X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/c7fb0b9079c70dd906bf180d5eff5d1b65ec73c3..31b2b07ef765e9e8734ca273308094804fcc9763:/NEWS diff --git a/NEWS b/NEWS index 9523191d..d841db6f 100644 --- a/NEWS +++ b/NEWS @@ -1,10 +1,166 @@ Bison News ---------- -Changes in version 2.1a: +Changes in version 2.3+: + +* Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with `-y', + `--yacc', or `%yacc'), Bison no longer generates #define statements for + associating token numbers with token names. Removing the #define statements + helps to sanitize the global namespace during preprocessing, but POSIX Yacc + requires them. Bison still generates an enum for token names in all cases. + +* Handling of prologue blocks is now more consistent but potentially backward + incompatible. + + As before, you declare prologue blocks in your grammar file with the + `%{ ... %}' syntax. To generate the pre-prologue, Bison concatenates all + prologue blocks that you've declared before any %union. If you've declared a + %union, Bison concatenates all prologue blocks that you've declared after it + to generate the post-prologue. (The new %before-definitions and + %after-definitions have a similar effect as %union on the prologues. See + below.) + + Previous versions of Bison inserted the pre-prologue into both the header + file and the code file in all cases except for LALR(1) parsers in C. In the + latter case, Bison inserted it only into the code file. For parsers in C++, + the point of insertion was before any token definitions (which associate + token numbers with names). For parsers in C, the point of insertion was + after the token definitions. + + Now, Bison never inserts the pre-prologue into the header file. In the code + file, it always inserts it before the token definitions. + +* Bison now provides the %before-definitions and %after-definitions directives. + + For example, in your grammar file: + + %{ + /* A pre-prologue block. For Yacc portability, Bison no longer puts this + * in the header file. In the code file, Bison inserts it before any + * %before-definitions blocks. */ + %} + %before-definitions { + /* Bison inserts this into both the header file and code file. In both + * files, the point of insertion is before any Bison-generated token, + * semantic type, location type, and class definitions. This is a good + * place to define %union dependencies, for example. */ + } + %union { + /* With previous versions of Bison, the first %union in your grammar file + * separated the pre-prologue blocks from the post-prologue blocks. Now, + * the first %union, %before-definitions, or %after-definitions does + * that. */ + } + %after-definitions { + /* If you want something in the header file and in the code file and it + * depends on any of the Bison-generated definitions in the header file, + * put it here. */ + } + %{ + /* A post-prologue block. If you want something in the code file but not + * in the header file and it depends on Bison-generated definitions, put + * it here. In the code file, Bison inserts it after any + * %after-definitions blocks. */ + %} + +* The option `--report=look-ahead' has been changed to `--report=lookahead'. + The old spelling still works, but is not documented and may be removed + in a future release. + +Changes in version 2.3, 2006-06-05: + +* GLR grammars should now use `YYRECOVERING ()' instead of `YYRECOVERING', + for compatibility with LALR(1) grammars. + +* It is now documented that any definition of YYSTYPE or YYLTYPE should + be to a type name that does not contain parentheses or brackets. + +Changes in version 2.2, 2006-05-19: + +* The distribution terms for all Bison-generated parsers now permit + using the parsers in nonfree programs. Previously, this permission + was granted only for Bison-generated LALR(1) parsers in C. + +* %name-prefix changes the namespace name in C++ outputs. + +* The C++ parsers export their token_type. + +* Bison now allows multiple %union declarations, and concatenates + their contents together. + +* New warning: unused values + Right-hand side symbols whose values are not used are reported, + if the symbols have destructors. For instance: + + exp: exp "?" exp ":" exp { $1 ? $1 : $3; } + | exp "+" exp + ; + + will trigger a warning about $$ and $5 in the first rule, and $3 in + the second ($1 is copied to $$ by the default rule). This example + most likely contains three errors, and could be rewritten as: + + exp: exp "?" exp ":" exp + { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); } + | exp "+" exp + { $$ = $1 ? $1 : $3; if ($1) free ($3); } + ; + + However, if the original actions were really intended, memory leaks + and all, the warnings can be suppressed by letting Bison believe the + values are used, e.g.: + + exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); } + | exp "+" exp { $$ = $1; (void) $3; } + ; + + If there are mid-rule actions, the warning is issued if no action + uses it. The following triggers no warning: $1 and $3 are used. + + exp: exp { push ($1); } '+' exp { push ($3); sum (); }; + + The warning is intended to help catching lost values and memory leaks. + If a value is ignored, its associated memory typically is not reclaimed. + +* %destructor vs. YYABORT, YYACCEPT, and YYERROR. + Destructors are now called when user code invokes YYABORT, YYACCEPT, + and YYERROR, for all objects on the stack, other than objects + corresponding to the right-hand side of the current rule. + +* %expect, %expect-rr + Incorrect numbers of expected conflicts are now actual errors, + instead of warnings. + +* GLR, YACC parsers. + The %parse-params are available in the destructors (and the + experimental printers) as per the documentation. + +* Bison now warns if it finds a stray `$' or `@' in an action. + +* %require "VERSION" + This specifies that the grammar file depends on features implemented + in Bison version VERSION or higher. + +* lalr1.cc: The token and value types are now class members. + The tokens were defined as free form enums and cpp macros. YYSTYPE + was defined as a free form union. They are now class members: + tokens are enumerations of the `yy::parser::token' struct, and the + semantic values have the `yy::parser::semantic_type' type. + If you do not want or can update to this scheme, the directive + `%define "global_tokens_and_yystype" "1"' triggers the global + definition of tokens and YYSTYPE. This change is suitable both + for previous releases of Bison, and this one. + + If you wish to update, then make sure older version of Bison will + fail using `%require "2.2"'. + +* DJGPP support added. + Changes in version 2.1, 2005-09-16: +* The C++ lalr1.cc skeleton supports %lex-param. + * Bison-generated parsers now support the translation of diagnostics like "syntax error" into languages other than English. The default language is still English. For details, please see the new @@ -26,7 +182,7 @@ Changes in version 2.1, 2005-09-16: a syntax error associated with '%token NUM "number"' they might print 'syntax error, unexpected number' instead of 'syntax error, unexpected "number"'. - + Changes in version 2.0, 2004-12-25: * Possibly-incompatible changes @@ -69,8 +225,7 @@ Changes in version 2.0, 2004-12-25: This is a GNU extension. - The option `--report=lookahead' was changed to `--report=look-ahead'. - The old spelling still works, but is not documented and will be - removed. + [However, this was changed back after 2.3.] - Experimental %destructor support has been added to lalr1.cc. @@ -337,8 +492,8 @@ Changes in version 1.50, 2002-10-04: produces additional information: - itemset complete the core item sets with their closure - - lookahead [changed to `look-ahead' in 1.875e and later] - explicitly associate look-ahead tokens to items + - lookahead [changed to `look-ahead' in 1.875e through 2.3, but changed back] + explicitly associate lookahead tokens to items - solved describe shift/reduce conflicts solving. Bison used to systematically output this information on top of @@ -621,8 +776,8 @@ End: ----- -Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 -Free Software Foundation, Inc. +Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, +2004, 2005, 2006 Free Software Foundation, Inc. This file is part of Bison, the GNU Compiler Compiler.