* Noteworthy changes in release ?.? (????-??-??) [?]
-** Warnings about useless semantic types
+** Bug fixes
+
+*** Location of errors
+
+ In C++ parsers, out-of-bounds errors can happen when a rule with an empty
+ ride-hand side raises a syntax error. The behavior of the default parser
+ (yacc.c) in such a condition was undefined.
+
+ Now all the parsers match the behavior of glr.c: @$ is used as the
+ location of the error. This handles gracefully rules with and without
+ rhs.
+
+* Noteworthy changes in release 3.0.4 (2015-01-23) [stable]
+
+** Bug fixes
+
+*** C++ with Variants (lalr1.cc)
+
+ Fix a compiler warning when no %destructor use $$.
+
+*** Test suites
+
+ Several portability issues in tests were fixed.
+
+* Noteworthy changes in release 3.0.3 (2015-01-15) [stable]
+
+** Bug fixes
+
+*** C++ with Variants (lalr1.cc)
+
+ Problems with %destructor and '%define parse.assert' have been fixed.
+
+*** Named %union support (yacc.c, glr.c)
+
+ Bison 3.0 introduced a regression on named %union such as
+
+ %union foo { int ival; };
+
+ The possibility to use a name was introduced "for Yacc compatibility".
+ It is however not required by POSIX Yacc, and its usefulness is not clear.
+
+*** %define api.value.type union with %defines (yacc.c, glr.c)
+
+ The C parsers were broken when %defines was used together with "%define
+ api.value.type union".
+
+*** Redeclarations are reported in proper order
+
+ On
+
+ %token FOO "foo"
+ %printer {} "foo"
+ %printer {} FOO
+
+ bison used to report:
+
+ /tmp/foo.yy:2.10-11: error: %printer redeclaration for FOO
+ %printer {} "foo"
+ ^^
+ /tmp/foo.yy:3.10-11: previous declaration
+ %printer {} FOO
+ ^^
+
+ Now, the "previous" declaration is always the first one.
+
+
+** Documentation
+
+ Bison now installs various files in its docdir (which defaults to
+ '/usr/local/share/doc/bison'), including the three fully blown examples
+ extracted from the documentation:
+
+ - rpcalc
+ Reverse polish calculator, a simple introductory example.
+ - mfcalc
+ Multi-function Calc, a calculator with memory and functions and located
+ error messages.
+ - calc++
+ a calculator in C++ using variant support and token constructors.
+
+* Noteworthy changes in release 3.0.2 (2013-12-05) [stable]
+
+** Bug fixes
+
+*** Generated source files when errors are reported
+
+ When warnings are issued and -Werror is set, bison would still generate
+ the source files (*.c, *.h...). As a consequence, some runs of "make"
+ could fail the first time, but not the second (as the files were generated
+ anyway).
+
+ This is fixed: bison no longer generates this source files, but, of
+ course, still produces the various reports (*.output, *.xml, etc.).
+
+*** %empty is used in reports
+
+ Empty right-hand sides are denoted by '%empty' in all the reports (text,
+ dot, XML and formats derived from it).
+
+*** YYERROR and variants
+
+ When C++ variant support is enabled, an error triggered via YYERROR, but
+ not caught via error recovery, resulted in a double deletion.
+
+* Noteworthy changes in release 3.0.1 (2013-11-12) [stable]
+
+** Bug fixes
+
+*** Errors in caret diagnostics
+
+ On some platforms, some errors could result in endless diagnostics.
+
+*** Fixes of the -Werror option
+
+ Options such as "-Werror -Wno-error=foo" were still turning "foo"
+ diagnostics into errors instead of warnings. This is fixed.
+
+ Actually, for consistency with GCC, "-Wno-error=foo -Werror" now also
+ leaves "foo" diagnostics as warnings. Similarly, with "-Werror=foo
+ -Wno-error", "foo" diagnostics are now errors.
+
+*** GLR Predicates
+
+ As demonstrated in the documentation, one can now leave spaces between
+ "%?" and its "{".
+
+*** Installation
+
+ The yacc.1 man page is no longer installed if --disable-yacc was
+ specified.
+
+*** Fixes in the test suite
+
+ Bugs and portability issues.
+
+* Noteworthy changes in release 3.0 (2013-07-25) [stable]
+
+** WARNING: Future backward-incompatibilities!
