Bison test version 2.1a is now available. It contains mostly bug fixes for Bison 2.1, but there are few new features, notably in the area of better support for destructors. Our intention is to generate a new official release soon, based on feedback from this test version.
Here is the URL: ftp://alpha.gnu.org/gnu/bison/bison-2.1a.tar.gz Here is the MD5 checksum: 021d6072cf0dea923b54d19ab3c2ced0 bison-2.1a.tar.gz To try this test version, please make sure you have GNU m4 1.4.4 <ftp://ftp.gnu.org/gnu/m4/m4-1.4.4.tar.gz> installed, and then execute the following shell commands or their equivalents: wget ftp://alpha.gnu.org/gnu/bison/bison-2.1a.tar.gz gunzip <bison-2.1a.tar.gz | tar xf - cd bison-2.1a ./configure make make check We particularly appreciate tests on unusual hosts. Please report bugs to <bug-bison@gnu.org>. Bison is a parser generator that is compatible with Yacc. Please see <http://www.gnu.org/software/bison/> for more info about Bison. Here is a list of user-visible changes in version 2.1a, compared to 2.1: * Bison now allows multiple %union declarations, and concatenates their contents together. * New warning: unused values Typed right-hand side symbols whose values are not used are reported, if the associated types 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 "2.1a"'. * DJGPP support added. _______________________________________________ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison