X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/75eb3bc4e7e48c5c247ede3a7ae0f0750bf0e3e8..2c3b392a9ad550ca87f6e5172072cd0b70b15f1d:/NEWS diff --git a/NEWS b/NEWS index d8b63b24..29310169 100644 --- a/NEWS +++ b/NEWS @@ -1,99 +1,232 @@ Bison News ---------- -Changes in version 1.75e: +Changes in version 2.1a: -* If the user does not define YYSTYPE as a macro, Bison now declares it - using typedef instead of defining it as a macro. POSIX requires this. - For consistency, YYLTYPE is also declared instead of defined. +* %destructor vs. YYACCEPT, YYERROR, and YYABORT. + When the parsing/action is cut by the user using one of these + special actions, the stack is freed except the right-hand side + symbols of the current rule. -* %union directives can now have a tag before the `{', e.g., the - directive `%union foo {...}' now generates the C code - `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility. - The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc. - For consistency, YYLTYPE's struct tag is now `YYLTYPE' instead of `yyltype'. +* GLR, C++ LALR(1) parsers. + These parser skeletons are now distributed with the same special + license exception that the C LALR(1) parser skeleton has had since + Bison 1.24. Hence the FSF imposes no copyright restriction on the + output of Bison when it is generating such parsers. -* `yystype' and `yyltype' are now obsolescent macros instead of being - typedefs or tags; they are no longer documented and will be - withdrawn in a future release. +* %expect, %expect-rr + Incorrect numbers of expected conflicts are now actual errors, + instead of warnings. -* References to the experimental %lex-param and %parse-param directives - have been temporarily removed from the manual, since we don't want - users to rely upon these features quite yet. +* GLR, YACC parsers. + The %parse-params are available in the %destructor's (and the + experimental %printer's) as per the documentation. -Changes in version 1.75d, 2002-12-13: +* Bison now warns if it finds a stray `$' or `@' in an action. -* Semicolons are once again optional at the end of grammar rules. - This reverts to the behavior of Bison 1.33 and earlier, and improves - compatibility with Yacc. +* %require "VERSION" + To specify that the grammar file depends on features implemented in + Bison version VERSION or higher. -* Type clashes now generate warnings, not errors. +* 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. -* Yacc command and library now available - The Bison distribution now installs a yacc command, as POSIX requires. - Also, Bison now installs a small library liby.a containing - implementations of Yacc-compatible yyerror and main functions. - This library is normally not useful, but POSIX requires it. + 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. -* %lex-param, %parse-param - These now take just one operand, not two. + If you wish to update, then make sure older version of Bison will + fail using `%require "2.1a"'. -* The documentation now emphasizes that yylex and yyerror must be - declared before use. C99 requires this. +* 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 + Internationalization section of the Bison manual. Software + distributors should also see the new PACKAGING file. Thanks to + Bruno Haible for this new feature. + +* Wording in the Bison-generated parsers has been changed slightly to + simplify translation. In particular, the message "memory exhausted" + has replaced "parser stack overflow", as the old message was not + always accurate for modern Bison-generated parsers. + +* Destructors are now called when the parser aborts, for all symbols left + behind on the stack. Also, the start symbol is now destroyed after a + successful parse. In both cases, the behavior was formerly inconsistent. + +* When generating verbose diagnostics, Bison-generated parsers no longer + quote the literal strings associated with tokens. For example, for + 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 + + - Bison-generated parsers no longer default to using the alloca function + (when available) to extend the parser stack, due to widespread + problems in unchecked stack-overflow detection. You can "#define + YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read + the manual to determine safe values for YYMAXDEPTH in that case. + + - Error token location. + During error recovery, the location of the syntax error is updated + to cover the whole sequence covered by the error token: it includes + the shifted symbols thrown away during the first part of the error + recovery, and the lookahead rejected during the second part. + + - Semicolon changes: + . Stray semicolons are no longer allowed at the start of a grammar. + . Semicolons are now required after in-grammar declarations. + + - Unescaped newlines are no longer allowed in character constants or + string literals. They were never portable, and GCC 3.4.0 has + dropped support for them. Better diagnostics are now generated if + forget a closing quote. + + - NUL bytes are no longer allowed in Bison string literals, unfortunately. + +* New features + + - GLR grammars now support locations. + + - New directive: %initial-action. + This directive allows the user to run arbitrary code (including + initializing @$) from yyparse before parsing starts. + + - A new directive "%expect-rr N" specifies the expected number of + reduce/reduce conflicts in GLR parsers. + + - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'. + 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. + + - Experimental %destructor support has been added to lalr1.cc. + + - New configure option --disable-yacc, to disable installation of the + yacc command and -ly library introduced in 1.875 for POSIX conformance. + +* Bug fixes + + - For now, %expect-count violations are now just warnings, not errors. + This is for compatibility with Bison 1.75 and earlier (when there are + reduce/reduce conflicts) and with Bison 1.30 and earlier (when there + are too many or too few shift/reduce conflicts). However, in future + versions of Bison we plan to improve the %expect machinery so that + these violations will become errors again. + + - Within Bison itself, numbers (e.g., goto numbers) are no longer + arbitrarily limited to 16-bit counts. + + - Semicolons are now allowed before "|" in grammar rules, as POSIX requires. + +Changes in version 1.875, 2003-01-01: * The documentation license has been upgraded to version 1.2 of the GNU Free Documentation License. -Changes in version 1.75c, 2002-11-25: +* syntax error processing + + - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error + locations