Update TODO.

[bison.git] / TODO

diff --git a/TODO b/TODO
index 4762559ea2e2674621f7b14ca437ebd4e645eaea..7b473094cf7d7450ea66b48e618f7ead857d6465 100644 (file)
--- a/TODO
+++ b/TODO
@@ -1,5 +1,60 @@
 -*- outline -*-
 
 -*- outline -*-
 

+* 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 <stdio.h>
+  # include <stdlib.h>
+  # include <assert.h>
+
+    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?
 * Header guards
 
 From Franc,ois: should we keep the directory part in the CPP guard?


@@ -12,24 +67,21 @@ They should not: it is not documented.  But if they need to, let's
 find something clean (not like YYLSP_NEEDED...).
 
 
 find something clean (not like YYLSP_NEEDED...).
 
 

-* URGENT: Documenting C++ output
-Write a first documentation for C++ output.
-
+* Installation

 
 * Documentation
 Before releasing, make sure the documentation ("Understanding your
 parser") refers to the current `output' format.
 
 
 * 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
+** I18n
+Catch up with yacc.c.

 
 * Report
 
 **  GLR
 How would Paul like to display the conflicted actions?  In particular,
 
 * Report
 
 **  GLR
 How would Paul like to display the conflicted actions?  In particular,

-what when two reductions are possible on a given look-ahead token, 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.
 
 part of $default.  Should we make the two reductions explicit, or just
 keep $default?  See the following point.
 


@@ -49,17 +101,13 @@ 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.
 
 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
+<http://www.i3s.unice.fr/~schmitz/papers.html#expamb> for an approach.

 
 

-* Extensions

 
 

-** %destructor
-I think we should document it as experimental, and allow its use in
-the next releases.  But we also need to port it to GLR.  What about
-lalr1.cc?  Well, read what Hans reported, maybe we don't want
-%detructor.  On the other hand, there is no reason not to provide it:
-users can avoid its use.
+* Extensions

 
 

-** $foo
+** 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:
 
 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:
 


@@ -69,6 +117,21 @@ 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...
 
 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
 ** $-1
 We should find a means to provide an access to values deep in the
 stack.  For instance, instead of


@@ -81,32 +144,6 @@ we should be able to have:
 
 Or something like this.
 
 
 Or something like this.
 

-** yysymprint interface
-It should be improved, in particular when using Bison features such as
-locations, and YYPARSE_PARAMS.  For the time being, it is almost
-recommended to yyprint to steal internal variables...
-
-** 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.
-
-When implementing multiple-%union support, bare the following in mind:
-
-- when --yacc, this must be flagged as an error.  Don't make it fatal
-  though.
-
-- The #line must now appear *inside* the definition of yystype.
-  Something like
-
-       {
-       #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
 ** %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


@@ -114,9 +151,6 @@ 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.
 
 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
 ** XML Output
 There are couple of available extensions of Bison targeting some XML
 output.  Some day we should consider including them.  One issue is


@@ -162,23 +196,6 @@ Are there any Texinfo standards for bibliography?
 * Java, Fortran, etc.
 
 
 * Java, Fortran, etc.
 
 

-** Java
-
-There are a couple of proposed outputs:
-
-- BYACC/J
-  which is based on Byacc.
-  <http://troi.lincom-asg.com/~rjamison/byacc/>
-
-- Bison Java
-  which is based on Bison.
-  <http://www.goice.co.jp/member/mo/hack-progs/bison-java.html>
-
-Sebastien 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:
 
 * Coding system independence
 Paul notes:
 


@@ -192,38 +209,26 @@ Paul notes:
        PDP-10 ports :-) but they should probably be documented
        somewhere.
 
        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
 
 * --graph

-Show reductions.       []
+Show reductions.

 
 * Broken options ?
 
 * Broken options ?

-** %no-parser          []
-** %token-table                []
-** Skeleton strategy.  []
-Must we keep %no-parser?
-            %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.
+** %token-table
+** Skeleton strategy
+Must we keep %token-table?

 
 * BTYacc
 See if we can integrate backtracking in Bison.  Charles-Henri de
 
 * BTYacc
 See if we can integrate backtracking in Bison.  Charles-Henri de

-Boysson <de-boy_c@epita.fr> 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.
+Boysson <de-boy_c@epita.fr> 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
 
 ** Keeping the conflicted actions
 First, analyze the differences between byacc and btyacc (I'm referring


@@ -238,9 +243,6 @@ very feasible to use the very same conflict tables.
 ** Adjust the skeletons
 Import the skeletons for C and C++.
 
 ** Adjust the skeletons
 Import the skeletons for C and C++.
 

-** Improve the skeletons
-Have them support yysymprint, yydestruct and so forth.
-

 
 * Precedence
 
 
 * Precedence
 


@@ -249,18 +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).
 
 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.
 ** RR conflicts
 See if we can use precedence between rules to solve RR conflicts.  See
 what POSIX says.


@@ -289,20 +279,6 @@ $<type_name>$ = $<type_name>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).
 
 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 <florian@edamail.fishkill.ibm.com>
 Subject: YYACT_EPILOGUE
 * Pre and post actions.
 From: Florian Krohm <florian@edamail.fishkill.ibm.com>
 Subject: YYACT_EPILOGUE


@@ -331,27 +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.
 
 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, 2003, 2004 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
 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.
 
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+along with this program.  If not, see <http://www.gnu.org/licenses/>.