* Noteworthy changes in release ?.? (????-??-??) [?]
+** Warnings about 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
+
+** Warnings about undeclared symbols
+
+ Bison used to raise an error for %printer and %destructor directives for
+ undefined symbols.
+
+ %printer {} symbol1
+ %destructor {} symbol2
+ %%
+ exp: "a";
+
+ This is now only a warning.
+
+** Warnings about 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>
+
** Additional yylex/yyparse arguments
- The new directive %param declare additional argument to both yylex
- and yyparse. The %lex-param, %parse-param, and %param directives
- support one or more arguments. Instead of
+ 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}
+ %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}
+ %param {arg1_type *arg1} {arg2_type *arg2}
** Java skeleton improvements
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_"
- %%
- start: FILE for ERROR;
+ %token FILE for ERROR
+ %define api.tokens.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
allow the programmer to prune possible parses based on the values of
runtime expressions.
+* Noteworthy changes in release ?.? (????-??-??) [?]
+
+** 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
+
+ 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
+ compilers.
+
+*** Features deprecated since Bison 1.875
+
+ The definitions of yystype and yyltype will be removed; use YYSTYPE and
+ YYLTYPE.
+
+ YYPARSE_PARAM and YYLEX_PARAM, deprecated in favor of %parse-param and
+ %lex-param, 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)
+
+ Instead of duplicating the content of the generated header (definition of
+ YYSTYPE, yyparse declaration etc.), the generated parser will include it,
+ as is already the case for GLR or C++ parsers. This change is deferred
+ because existing versions of ylwrap (e.g., Automake 1.12.1) do not support
+ it.
+
+** Headers
+
+*** 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:
+
+ #ifndef YY_FOO_H
+ # define YY_FOO_H
+ ...
+ #endif /* !YY_FOO_H */
+
+*** New declarations (yacc.c, glr.c)
+
+ The generated header now declares yydebug and yyparse. Both honor
+ --name-prefix=bar_, and yield
+
+ int bar_parse (void);
+
+ rather than
+
+ #define yyparse bar_parse
+ int yyparse (void);
+
+ 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.
+
* Noteworthy changes in release 2.5.1 (2012-06-05) [stable]
** Future changes:
The header files such as "parser.hh", "location.hh", etc. used a constant
name for preprocessor guards, for instance:
- #ifndef BISON_LOCATION_HH
- # define BISON_LOCATION_HH
- ...
- #endif // !BISON_LOCATION_HH
+ #ifndef BISON_LOCATION_HH
+ # define BISON_LOCATION_HH
+ ...
+ #endif // !BISON_LOCATION_HH
The inclusion guard is now computed from "PREFIX/FILE-NAME", where lower
case characters are converted to upper case, and series of
With "bison -o lang++/parser.cc", "location.hh" would now include:
- #ifndef YY_LANG_LOCATION_HH
- # define YY_LANG_LOCATION_HH
- ...
- #endif // !YY_LANG_LOCATION_HH
+ #ifndef YY_LANG_LOCATION_HH
+ # define YY_LANG_LOCATION_HH
+ ...
+ #endif // !YY_LANG_LOCATION_HH
*** C++ locations:
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)
+ # 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)
+ # 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++:
- "parsing stack overflow..." -> "parser stack overflow"
GLR parsers now report "parser stack overflow" as per the Bison manual.
+** %parse-param and %lex-param
+ The macros YYPARSE_PARAM and YYLEX_PARAM provide a means to pass
+ additional context to yyparse and yylex. They suffer from several
+ shortcomings:
+
+ - a single argument only can be added,
+ - their types are weak (void *),
+ - this context is not passed to anciliary functions such as yyerror,
+ - only yacc.c parsers support them.
+
+ The new %parse-param/%lex-param directives provide a more precise control.
+ For instance:
+
+ %parse-param {int *nastiness}
+ %lex-param {int *nastiness}
+ %parse-param {int *randomness}
+
+ results in the following signatures:
+
+ int yylex (int *nastiness);
+ int yyparse (int *nastiness, int *randomness);
+
+ or, if both %pure-parser and %locations are used:
+
+ int yylex (YYSTYPE *lvalp, YYLTYPE *llocp, int *nastiness);
+ int yyparse (int *nastiness, int *randomness);
+
** Bison now warns if it detects conflicting outputs to the same file,
e.g., it generates a warning for "bison -d -o foo.h foo.y" since
that command outputs both code and header to foo.h.
** Incorrect "Token not used"
On a grammar such as
- %token useless useful
- %%
- exp: '0' %prec useful;
+ %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.
the user symbol is used in the reports, the graphs, and the verbose
error messages instead of "$end", which remains being the default.
For instance
- %token MYEOF 0
+ %token MYEOF 0
or
- %token MYEOF 0 "end of file"
+ %token MYEOF 0 "end of file"
** Semantic parser
This old option, which has been broken for ages, is removed.
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';
+ %type <foo> bar
+ %%
+ bar: '0' {} '0';
This is fixed.
projects / bison.git / blobdiff