X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/948be909e9a2f63037190428a6bc54b287ebf79d..2873fdf8b1f91a9cbc8d258367c920eb637a0099:/TODO diff --git a/TODO b/TODO index b21ed19f..7b473094 100644 --- a/TODO +++ b/TODO @@ -1,38 +1,87 @@ -*- outline -*- -* URGENT: Documenting C++ output -Write a first documentation for C++ output. - +* Various +** YYERRCODE +Defined to 256, but not used, not documented. Probably the token +number for the error token, which POSIX wants to be 256, but which +Bison might renumber if the user used number 256. Keep fix and doc? +Throw away? + +** YYFAIL +It is seems to be *really* obsolete now, shall we remove it? + +** YYBACKUP +There is no test about it, no examples in the doc, and I'm not sure +what it should look like. For instance what follows crashes. + + %error-verbose + %debug + %pure-parser + %code { + # include + # include + # include + + static void yyerror (const char *msg); + static int yylex (YYSTYPE *yylval); + } + %% + exp: + 'a' { printf ("a: %d\n", $1); } + | 'b' { YYBACKUP('a', 123); } + ; + %% + static int + yylex (YYSTYPE *yylval) + { + static char const input[] = "b"; + static size_t toknum; + assert (toknum < sizeof input); + *yylval = (toknum + 1) * 10; + return input[toknum++]; + } + + static void + yyerror (const char *msg) + { + fprintf (stderr, "%s\n", msg); + } + + int + main (void) + { + yydebug = !!getenv("YYDEBUG"); + return yyparse (); + } + + +* Header guards + +From Franc,ois: should we keep the directory part in the CPP guard? + + +* 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...). + + +* Installation * 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. - - -* 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? +Before releasing, make sure the documentation ("Understanding your +parser") refers to the current `output' format. +* lalr1.cc +** 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. @@ -52,34 +101,70 @@ 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'? + + +** $-1 +We should find a means to provide an access to values deep in the +stack. For instance, instead of -** 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. + baz: qux { $$ = $-1 + $0 + $1; } -When implementing multiple-%union support, bare the following in mind: +we should be able to have: -- when --yacc, this must be flagged as an error. Don't make it fatal - though. + foo($foo) bar($bar) baz($bar): qux($qux) { $baz = $foo + $bar + $qux; } -- The #line must now appear *inside* the definition of yystype. - Something like +Or something like this. - { - #line 12 "foo.y" - int ival; - #line 23 "foo.y" - char *sval; - } +** %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. + +** 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 @@ -110,12 +195,6 @@ Are there any Texinfo standards for bibliography? * Java, Fortran, etc. - Add support for languages other than C and C++. Here is a proposed - patch for Java: - - - - * Coding system independence Paul notes: @@ -130,49 +209,26 @@ 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. [] - -* 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. +** %token-table +** Skeleton strategy +Must we keep %token-table? * 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 has been working on this, but never gave +the results. + +Vadim Maslow, the maintainer of BTYacc was once contacted. 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 @@ -187,9 +243,6 @@ very feasible to use the very same conflict tables. ** Adjust the skeletons Import the skeletons for C and C++. -** Improve the skeletons -Have them support yysymprint, yydestruct and so forth. - * Precedence @@ -198,18 +251,6 @@ 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, -why can't I decide that the precedence of * and / is the same, but the -latter is nonassoc? - -If there is really no profound motivation, we should find a new syntax -to allow specifying this. - ** RR conflicts See if we can use precedence between rules to solve RR conflicts. See what POSIX says. @@ -238,20 +279,6 @@ $$ = $1. I therefore think that one should implement a Bison option where every typed default rule is explicitly written out (same typed ruled can of course be grouped together). -Note: Robert Anisko handles this. He knows how to do it. - - -* Warnings -It would be nice to have warning support. See how Autoconf handles -them, it is fairly well described there. It would be very nice to -implement this in such a way that other programs could use -lib/warnings.[ch]. - -Don't work on this without first announcing you do, as I already have -thought about it, and know many of the components that can be used to -implement it. - - * Pre and post actions. From: Florian Krohm Subject: YYACT_EPILOGUE @@ -280,27 +307,25 @@ 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 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. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License -along with Bison; see the file COPYING. If not, write to -the Free Software Foundation, Inc., 59 Temple Place - Suite 330, -Boston, MA 02111-1307, USA. +along with this program. If not, see .