X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/d43baf71a71dc0fb20534f401d2b9bdfa6439927..c027cccb351b7b553f92a827787fa91d28934e5c:/TODO diff --git a/TODO b/TODO index 599626f2..74512c4e 100644 --- a/TODO +++ b/TODO @@ -5,43 +5,31 @@ From Franc,ois: should we keep the directory part in the CPP guard? -* URGENT: Documenting C++ output -Write a first documentation for C++ output. +* Yacc.c: CPP Macros +Do some people use YYPURE, YYLSP_NEEDED like we do in the test suite? +They should not: it is not documented. But if they need to, let's +find something clean (not like YYLSP_NEEDED...). -* Documentation -Before releasing, make sure the documentation refers to the current -`output' format. - - -* Error messages -Some are really funky. For instance - - type clash (`%s' `%s') on default action - -is really weird. Revisit them all. +* Installation -* read_pipe.c -This is not portable to DOS for instance. Implement a more portable -scheme. Sources of inspiration include GNU diff, and Free Recode. - - -* value_components_used -Was defined but not used: where was it coming from? It can't be to -check if %union is used, since the user is free to $n on her -union, doesn't she? - +* Documentation +Before releasing, make sure the documentation ("Understanding your +parser") refers to the current `output' format. -* GLR & C++ -Currently, the GLR parser cannot compile with a C++ compiler. +* lalr1.cc +** vector +Move to using vector, drop stack.hh. +** I18n +Catch up with yacc.c. * Report ** GLR How would Paul like to display the conflicted actions? In particular, -what when two reductions are possible on a given lookahead, but one is +what when two reductions are possible on a given lookahead token, but one is part of $default. Should we make the two reductions explicit, or just keep $default? See the following point. @@ -61,34 +49,73 @@ Provide better assistance for understanding the conflicts by providing a sample text exhibiting the (LALR) ambiguity. See the paper from DeRemer and Penello: they already provide the algorithm. +** Statically check for potential ambiguities in GLR grammars. See + for an approach. + * Extensions -** yyerror, yysymprint interface -It should be improved, in particular when using Bison features such as -locations, and YYPARSE_PARAMS. For the time being, it is recommended -to #define yyerror and yyprint to steal internal variables... +** Labeling the symbols +Have a look at the Lemon parser generator: instead of $1, $2 etc. they +can name the values. This is much more pleasant. For instance: + + exp (res): exp (a) '+' exp (b) { $res = $a + $b; }; + +I love this. I have been bitten too often by the removal of the +symbol, and forgetting to shift all the $n to $n-1. If you are +unlucky, it compiles... + +But instead of using $a etc., we can use regular variables. And +instead of using (), I propose to use `:' (again). Paul suggests +supporting `->' in addition to `:' to separate LHS and RHS. In other +words: + + r:exp -> a:exp '+' b:exp { r = a + b; }; + +That requires an significant improvement of the grammar parser. Using +GLR would be nice. It also requires that Bison know the type of the +symbols (which will be useful for %include anyway). So we have some +time before... + +Note that there remains the problem of locations: `@r'? + -** Several %unions -I think this is a pleasant (but useless currently) feature, but in the -future, I want a means to %include other bits of grammars, and _then_ -it will be important for the various bits to define their needs in -%union. +** $-1 +We should find a means to provide an access to values deep in the +stack. For instance, instead of -When implementing multiple-%union support, bare the following in mind: + baz: qux { $$ = $-1 + $0 + $1; } -- when --yacc, this must be flagged as an error. Don't make it fatal - though. +we should be able to have: -- The #line must now appear *inside* the definition of yystype. - Something like + foo($foo) bar($bar) baz($bar): qux($qux) { $baz = $foo + $bar + $qux; } - { - #line 12 "foo.y" - int ival; - #line 23 "foo.y" - char *sval; - } +Or something like this. + +** %if and the like +It should be possible to have %if/%else/%endif. The implementation is +not clear: should it be lexical or syntactic. Vadim Maslow thinks it +must be in the scanner: we must not parse what is in a switched off +part of %if. Akim Demaille thinks it should be in the parser, so as +to avoid falling into another CPP