+
+ Like other GNU packages, Bison will start using some of the C99 features
+ for its own code, especially the definition of variables after statements.
+ The generated C parsers still aim at C90.
+
+** Backward incompatible changes
+
+*** Obsolete features
+
+ Support for YYFAIL is removed (deprecated in Bison 2.4.2): use YYERROR.
+
+ Support for yystype and yyltype is removed (deprecated in Bison 1.875):
+ use YYSTYPE and YYLTYPE.
+
+ Support for YYLEX_PARAM and YYPARSE_PARAM is removed (deprecated in Bison
+ 1.875): use %lex-param, %parse-param, or %param.
+
+ Missing semicolons at the end of actions are no longer added (as announced
+ in the release 2.5).
+
+*** Use of YACC='bison -y'
+
+ TL;DR: With Autoconf <= 2.69, pass -Wno-yacc to (AM_)YFLAGS if you use
+ Bison extensions.
+
+ Traditional Yacc generates 'y.tab.c' whatever the name of the input file.
+ Therefore Makefiles written for Yacc expect 'y.tab.c' (and possibly
+ 'y.tab.h' and 'y.outout') to be generated from 'foo.y'.
+
+ To this end, for ages, AC_PROG_YACC, Autoconf's macro to look for an
+ implementation of Yacc, was using Bison as 'bison -y'. While it does
+ ensure compatible output file names, it also enables warnings for
+ incompatibilities with POSIX Yacc. In other words, 'bison -y' triggers
+ warnings for Bison extensions.
+
+ Autoconf 2.70+ fixes this incompatibility by using YACC='bison -o y.tab.c'
+ (which also generates 'y.tab.h' and 'y.output' when needed).
+ Alternatively, disable Yacc warnings by passing '-Wno-yacc' to your Yacc
+ flags (YFLAGS, or AM_YFLAGS with Automake).
+
+** Bug fixes
+
+*** The epilogue is no longer affected by internal #defines (glr.c)
+
+ The glr.c skeleton uses defines such as #define yylval (yystackp->yyval) in
+ generated code. These weren't properly undefined before the inclusion of
+ the user epilogue, so functions such as the following were butchered by the
+ preprocessor expansion:
+
+ int yylex (YYSTYPE *yylval);
+
+ This is fixed: yylval, yynerrs, yychar, and yylloc are now valid
+ identifiers for user-provided variables.
+
+*** stdio.h is no longer needed when locations are enabled (yacc.c)
+
+ Changes in Bison 2.7 introduced a dependency on FILE and fprintf when
+ locations are enabled. This is fixed.
+
+*** Warnings about useless %pure-parser/%define api.pure are restored
+
+** Diagnostics reported by Bison
+
+ Most of these features were contributed by Théophile Ranquet and Victor
+ Santet.
+
+*** Carets
+
+ Version 2.7 introduced caret errors, for a prettier output. These are now
+ activated by default. The old format can still be used by invoking Bison
+ with -fno-caret (or -fnone).
+
+ Some error messages that reproduced excerpts of the grammar are now using
+ the caret information only. For instance on:
+
+ %%
+ exp: 'a' | 'a';
+
+ Bison 2.7 reports:
+
+ in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
+ in.y:2.12-14: warning: rule useless in parser due to conflicts: exp: 'a' [-Wother]
+
+ Now bison reports:
+
+ in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
+ in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother]
+ exp: 'a' | 'a';
+ ^^^
+
+ and "bison -fno-caret" reports:
+
+ in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
+ in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother]
+
+*** 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
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
-** Warnings about undeclared symbols
+*** Undefined but unused symbols
- Bison used to raise an error for %printer and %destructor directives for
- undefined 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";
- This is now only a warning.
-
-** Warnings about useless destructors or printers
+*** 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
%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
+
+** Incompatibilities with POSIX Yacc
+
+ The 'yacc' category is no longer part of '-Wall', enable it explicitly
+ with '-Wyacc'.
+
** Additional yylex/yyparse arguments
The new directive %param declares additional arguments to both yylex and
%param {arg1_type *arg1} {arg2_type *arg2}
-** Java skeleton improvements
+** Types of values for %define variables
- 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".
