X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/9ce27ab013185d1c17c78e0d57ff637319cb1e29..7aaaad6c6dc0fae412d608dcf20a3977d8902cd1:/NEWS diff --git a/NEWS b/NEWS index 79fdb8ef..e1373657 100644 --- a/NEWS +++ b/NEWS @@ -2,20 +2,63 @@ GNU Bison NEWS * 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 term + %type nterm + %printer {} + %destructor {} + %% + nterm: term { $$ = $1; }; + + 3.28-34: warning: type is used, but is not associated to any symbol + 4.28-34: warning: type 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 , and the destructor for are + useless: all symbols of (token1) already have a printer, and all + symbols of type (token2) already have a destructor. + + %token token1 + token2 + token3 + token4 + %printer {} token1 + %destructor {} token2 + ** 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 @@ -38,10 +81,10 @@ GNU Bison NEWS 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 @@ -68,6 +111,76 @@ GNU Bison NEWS 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: @@ -105,10 +218,10 @@ GNU Bison NEWS 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 @@ -116,10 +229,10 @@ GNU Bison NEWS 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: @@ -350,33 +463,33 @@ GNU Bison NEWS 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++: @@ -1229,6 +1342,33 @@ GNU Bison NEWS - "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. @@ -1349,9 +1489,9 @@ GNU Bison NEWS ** 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. @@ -1370,9 +1510,9 @@ GNU Bison NEWS 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. @@ -1408,9 +1548,9 @@ GNU Bison NEWS 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 bar - %% - bar: '0' {} '0'; + %type bar + %% + bar: '0' {} '0'; This is fixed.