unsupported in Java and @code{%define
api.push-pull} have no effect.
AT_CHECK_CALC_LALR([%defines])
AT_CHECK_CALC_LALR([%locations])
-AT_CHECK_CALC_LALR([%name-prefix="calc"]) dnl test deprecated `='
+AT_CHECK_CALC_LALR([%name-prefix "calc"])
AT_CHECK_CALC_LALR([%verbose])
AT_CHECK_CALC_LALR([%yacc])
-AT_CHECK_CALC_LALR([%error-verbose])
+AT_CHECK_CALC_LALR([%define parse.error verbose])
- AT_CHECK_CALC_LALR([%define api.pure %locations])
- AT_CHECK_CALC_LALR([%define api.push-pull both %define api.pure %locations])
+ AT_CHECK_CALC_LALR([%define api.pure full %locations])
+ AT_CHECK_CALC_LALR([%define api.push-pull both %define api.pure full %locations])
-AT_CHECK_CALC_LALR([%error-verbose %locations])
+AT_CHECK_CALC_LALR([%define parse.error verbose %locations])
-AT_CHECK_CALC_LALR([%error-verbose %locations %defines %name-prefix "calc" %verbose %yacc])
-AT_CHECK_CALC_LALR([%error-verbose %locations %defines %define api.prefix "calc" %verbose %yacc])
+AT_CHECK_CALC_LALR([%define parse.error verbose %locations %defines %define api.prefix "calc" %verbose %yacc])
+AT_CHECK_CALC_LALR([%define parse.error verbose %locations %defines %name-prefix "calc" %define api.token.prefix "TOK_" %verbose %yacc])
AT_CHECK_CALC_LALR([%debug])
-AT_CHECK_CALC_LALR([%error-verbose %debug %locations %defines %name-prefix "calc" %verbose %yacc])
-AT_CHECK_CALC_LALR([%error-verbose %debug %locations %defines %define api.prefix "calc" %verbose %yacc])
+AT_CHECK_CALC_LALR([%define parse.error verbose %debug %locations %defines %name-prefix "calc" %verbose %yacc])
+AT_CHECK_CALC_LALR([%define parse.error verbose %debug %locations %defines %define api.prefix "calc" %verbose %yacc])
- AT_CHECK_CALC_LALR([%define api.pure %define parse.error verbose %debug %locations %defines %name-prefix "calc" %verbose %yacc])
- AT_CHECK_CALC_LALR([%define api.push-pull both %define api.pure %define parse.error verbose %debug %locations %defines %define api.prefix "calc" %verbose %yacc])
-AT_CHECK_CALC_LALR([%define api.pure full %verbose %debug %locations %defines %name-prefix "calc" %verbose %yacc])
-AT_CHECK_CALC_LALR([%define api.push-pull both %define api.pure full %verbose %debug %locations %defines %define api.prefix "calc" %verbose %yacc])
++AT_CHECK_CALC_LALR([%define api.pure full %define parse.error verbose %debug %locations %defines %name-prefix "calc" %verbose %yacc])
++AT_CHECK_CALC_LALR([%define api.push-pull both %define api.pure full %define parse.error verbose %debug %locations %defines %define api.prefix "calc" %verbose %yacc])
-AT_CHECK_CALC_LALR([%define api.pure %error-verbose %debug %locations %defines %define api.prefix "calc" %verbose %yacc %parse-param {semantic_value *result} %parse-param {int *count}])
+AT_CHECK_CALC_LALR([%define api.pure %define parse.error verbose %debug %locations %defines %define api.prefix "calc" %verbose %yacc %parse-param {semantic_value *result} %parse-param {int *count}])
# ----------------------- #
[yy])])
m4_pushdef([AT_API_PREFIX],
[m4_toupper(AT_API_prefix)])
- # yyerror receives the location if %location & %pure & (%glr or %parse-param).
+ # yyerror receives the location if %location, and if the parser is pure. For
+ # historical reasons, with the "yacc.c" skeleton, the location is not passed
+ # unless an additional "%parse-param" is present, or if the purity is defined
+ # as "full".
m4_pushdef([AT_YYERROR_ARG_LOC_IF],
- [AT_GLR_OR_PARAM_IF([AT_PURE_AND_LOC_IF([$1], [$2])],
+ [AT_LOCATION_IF([AT_PURE_IF([m4_bmatch([$3],
+ m4_quote(m4_join([\|],
+ [%define api.pure "?full"?],
+ [%glr-parser],
+ [%parse-param],
+ [%skeleton "?glr.c"?])),
+ [$1], [$2])],
+ [$2])],
- [$2])])
+ [$2])])
- # yyerror always sees the locations (when activated), except if
- # (yacc & pure & !param). FIXME: This is wrong. See the manual.
+
+ # yyerror always sees the locations (when activated) if the parser is impure.
+ # When the parser is pure, yyerror sees the location if it is received as an
+ # argument.
m4_pushdef([AT_YYERROR_SEES_LOC_IF],
- [AT_LOCATION_IF([AT_YACC_IF([AT_PURE_IF([AT_PARAM_IF([$1], [$2])],
+ [AT_LOCATION_IF([AT_YACC_IF([AT_PURE_IF([AT_YYERROR_ARG_LOC_IF([$1], [$2])],
[$1])],
[$1])],
[$2])])
m4_popdef([AT_YYERROR_ARG_LOC_IF])
m4_popdef([AT_API_PREFIX])
m4_popdef([AT_API_prefix])
+m4_popdef([AT_TOKEN_PREFIX])
+m4_popdef([AT_TOKEN_CTOR_IF])
m4_popdef([AT_NAME_PREFIX])
- m4_popdef([AT_GLR_OR_PARAM_IF])
- m4_popdef([AT_PURE_AND_LOC_IF])
m4_popdef([AT_LOCATION_TYPE_IF])
m4_popdef([AT_LOCATION_IF])
m4_popdef([AT_PARSE_PARAMS])
projects / bison.git / commitdiff