+ Bison used to make no difference between '%define foo bar' and '%define
+ foo "bar"'. The former is now called a 'keyword value', and the latter a
+ 'string value'. A third kind was added: 'code values', such as '%define
+ foo {bar}'.
-** C++ skeleton improvements
+ Keyword variables are used for fixed value sets, e.g.,
- 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).
+ %define lr.type lalr
-** Variable api.tokens.prefix
+ Code variables are used for value in the target language, e.g.,
- The variable api.tokens.prefix changes the way tokens are identified in
+ %define api.value.type {struct semantic_type}
+
+ String variables are used remaining cases, e.g. file names.
+
+** 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.tokens.prefix "TOK_"
+ %define api.token.prefix {TOK_}
%%
start: FILE for ERROR;
use these prefixed token names, although the grammar itself still
uses the short names (as in the sample rule given above).
-** Variable api.namespace
+** Variable api.value.type
- The "namespace" variable is renamed "api.namespace". Backward
- compatibility is ensured, but upgrading is recommended.
+ This new %define variable supersedes the #define macro YYSTYPE. The use
+ of YYSTYPE is discouraged. In particular, #defining YYSTYPE *and* either
+ using %union or %defining api.value.type results in undefined behavior.
+
+ Either define api.value.type, or use "%union":
+
+ %union
+ {
+ int ival;
+ char *sval;
+ }
+ %token <ival> INT "integer"
+ %token <sval> STRING "string"
+ %printer { fprintf (yyo, "%d", $$); } <ival>
+ %destructor { free ($$); } <sval>
+
+ /* In yylex(). */
+ yylval.ival = 42; return INT;
+ yylval.sval = "42"; return STRING;
+
+ The %define variable api.value.type supports both keyword and code values.
+
+ The keyword value 'union' means that the user provides genuine types, not
+ union member names such as "ival" and "sval" above (WARNING: will fail if
+ -y/--yacc/%yacc is enabled).
+
+ %define api.value.type union
+ %token <int> INT "integer"
+ %token <char *> STRING "string"
+ %printer { fprintf (yyo, "%d", $$); } <int>
+ %destructor { free ($$); } <char *>
+
+ /* In yylex(). */
+ yylval.INT = 42; return INT;
+ yylval.STRING = "42"; return STRING;
+
+ The keyword value variant is somewhat equivalent, but for C++ special
+ provision is made to allow classes to be used (more about this below).
+
+ %define api.value.type variant
+ %token <int> INT "integer"
+ %token <std::string> STRING "string"
+
+ Code values (in braces) denote user defined types. This is where YYSTYPE
+ used to be used.
+
+ %code requires
+ {
+ struct my_value
+ {
+ enum
+ {
+ is_int, is_string
+ } kind;
+ union
+ {
+ int ival;
+ char *sval;
+ } u;
+ };
+ }
+ %define api.value.type {struct my_value}
+ %token <u.ival> INT "integer"
+ %token <u.sval> STRING "string"
+ %printer { fprintf (yyo, "%d", $$); } <u.ival>
+ %destructor { free ($$); } <u.sval>
+
+ /* In yylex(). */
+ yylval.u.ival = 42; return INT;
+ yylval.u.sval = "42"; return STRING;
** Variable parse.error
- The variable error controls the verbosity of error messages. The
- use of the %error-verbose directive is deprecated in favor of
- %define parse.error "verbose".
+ This variable controls the verbosity of error messages. The use of the
+ %error-verbose directive is deprecated in favor of "%define parse.error
+ verbose".
+
+** 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
+ stype -> api.value.type
** Semantic predicates
- The new, experimental, semantic-predicate feature allows actions of
- the form %?{ BOOLEAN-EXPRESSION }, which cause syntax errors (as for
+ Contributed by Paul Hilfinger.
+
+ 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.
+ 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.
-* Noteworthy changes in release ?.? (????-??-??) [?]
+** 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.
+
+** Tokens are numbered in their order of appearance
+
+ Contributed by Valentin Tolmer.
+
+ With '%token A B', A had a number less than the one of B. However,
+ precedence declarations used to generate a reversed order. This is now
+ fixed, and introducing tokens with any of %token, %left, %right,
+ %precedence, or %nonassoc yields the same result.