too. This fixes bugs in error-location computation. + + - %destructor + It is now possible to reclaim the memory associated to symbols + discarded during error recovery. This feature is still experimental. + + - %error-verbose + This new directive is preferred over YYERROR_VERBOSE. + + - #defining yyerror to steal internal variables is discouraged. + It is not guaranteed to work forever. + +* POSIX conformance -* "parse error" -> "syntax error" - Bison now uniformly uses the term "syntax error"; formerly, the code - and manual sometimes used the term "parse error" instead. POSIX - requires "syntax error" in diagnostics, and it was thought better to - be consistent. + - Semicolons are once again optional at the end of grammar rules. + This reverts to the behavior of Bison 1.33 and earlier, and improves + compatibility with Yacc. -* "parsing stack overflow..." -> "parser stack overflow" - GLR parsers now report "parser stack overflow" as per the Bison manual. + - `parse error' -> `syntax error' + Bison now uniformly uses the term `syntax error'; formerly, the code + and manual sometimes used the term `parse error' instead. POSIX + requires `syntax error' in diagnostics, and it was thought better to + be consistent. -* GLR and inline - Users of Bison have to decide how they handle the portability of the - C keyword `inline'. + - The documentation now emphasizes that yylex and yyerror must be + declared before use. C99 requires this. -Changes in version 1.75b, 2002-11-13: + - Bison now parses C99 lexical constructs like UCNs and + backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires. -* %destructor - It is now possible to reclaim the memory associated to symbols - discarded during error recovery. This feature is still experimental. + - File names are properly escaped in C output. E.g., foo\bar.y is + output as "foo\\bar.y". -* Bison now parses C99 lexical constructs like UCNs and - backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires. + - Yacc command and library now available + The Bison distribution now installs a `yacc' command, as POSIX requires. + Also, Bison now installs a small library liby.a containing + implementations of Yacc-compatible yyerror and main functions. + This library is normally not useful, but POSIX requires it. -* --no-line works properly. + - Type clashes now generate warnings, not errors. -* %error-verbose - This new directive is preferred over YYERROR_VERBOSE. + - If the user does not define YYSTYPE as a macro, Bison now declares it + using typedef instead of defining it as a macro. + For consistency, YYLTYPE is also declared instead of defined. -* %lex-param, %parse-param - These new directives are preferred over PARSE_PARAM and LEX_PARAM. - In addition, they provide a means for yyerror to remain pure, and - to access to the current location. +* Other compatibility issues - #defining yyerror to steal internal variables is strongly - discouraged. It is not guaranteed to work for ever. + - %union directives can now have a tag before the `{', e.g., the + directive `%union foo {...}' now generates the C code + `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility. + The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc. + For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'. + This is for compatibility with both Yacc and Bison 1.35. -* #line - Bison now recognizes #line in its input, and forwards them. + - `;' is output before the terminating `}' of an action, for + compatibility with Bison 1.35. -* #line - File names are properly escaped. E.g. foo\bar.y give #line 123 "foo\\bar.y". + - Bison now uses a Yacc-style format for conflict reports, e.g., + `conflicts: 2 shift/reduce, 1 reduce/reduce'. -Changes in version 1.75a, 2002-10-24: + - `yystype' and `yyltype' are now obsolescent macros instead of being + typedefs or tags; they are no longer documented and are planned to be + withdrawn in a future release. + +* GLR parser notes + + - GLR and inline + Users of Bison have to decide how they handle the portability of the + C keyword `inline'. + + - `parsing stack overflow...' -> `parser stack overflow' + GLR parsers now report `parser stack overflow' as per the Bison manual. + +* 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. + +* #line in output files + - --no-line works properly. * Bison can no longer be built by a K&R C compiler; it requires C89 or later to be built. This change originally took place a few versions ago, but nobody noticed until we recently asked someone to try building Bison with a K&R C compiler. - + Changes in version 1.75, 2002-10-14: * Bison should now work on 64-bit hosts. @@ -124,7 +257,7 @@ Changes in version 1.75, 2002-10-14: was incorrectly rejected: $1 is defined in the second mid-rule action, and is equal to the $$ of the first mid-rule action. - + Changes in version 1.50, 2002-10-04: * GLR parsing @@ -171,7 +304,8 @@ Changes in version 1.50, 2002-10-04: allowed some non-error action other than a default reduction on the error token. The new behavior has long been the documented behavior, and has long been required by POSIX. For more details, please see - . + Paul Eggert, "Reductions during Bison error handling" (2002-05-20) + . * Traces Popped tokens and nonterminals are now reported. @@ -246,8 +380,8 @@ Changes in version 1.50, 2002-10-04: produces additional information: - itemset complete the core item sets with their closure - - lookahead - explicitly associate lookaheads to items + - lookahead [changed to `look-ahead' in 1.875e and later] + explicitly associate look-ahead tokens to items - solved describe shift/reduce conflicts solving. Bison used to systematically output this information on top of @@ -334,6 +468,8 @@ Changes in version 1.31, 2002-01-14: alloca is used only when compiled with GCC, to avoid portability problems as on AIX. +* yyparse now returns 2 if memory is exhausted; formerly it dumped core. + * When the generated parser lacks debugging code, YYDEBUG is now 0 (as POSIX requires) instead of being undefined. @@ -528,8 +664,8 @@ End: ----- -Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002 Free -Software Foundation, Inc. +Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 +Free Software Foundation, Inc. This file is part of Bison, the GNU Compiler Compiler. @@ -545,5 +681,5 @@ GNU General Public License for more details. You should have received a copy of the GNU General Public License along with autoconf; see the file COPYING. If not, write to -the Free Software Foundation, Inc., 59 Temple Place - Suite 330, -Boston, MA 02111-1307, USA. +the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, +Boston, MA 02110-1301, USA.