X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/2ce1014469742b5c6618daf8506b69e38787c7d5..721be13c5b708d14e96f94f825768a77e13131bb:/NEWS?ds=inline diff --git a/NEWS b/NEWS index fabc23b0..176ce6f2 100644 --- a/NEWS +++ b/NEWS @@ -1,9 +1,586 @@ Bison News ---------- -Changes in version 1.28b: +Changes in version 2.1a: -* the input and the output files has automatically a similar extension. +* New warning: unused values + Typed right-hand side symbols whose value are not used are reported. + For instance: + + exp: exp "?" exp ":" exp { $$ = $1 ? $1 : $3; } + | exp "+" exp + ; + + will trigger a warning about $5 of the first rule, and $3 in the + second ($1 is copied to $$ by the default rule). This example + most likely contains two errors, and should be rewritten as: + + exp: exp "?" exp ":" exp { $$ = $1 ? $3 : $5; } + | exp "+" exp { $$ = $1 + $3; } + ; + + However, if the original actions were really intended, 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) $3; } + ; + + The warning is intended to help catching lost values and memory leaks. + If a value is ignored, its associated memory typically is not reclaimed. + +* %destructor vs. YYABORT, YYACCEPT, and YYERROR. + Destructors are now called when user code invokes YYABORT, YYACCEPT, + and YYERROR, for all objects on the stack, other than objects + corresponding to the right-hand side of the current rule. + +* %expect, %expect-rr + Incorrect numbers of expected conflicts are now actual errors, + instead of warnings. + +* GLR, YACC parsers. + The %parse-params are available in the %destructor's (and the + experimental %printer's) as per the documentation. + +* Bison now warns if it finds a stray `$' or `@' in an action. + +* %require "VERSION" + To specify 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. + +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. + +* 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 + + - 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. + + - `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. + + - The documentation now emphasizes that yylex and yyerror must be + declared before use. C99 requires this. + + - Bison now parses C99 lexical constructs like UCNs and + backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires. + + - File names are properly escaped in C output. E.g., foo\bar.y is + output as "foo\\bar.y". + + - 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. + + - Type clashes now generate warnings, not errors. + + - 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. + +* Other compatibility issues + + - %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. + + - `;' is output before the terminating `}' of an action, for + compatibility with Bison 1.35. + + - Bison now uses a Yacc-style format for conflict reports, e.g., + `conflicts: 2 shift/reduce, 1 reduce/reduce'. + + - `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. + +* Indonesian translation thanks to Tedi Heriyanto. + +* GLR parsers + Fix spurious parse errors. + +* Pure parsers + Some people redefine yyerror to steal yyparse' private variables. + Reenable this trick until an official feature replaces it. + +* Type Clashes + In agreement with POSIX and with other Yaccs, leaving a default + action is valid when $$ is untyped, and $1 typed: + + untyped: ... typed; + + but the converse remains an error: + + typed: ... untyped; + +* Values of mid-rule actions + The following code: + + foo: { ... } { $$ = $1; } ... + + 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 + The declaration + %glr-parser + causes Bison to produce a Generalized LR (GLR) parser, capable of handling + almost any context-free grammar, ambiguous or not. The new declarations + %dprec and %merge on grammar rules allow parse-time resolution of + ambiguities. Contributed by Paul Hilfinger. + + Unfortunately Bison 1.50 does not work properly on 64-bit hosts + like the Alpha, so please stick to 32-bit hosts for now. + +* Output Directory + When not in Yacc compatibility mode, when the output file was not + specified, running `bison foo/bar.y' created `foo/bar.c'. It + now creates `bar.c'. + +* Undefined token + The undefined token was systematically mapped to 2 which prevented + the use of 2 by the user. This is no longer the case. + +* Unknown token numbers + If yylex returned an out of range value, yyparse could die. This is + no longer the case. + +* Error token + According to POSIX, the error token must be 256. + Bison extends this requirement by making it a preference: *if* the + user