+
+ When mixing declarations of tokens with a litteral character (e.g., 'a')
+ or with an identifier (e.g., B) in a precedence declaration, Bison
+ numbered the litteral characters first. For example
+
+ %right A B 'c' 'd'
+
+ would lead to the tokens declared in this order: 'c' 'd' A B. Again, the
+ input order is now preserved.
+
+ These changes were made so that one can remove useless precedence and
+ associativity declarations (i.e., map %nonassoc, %left or %right to
+ %precedence, or to %token) and get exactly the same output.
+
+** Useless precedence and associativity
+
+ Contributed by Valentin Tolmer.
+
+ When developing and maintaining a grammar, useless associativity and
+ precedence directives are common. They can be a nuisance: new ambiguities
+ arising are sometimes masked because their conflicts are resolved due to
+ the extra precedence or associativity information. Furthermore, it can
+ hinder the comprehension of a new grammar: one will wonder about the role
+ of a precedence, where in fact it is useless. The following changes aim
+ at detecting and reporting these extra directives.
+
+*** Precedence warning category
+
+ A new category of warning, -Wprecedence, was introduced. It flags the
+ useless precedence and associativity directives.
+
+*** Useless associativity
+
+ Bison now warns about symbols with a declared associativity that is never
+ used to resolve conflicts. In that case, using %precedence is sufficient;
+ the parsing tables will remain unchanged. Solving these warnings may raise
+ useless precedence warnings, as the symbols no longer have associativity.
+ For example:
+
+ %left '+'
+ %left '*'
+ %%
+ exp:
+ "number"
+ | exp '+' "number"
+ | exp '*' exp
+ ;
+
+ will produce a
+
+ warning: useless associativity for '+', use %precedence [-Wprecedence]
+ %left '+'
+ ^^^
+
+*** Useless precedence
+
+ Bison now warns about symbols with a declared precedence and no declared
+ associativity (i.e., declared with %precedence), and whose precedence is
+ never used. In that case, the symbol can be safely declared with %token
+ instead, without modifying the parsing tables. For example:
+
+ %precedence '='
+ %%
+ exp: "var" '=' "number";
+
+ will produce a
+
+ warning: useless precedence for '=' [-Wprecedence]
+ %precedence '='
+ ^^^
+
+*** Useless precedence and associativity
+
+ In case of both useless precedence and associativity, the issue is flagged
+ as follows:
+
+ %nonassoc '='
+ %%
+ exp: "var" '=' "number";
+
+ The warning is:
+
+ warning: useless precedence and associativity for '=' [-Wprecedence]
+ %nonassoc '='
+ ^^^
+
+** Empty rules
+
+ With help from Joel E. Denny and Gabriel Rassoul.
+
+ Empty rules (i.e., with an empty right-hand side) can now be explicitly
+ marked by the new %empty directive. Using %empty on a non-empty rule is
+ an error. The new -Wempty-rule warning reports empty rules without
+ %empty. On the following grammar:
+
+ %%
+ s: a b c;
+ a: ;
+ b: %empty;
+ c: 'a' %empty;
+
+ bison reports:
+
+ 3.4-5: warning: empty rule without %empty [-Wempty-rule]
+ a: {}
+ ^^
+ 5.8-13: error: %empty on non-empty rule
+ c: 'a' %empty {};
+ ^^^^^^
+
+** 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".
+ Contributed by Paolo Bonzini.
+
+ The Java skeleton now supports push parsing.
+ Contributed by Dennis Heimbigner.
+
+** 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).
+
+*** %define api.value.type variant
+
+ This is based on a submission from Michiel De Wilde. With help
+ from Théophile Ranquet.
+
+ In this mode, complex C++ objects can be used as semantic values. For
+ instance:
+
+ %token <::std::string> TEXT;
+ %token <int> NUMBER;
+ %token SEMICOLON ";"
+ %type <::std::string> item;
+ %type <::std::list<std::string>> list;
+ %%
+ result:
+ list { std::cout << $1 << std::endl; }
+ ;
+
+ list:
+ %empty { /* Generates an empty string list. */ }
+ | list item ";" { std::swap ($$, $1); $$.push_back ($2); }
+ ;
+
+ item:
+ TEXT { std::swap ($$, $1); }
+ | NUMBER { $$ = string_cast ($1); }
+ ;
+
+*** %define api.token.constructor
+
+ When variants are enabled, Bison can generate functions to build the
+ tokens. This guarantees that the token type (e.g., NUMBER) is consistent
+ with the semantic value (e.g., int):
+
+ parser::symbol_type yylex ()
+ {
+ parser::location_type loc = ...;
+ ...
