X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/e29f0771d7a7a569f830bfe75216e1e0db3362e4..9641b918bae9eb8d0bb9099ab6d9d46383ba8bc9:/NEWS diff --git a/NEWS b/NEWS index 9c5d67b7..96a5deb1 100644 --- a/NEWS +++ b/NEWS @@ -2,11 +2,110 @@ 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. + +** 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++ skeleton improvements + + 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.tokens.prefix + + The variable api.tokens.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_" + %% + 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). + +** Variable api.namespace + + The "namespace" variable is renamed "api.namespace". Backward + compatibility is ensured, but upgrading is recommended. + +** 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". + +** 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 + runtime expressions. + +* Noteworthy changes in release ?.? (????-??-??) [?] + ** Future changes: The next major release will drop support for generating parsers in K&R C, - and remove the definition of yystype (removal announced since Bison - 1.875). + and remove the definitions of yystype and yyltype (removal announced since + Bison 1.875). YYPARSE_PARAM and YYLEX_PARAM, which were deprecated in + favor of %parse-param and %lex-param (introduced in Bison 1.875 too), will + no longer be supported. ** The generated header is included (yacc.c) @@ -78,10 +177,10 @@ 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 @@ -89,10 +188,10 @@ 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: @@ -323,33 +422,33 @@ 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++: @@ -1202,6 +1301,33 @@ 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. @@ -1322,9 +1448,9 @@ 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. @@ -1343,9 +1469,9 @@ 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. @@ -1381,9 +1507,9 @@ 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.