specified that one of her tokens is numbered 256, then error + will be mapped onto another number. + +* Verbose error messages + They no longer report `..., expecting error or...' for states where + error recovery is possible. + +* End token + Defaults to `$end' instead of `$'. + +* Error recovery now conforms to documentation and to POSIX + When a Bison-generated parser encounters a syntax error, it now pops + the stack until it finds a state that allows shifting the error + token. Formerly, it popped the stack until it found a state that + 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. + +* Larger grammars + Larger grammars are now supported (larger token numbers, larger grammar + size (= sum of the LHS and RHS lengths), larger LALR tables). + Formerly, many of these numbers ran afoul of 16-bit limits; + now these limits are 32 bits on most hosts. + +* Explicit initial rule + Bison used to play hacks with the initial rule, which the user does + not write. It is now explicit, and visible in the reports and + graphs as rule 0. + +* Useless rules + Before, Bison reported the useless rules, but, although not used, + included them in the parsers. They are now actually removed. + +* Useless rules, useless nonterminals + They are now reported, as a warning, with their locations. + +* Rules never reduced + Rules that can never be reduced because of conflicts are now + reported. + +* Incorrect `Token not used' + On a grammar such as + + %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. + +* Revert the C++ namespace changes introduced in 1.31 + as they caused too many portability hassles. + +* Default locations + By an accident of design, the default computation of @$ was + performed after another default computation was performed: @$ = @1. + The latter is now removed: YYLLOC_DEFAULT is fully responsible of + the computation of @$. + +* Token end-of-file + The token end of file may be specified by the user, in which case, + 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 + or + %token MYEOF 0 "end of file" + +* Semantic parser + This old option, which has been broken for ages, is removed. + +* New translations + Brazilian Portuguese, thanks to Alexandre Folle de Menezes. + Croatian, thanks to Denis Lackovic. + +* Incorrect token definitions + When given `%token 'a' "A"', Bison used to output `#define 'a' 65'. + +* Token definitions as enums + Tokens are output both as the traditional #define's, and, provided + the compiler supports ANSI C or is a C++ compiler, as enums. + This lets debuggers display names instead of integers. + +* Reports + In addition to --verbose, bison supports --report=THINGS, which + 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 + - solved + describe shift/reduce conflicts solving. + Bison used to systematically output this information on top of + the report. Solved conflicts are now attached to their states. + +* Type clashes + 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'; + + This is fixed. + +* GNU M4 is now required when using Bison. + +Changes in version 1.35, 2002-03-25: + +* C Skeleton + Some projects use Bison's C parser with C++ compilers, and define + YYSTYPE as a class. The recent adjustment of C parsers for data + alignment and 64 bit architectures made this impossible. + + Because for the time being no real solution for C++ parser + generation exists, kludges were implemented in the parser to + maintain this use. In the future, when Bison has C++ parsers, this + kludge will be disabled. + + This kludge also addresses some C++ problems when the stack was + extended. + +Changes in version 1.34, 2002-03-12: + +* File name clashes are detected + $ bison foo.y -d -o foo.x + fatal error: header and parser would both be named `foo.x' + +* A missing `;' at the end of a rule triggers a warning + In accordance with POSIX, and in agreement with other + Yacc implementations, Bison will mandate this semicolon in the near + future. This eases the implementation of a Bison parser of Bison + grammars by making this grammar LALR(1) instead of LR(2). To + facilitate the transition, this release introduces a warning. + +* Revert the C++ namespace changes introduced in 1.31, as they caused too + many portability hassles. + +* DJGPP support added. + +* Fix test suite portability problems. + +Changes in version 1.33, 2002-02-07: + +* Fix C++ issues + Groff could not be compiled for the definition of size_t was lacking + under some conditions. + +* Catch invalid @n + As is done with $n. + +Changes in version 1.32, 2002-01-23: + +* Fix Yacc output file names + +* Portability fixes + +* Italian, Dutch translations + +Changes in version 1.31, 2002-01-14: + +* Many Bug Fixes + +* GNU Gettext and %expect + GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that + Bison dies on incorrect %expectations, we fear there will be + too many bug reports for Gettext, so _for the time being_, %expect + does not trigger an error when the input file is named `plural.y'. + +* Use of alloca in parsers + If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use + malloc exclusively. Since 1.29, but was not NEWS'ed. + + 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. + +* User Actions + Bison has always permitted actions such as { $$ = $1 }: it adds the + ending semicolon. Now if in Yacc compatibility mode, the semicolon + is no longer output: one has to write { $$ = $1; }. + +* Better C++ compliance + The output parsers try to respect C++ namespaces. + [This turned out to be a failed experiment, and it was reverted later.] + +* Reduced Grammars + Fixed bugs when reporting useless nonterminals. + +* 64 bit hosts + The parsers work properly on 64 bit hosts. + +* Error messages + Some calls to strerror resulted in scrambled or missing error messages. + +* %expect + When the number of shift/reduce conflicts is correct, don't issue + any warning. + +* The verbose report includes the rule line numbers. + +* Rule line numbers are fixed in traces. + +* Swedish translation + +* Parse errors + Verbose parse error messages from the parsers are better looking. + Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'('' + Now: parse error: unexpected '/', expecting "number" or '-' or '(' + +* Fixed parser memory leaks. + When the generated parser was using malloc to extend its stacks, the + previous allocations were not freed. + +* Fixed verbose output file. + Some newlines were missing. + Some conflicts in state descriptions were missing. + +* Fixed conflict report. + Option -v was needed to get the result. + +* %expect + Was not used. + Mismatches are errors, not warnings. + +* Fixed incorrect processing of some invalid input. + +* Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H. + +* Fixed some typos in the documentation. + +* %token MY_EOF 0 is supported. + Before, MY_EOF was silently renumbered as 257. + +* doc/refcard.tex is updated. + +* %output, %file-prefix, %name-prefix. + New. + +* --output + New, aliasing `--output-file'. + +Changes in version 1.30, 2001-10-26: + +* `--defines' and `--graph' have now an optional argument which is the + output file name. `-d' and `-g' do not change; they do not take any + argument. + +* `%source_extension' and `%header_extension' are removed, failed + experiment. + +* Portability fixes. + +Changes in version 1.29, 2001-09-07: + +* The output file does not define const, as this caused problems when used + with common autoconfiguration schemes. If you still use ancient compilers + that lack const, compile with the equivalent of the C compiler option + `-Dconst='. autoconf's AC_C_CONST macro provides one way to do this. + +* Added `-g' and `--graph'. + +* The Bison manual is now distributed under the terms of the GNU FDL. + +* The input and the output files has automatically a similar extension. * Russian translation added. @@ -21,10 +598,13 @@ Changes in version 1.28b: of the #line lines with path names including backslashes. * New directives. - `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose', and - `%debug'. + `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose', + `%debug', `%source_extension' and `%header_extension'. + +* @$ + Automatic location tracking. -Changes in version 1.28: +Changes in version 1.28, 1999-07-06: * Should compile better now with K&R compilers. @@ -56,7 +636,7 @@ Changes in version 1.26: * Generated parsers should now work even on operating systems which do not provide alloca(). -Changes in version 1.25: +Changes in version 1.25, 1995-10-16: * Errors in the input grammar are not fatal; Bison keeps reading the grammar file, and reports all the errors found in it. @@ -97,3 +677,29 @@ Changes in version 1.22: Changes in version 1.20: Output file does not redefine const for C++. + +Local Variables: +mode: outline +End: + +----- + +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. + +Bison is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +Bison is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +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., 51 Franklin Street, Fifth Floor, +Boston, MA 02110-1301, USA.