+ return parser::make_TEXT ("Hello, world!", loc);
+ ...
+ return parser::make_NUMBER (42, loc);
+ ...
+ return parser::make_SEMICOLON (loc);
+ ...
+ }
+
+*** C++ locations
+
+ There are operator- and operator-= for 'location'. Negative line/column
+ increments can no longer underflow the resulting value.
+
+* Noteworthy changes in release 2.7.1 (2013-04-15) [stable]
+
+** Bug fixes
+
+*** Fix compiler attribute portability (yacc.c)
+
+ With locations enabled, __attribute__ was used unprotected.
+
+*** Fix some compiler warnings (lalr1.cc)
+
+* Noteworthy changes in release 2.7 (2012-12-12) [stable]
+
+** Bug fixes
+
+ Warnings about uninitialized yylloc in yyparse have been fixed.
+
+ Restored C90 compliance (yet no report was ever made).
+
+** Diagnostics are improved
+
+ Contributed by Théophile Ranquet.
+
+*** Changes in the format of error messages
+
+ This used to be the format of many error reports:
+
+ input.y:2.7-12: %type redeclaration for exp
+ input.y:1.7-12: previous declaration
+
+ It is now:
+
+ input.y:2.7-12: error: %type redeclaration for exp
+ input.y:1.7-12: previous declaration
+
+*** New format for error reports: carets
+
+ Caret errors have been added to Bison:
+
+ input.y:2.7-12: error: %type redeclaration for exp
+ %type <sval> exp
+ ^^^^^^
+ input.y:1.7-12: previous declaration
+ %type <ival> exp
+ ^^^^^^
+
+ or
+
+ input.y:3.20-23: error: ambiguous reference: '$exp'
+ exp: exp '+' exp { $exp = $1 + $3; };
+ ^^^^
+ input.y:3.1-3: refers to: $exp at $$
+ exp: exp '+' exp { $exp = $1 + $3; };
+ ^^^
+ input.y:3.6-8: refers to: $exp at $1
+ exp: exp '+' exp { $exp = $1 + $3; };
+ ^^^
+ input.y:3.14-16: refers to: $exp at $3
+ exp: exp '+' exp { $exp = $1 + $3; };
+ ^^^
+
+ The default behavior for now is still not to display these unless
+ explicitly asked with -fcaret (or -fall). However, in a later release, it
+ will be made the default behavior (but may still be deactivated with
+ -fno-caret).
+
+** 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 a 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".
+
+** New %define variable: api.location.type (glr.cc, lalr1.cc, lalr1.java)
+
+ The %define variable api.location.type defines the name of the type to use
+ for locations. When defined, Bison no longer generates the position.hh
+ and location.hh files, nor does the parser will include them: the user is
+ then responsible to define her type.
+
+ This can be used in programs with several parsers to factor their location
+ and position files: let one of them generate them, and the others just use
+ them.
+
+ This feature was actually introduced, but not documented, in Bison 2.5,
+ under the name "location_type" (which is maintained for backward
+ compatibility).
+
+ For consistency, lalr1.java's %define variables location_type and
+ position_type are deprecated in favor of api.location.type and
+ api.position.type.
+
+** Exception safety (lalr1.cc)
+
+ The parse function now catches exceptions, uses the %destructors to
+ release memory (the lookahead symbol and the symbols pushed on the stack)
+ before re-throwing the exception.
+
+ This feature is somewhat experimental. User feedback would be
+ appreciated.
+
+** Graph improvements in DOT and XSLT
+
+ Contributed by Théophile Ranquet.
+
+ The graphical presentation of the states is more readable: their shape is
+ now rectangular, the state number is clearly displayed, and the items are
+ numbered and left-justified.
+
+ The reductions are now explicitly represented as transitions to other
+ diamond shaped nodes.
+
+ These changes are present in both --graph output and xml2dot.xsl XSLT
+ processing, with minor (documented) differences.
+
+** %language is no longer an experimental feature.