mistake. + +** -D, --define-muscle NAME=VALUE +To define muscles via cli. Or maybe support directly NAME=VALUE? + +** XML Output +There are couple of available extensions of Bison targeting some XML +output. Some day we should consider including them. One issue is +that they seem to be quite orthogonal to the parsing technique, and +seem to depend mostly on the possibility to have some code triggered +for each reduction. As a matter of fact, such hooks could also be +used to generate the yydebug traces. Some generic scheme probably +exists in there. + +XML output for GNU Bison and gcc + http://www.cs.may.ie/~jpower/Research/bisonXML/ + +XML output for GNU Bison + http://yaxx.sourceforge.net/ * Unit rules Maybe we could expand unit rules, i.e., transform @@ -120,23 +147,6 @@ Are there any Texinfo standards for bibliography? * Java, Fortran, etc. -** Java - -There are a couple of proposed outputs: - -- BYACC/J - which is based on Byacc. - - -- Bison Java - which is based on Bison. - - -Sébastien Serrurier (serrur_s@epita.fr) is working on this: he is -expected to contact the authors, design the output, and implement it -into Bison. - - * Coding system independence Paul notes: @@ -150,49 +160,27 @@ Paul notes: PDP-10 ports :-) but they should probably be documented somewhere. - + More importantly, Bison does not currently allow NUL bytes in + tokens, either via escapes (e.g., "x\0y") or via a NUL byte in + the source code. This should get fixed. * --graph -Show reductions. [] +Show reductions. * Broken options ? -** %no-lines [ok] -** %no-parser [] -** %pure-parser [] -** %token-table [] -** Options which could use parse_dquoted_param (). -Maybe transferred in lex.c. -*** %skeleton [ok] -*** %output [] -*** %file-prefix [] -*** %name-prefix [] - -** Skeleton strategy. [] -Must we keep %no-parser? - %token-table? -*** New skeletons. [] +** %token-table +** Skeleton strategy +Must we keep %token-table? * src/print_graph.c -Find the best graph parameters. [] - -* doc/bison.texinfo -** Update -informations about ERROR_VERBOSE. [] -** Add explanations about -skeleton muscles. [] -%skeleton. [] - -* testsuite -** tests/pure-parser.at [] -New tests. - -* input synclines -Some users create their foo.y files, and equip them with #line. Bison -should recognize these, and preserve them. +Find the best graph parameters. * BTYacc -See if we can integrate backtracking in Bison. Contact the BTYacc -maintainers. +See if we can integrate backtracking in Bison. Charles-Henri de +Boysson is working on this, and already has some +results. Vadim Maslow, the maintainer of BTYacc was contacted, and we +stay in touch with him. Adjusting the Bison grammar parser will be +needed to support some extra BTYacc features. This is less urgent. ** Keeping the conflicted actions First, analyze the differences between byacc and btyacc (I'm referring @@ -218,9 +206,6 @@ It is unfortunate that there is a total order for precedence. It makes it impossible to have modular precedence information. We should move to partial orders (sounds like series/parallel orders to me). -This will be possible with a Bison parser for the grammar, as it will -make it much easier to extend the grammar. - ** Correlation b/w precedence and associativity Also, I fail to understand why we have to assign the same associativity to operators with the same precedence. For instance, @@ -300,27 +285,25 @@ at the proper place to bison.simple. Ditto for YYACT_PROLOGUE. I was wondering what you think about adding YYACT_PROLOGUE/EPILOGUE to bison. If you're interested, I'll work on a patch. -* Move to Graphviz -Well, VCG seems really dead. Move to Graphviz instead. Also, equip -the parser with a means to create the (visual) parse tree. +* Better graphics +Equip the parser with a means to create the (visual) parse tree. ----- -Copyright (C) 2001, 2002 Free Software Foundation, Inc. +Copyright (C) 2001, 2002, 2003, 2004, 2006, 2008, 2009, 2010 Free +Software Foundation, Inc. -This file is part of GNU Bison. +This file is part of Bison, the GNU Compiler Compiler. -GNU Bison is free software; you can redistribute it and/or modify +This program 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. +the Free Software Foundation, either version 3 of the License, or +(at your option) any later version. -GNU Bison is distributed in the hope that it will be useful, +This program 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. 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