+
+ The introduction of this feature, in 2.4, was four years ago. The
+ --language option and the %language directive are no longer experimental.
+
+** Documentation
+
+ The sections about shift/reduce and reduce/reduce conflicts resolution
+ have been fixed and extended.
+
+ Although introduced more than four years ago, XML and Graphviz reports
+ were not properly documented.
+
+ The translation of mid-rule actions is now described.
+
+* Noteworthy changes in release 2.6.5 (2012-11-07) [stable]
+
+ We consider compiler warnings about Bison generated parsers to be bugs.
+ Rather than working around them in your own project, please consider
+ reporting them to us.
+
+** Bug fixes
+
+ Warnings about uninitialized yylval and/or yylloc for push parsers with a
+ pure interface have been fixed for GCC 4.0 up to 4.8, and Clang 2.9 to
+ 3.2.
+
+ Other issues in the test suite have been addressed.
+
+ Null characters are correctly displayed in error messages.
+
+ When possible, yylloc is correctly initialized before calling yylex. It
+ is no longer necessary to initialize it in the %initial-action.
+
+* Noteworthy changes in release 2.6.4 (2012-10-23) [stable]
+
+ Bison 2.6.3's --version was incorrect. This release fixes this issue.
+
+* Noteworthy changes in release 2.6.3 (2012-10-22) [stable]
+
+** Bug fixes
+
+ Bugs and portability issues in the test suite have been fixed.
+
+ Some errors in translations have been addressed, and --help now directs
+ users to the appropriate place to report them.
+
+ Stray Info files shipped by accident are removed.
+
+ Incorrect definitions of YY_, issued by yacc.c when no parser header is
+ generated, are removed.
+
+ All the generated headers are self-contained.
+
+** Header guards (yacc.c, glr.c, glr.cc)
+
+ In order to avoid collisions, the header guards are now
+ YY_<PREFIX>_<FILE>_INCLUDED, instead of merely <PREFIX>_<FILE>.
+ For instance the header generated from
+
+ %define api.prefix "calc"
+ %defines "lib/parse.h"
+
+ will use YY_CALC_LIB_PARSE_H_INCLUDED as guard.
+
+** Fix compiler warnings in the generated parser (yacc.c, glr.c)
+
+ The compilation of pure parsers (%define api.pure) can trigger GCC
+ warnings such as:
+
+ input.c: In function 'yyparse':
+ input.c:1503:12: warning: 'yylval' may be used uninitialized in this
+ function [-Wmaybe-uninitialized]
+ *++yyvsp = yylval;
+ ^
+
+ This is now fixed; pragmas to avoid these warnings are no longer needed.
+
+ Warnings from clang ("equality comparison with extraneous parentheses" and
+ "function declared 'noreturn' should not return") have also been
+ addressed.
+
+* Noteworthy changes in release 2.6.2 (2012-08-03) [stable]
+
+** Bug fixes
+
+ Buffer overruns, complaints from Flex, and portability issues in the test
+ suite have been fixed.
+
+** Spaces in %lex- and %parse-param (lalr1.cc, glr.cc)
+
+ Trailing end-of-lines in %parse-param or %lex-param would result in
+ invalid C++. This is fixed.
+
+** Spurious spaces and end-of-lines
+
+ The generated files no longer end (nor start) with empty lines.
+
+* Noteworthy changes in release 2.6.1 (2012-07-30) [stable]
+
+ Bison no longer executes user-specified M4 code when processing a grammar.
+
+** Future Changes
+
+ In addition to the removal of the features announced in Bison 2.6, the
+ next major release will remove the "Temporary hack for adding a semicolon
+ to the user action", as announced in the release 2.5. Instead of:
+
+ exp: exp "+" exp { $$ = $1 + $3 };
+
+ write:
+
+ exp: exp "+" exp { $$ = $1 + $3; };
+
+** Bug fixes
+
+*** Type names are now properly escaped.
+
+*** glr.cc: set_debug_level and debug_level work as expected.
+
+*** Stray @ or $ in actions
+
+ While Bison used to warn about stray $ or @ in action rules, it did not
+ for other actions such as printers, destructors, or initial actions. It
+ now does.
+
+** Type names in actions
+
+ For consistency with rule actions, it is now possible to qualify $$ by a
+ type-name in destructors, printers, and initial actions. For instance:
+
+ %printer { fprintf (yyo, "(%d, %f)", $<ival>$, $<fval>$); } <*> <>;
+
+ will display two values for each typed and untyped symbol (provided
+ that YYSTYPE has both "ival" and "fval" fields).
+
+* Noteworthy changes in release 2.6 (2012-07-19) [stable]
** Future changes
The next major release of Bison will drop support for the following
deprecated features. Please report disagreements to bug-bison@gnu.org.
-*** K&C parsers
+*** K&R C parsers
Support for generating parsers in K&R C will be removed. Parsers
- generated for C supprt ISO C90, and are tested with ISO C99 and ISO C11
+ generated for C support ISO C90, and are tested with ISO C99 and ISO C11
compilers.
-*** Deprecated features
+*** Features deprecated since Bison 1.875
+
+ The definitions of yystype and yyltype will be removed; use YYSTYPE and
+ YYLTYPE.
- The definitions of yystype and yyltype will be removed, as announced since
- Bison 1.875. Use YYSTYPE and YYLTYPE only.
+ YYPARSE_PARAM and YYLEX_PARAM, deprecated in favor of %parse-param and
+ %lex-param, will no longer be supported.
- YYPARSE_PARAM and YYLEX_PARAM, which were deprecated in favor of
- %parse-param and %lex-param (introduced in Bison 1.875), will no longer be
- supported.
+ Support for the preprocessor symbol YYERROR_VERBOSE will be removed, use
+ %error-verbose.
*** The generated header will be included (yacc.c)
because existing versions of ylwrap (e.g., Automake 1.12.1) do not support
it.
-** Headers (yacc.c, glr.c, glr.cc)
+** Generated Parser Headers
-*** Guards
+*** Guards (yacc.c, glr.c, glr.cc)
The generated headers are now guarded, as is already the case for C++
- parsers (lalr1.cc). For intance, with --defines=foo.h:
+ parsers (lalr1.cc). For instance, with --defines=foo.h:
#ifndef YY_FOO_H
# define YY_FOO_H
...
#endif /* !YY_FOO_H */
-*** New declarations
+*** New declarations (yacc.c, glr.c)
The generated header now declares yydebug and yyparse. Both honor
--name-prefix=bar_, and yield
in order to facilitate the inclusion of several parser headers inside a
single compilation unit.
+*** Exported symbols in C++
+
+ The symbols YYTOKEN_TABLE and YYERROR_VERBOSE, which were defined in the
+ header, are removed, as they prevent the possibility of including several
+ generated headers from a single compilation unit.
+
+*** YYLSP_NEEDED
+
+ For the same reasons, the undocumented and unused macro YYLSP_NEEDED is no
+ longer defined.
+
+** New %define variable: api.prefix
+
+ Now that the generated headers are more complete and properly protected
+ against multiple inclusions, constant names, such as YYSTYPE are a
+ problem. While yyparse and others are properly renamed by %name-prefix,
+ YYSTYPE, YYDEBUG and others have never been affected by it. Because it
+ would introduce backward compatibility issues in projects not expecting
+ YYSTYPE to be renamed, instead of changing the behavior of %name-prefix,
+ it is deprecated in favor of a new %define variable: api.prefix.
+
+ The following examples compares both:
+
+ %name-prefix "bar_" | %define api.prefix "bar_"
+ %token <ival> FOO %token <ival> FOO
+ %union { int ival; } %union { int ival; }
+ %% %%
+ exp: 'a'; exp: 'a';
+
+ bison generates:
+
+ #ifndef BAR_FOO_H #ifndef BAR_FOO_H
+ # define BAR_FOO_H # define BAR_FOO_H
+
+ /* Enabling traces. */ /* Enabling traces. */
+ # ifndef YYDEBUG | # ifndef BAR_DEBUG
+ > # if defined YYDEBUG
+ > # if YYDEBUG
+ > # define BAR_DEBUG 1
+ > # else
+ > # define BAR_DEBUG 0
+ > # endif
+ > # else
+ # define YYDEBUG 0 | # define BAR_DEBUG 0
+ > # endif
+ # endif | # endif
+
+ # if YYDEBUG | # if BAR_DEBUG
+ extern int bar_debug; extern int bar_debug;
+ # endif # endif
+
+ /* Tokens. */ /* Tokens. */
+ # ifndef YYTOKENTYPE | # ifndef BAR_TOKENTYPE
+ # define YYTOKENTYPE | # define BAR_TOKENTYPE
+ enum yytokentype { | enum bar_tokentype {
+ FOO = 258 FOO = 258
+ }; };
+ # endif # endif
+
+ #if ! defined YYSTYPE \ | #if ! defined BAR_STYPE \
+ && ! defined YYSTYPE_IS_DECLARED | && ! defined BAR_STYPE_IS_DECLARED
+ typedef union YYSTYPE | typedef union BAR_STYPE
+ { {
+ int ival; int ival;
+ } YYSTYPE; | } BAR_STYPE;
+ # define YYSTYPE_IS_DECLARED 1 | # define BAR_STYPE_IS_DECLARED 1
+ #endif #endif
+
+ extern YYSTYPE bar_lval; | extern BAR_STYPE bar_lval;
+
+ int bar_parse (void); int bar_parse (void);
+
+ #endif /* !BAR_FOO_H */ #endif /* !BAR_FOO_H */
+
* Noteworthy changes in release 2.5.1 (2012-06-05) [stable]
** Future changes:
These features are experimental in this version. More user feedback
will help to stabilize them.
+ Contributed by Alex Rozenman.
** IELR(1) and canonical LR(1):
These features are experimental. More user feedback will help to
stabilize them.
-** LAC (Lookahead Correction) for syntax error handling:
+** LAC (Lookahead Correction) for syntax error handling
+
+ Contributed by Joel E. Denny.
Canonical LR, IELR, and LALR can suffer from a couple of problems
upon encountering a syntax error. First, the parser might perform
The current Java interface is experimental and may evolve. More user
feedback will help to stabilize it.
+ Contributed by Paolo Bonzini.
** %language
Bison can now generate an XML report of the LALR(1) automaton using the new
"--xml" option. The current XML schema is experimental and may evolve. More
user feedback will help to stabilize it.
+ Contributed by Wojciech Polak.
** The grammar file may now specify the name of the parser header file using
%defines. For example:
- a single argument only can be added,
- their types are weak (void *),
- - this context is not passed to anciliary functions such as yyerror,
+ - this context is not passed to ancillary functions such as yyerror,
- only yacc.c parsers support them.
The new %parse-param/%lex-param directives provide a more precise control.
-----
-Copyright (C) 1995-2012 Free Software Foundation, Inc.
+Copyright (C) 1995-2015 Free Software Foundation, Inc.
This file is part of Bison, the GNU Parser Generator.
LocalWords: struct yystype DJGPP lex param Haible NUM alloca YYSTACK NUL goto
LocalWords: YYMAXDEPTH Unescaped UCNs YYLTYPE's yyltype typedefs inline Yaccs
LocalWords: Heriyanto Reenable dprec Hilfinger Eggert MYEOF Folle Menezes EOF
- LocalWords: Lackovic define's itemset Groff Gettext malloc NEWS'ed YYDEBUG
+ LocalWords: Lackovic define's itemset Groff Gettext malloc NEWS'ed YYDEBUG YY
LocalWords: namespaces strerror const autoconfiguration Dconst Autoconf's FDL
- LocalWords: Automake TMPDIR LESSEQ
+ LocalWords: Automake TMPDIR LESSEQ ylwrap endif yydebug YYTOKEN YYLSP ival hh
+ LocalWords: extern YYTOKENTYPE TOKENTYPE yytokentype tokentype STYPE lval pdf
+ LocalWords: lang yyoutput dvi html ps POSIX lvalp llocp Wother nterm arg init
+ LocalWords: TOK calc yyo fval Wconflicts parsers yystackp yyval yynerrs
+ LocalWords: Théophile Ranquet Santet fno fnone stype associativity Tolmer
+ LocalWords: Wprecedence Rassoul Wempty Paolo Bonzini parser's Michiel loc
+ LocalWords: redeclaration sval fcaret reentrant XSLT xsl Wmaybe yyvsp Tedi
+ LocalWords: pragmas noreturn untyped Rozenman unexpanded Wojciech Polak
+ LocalWords: Alexandre MERCHANTABILITY yytype
Local Variables:
mode: outline
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