Define make_symbol in the header.

[bison.git] / TODO

diff --git a/TODO b/TODO
index 56038fc633fe45fe039748ce7fffda704db774a4..9dbd6b423e4cd88e45eab24c78175e22458c18f6 100644 (file)
--- a/TODO
+++ b/TODO
@@ -1,62 +1,120 @@
 -*- outline -*-
 
 -*- 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 <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 ();
+  }
+
+** yychar == yyempty_
+The code in yyerrlab reads:
+
+      if (yychar <= YYEOF)
+       {
+         /* Return failure if at end of input.  */
+         if (yychar == YYEOF)
+           YYABORT;
+       }

 
 

-* Documentation
-Before releasing, make sure the documentation refers to the current
-`output' format.
+There are only two yychar that can be <= YYEOF: YYEMPTY and YYEOF.
+But I can't produce the situation where yychar is YYEMPTY here, is it
+really possible?  The test suite does not exercise this case.

 
 

+This shows that it would be interesting to manage to install skeleton
+coverage analysis to the test suite.

 
 

-* Error messages
-Some are really funky.  For instance
+** Table definitions
+It should be very easy to factor the definition of the various tables,
+including the separation bw declaration and definition.  See for
+instance b4_table_define in lalr1.cc.  This way, we could even factor
+C vs. C++ definitions.

 
 

-       type clash (`%s' `%s') on default action
+* From lalr1.cc to yacc.c
+** Single stack
+Merging the three stacks in lalr1.cc simplified the code, prompted for
+other improvements and also made it faster (probably because memory
+management is performed once instead of three times).  I suggest that
+we do the same in yacc.c.

 
 

-is really weird.  Revisit them all.
+** yysyntax_error
+In lalr1.cc we invoke it with the translated lookahead (yytoken), and
+yacc.c uses yychar.  I don't see why.

 
 

-* Stupid error messages
-An example shows it easily:
+** yysyntax_error
+The use of switch to select yyfmt in lalr1.cc seems simpler than
+what's done in yacc.c.

 
 

-src/bison/tests % ./testsuite -k calc,location,error-verbose -l
-GNU Bison 1.49a test suite test groups:
+* Header guards

 
 

- NUM: FILENAME:LINE      TEST-GROUP-NAME
-      KEYWORDS
+From Franc,ois: should we keep the directory part in the CPP guard?

 
 

-  51: calc.at:440        Calculator --locations --yyerror-verbose
-  52: calc.at:442        Calculator --defines --locations --name-prefix=calc --verbose --yacc --yyerror-verbose
-  54: calc.at:445        Calculator --debug --defines --locations --name-prefix=calc --verbose --yacc --yyerror-verbose
-src/bison/tests % ./testsuite 51 -d
-## --------------------------- ##
-## GNU Bison 1.49a test suite. ##
-## --------------------------- ##
- 51: calc.at:440       ok
-## ---------------------------- ##
-## All 1 tests were successful. ##
-## ---------------------------- ##
-src/bison/tests % cd ./testsuite.dir/51
-tests/testsuite.dir/51 % echo "()" | ./calc
-1.2-1.3: parse error, unexpected ')', expecting error or "number" or '-' or '('

 
 

+* Yacc.c: CPP Macros

 
 

-* 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.
+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...).

 
 
 
 

-* 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 $<foo>n on her
-union, doesn't she?
+* Installation

 
 

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

 
 * 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 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.
 
 part of $default.  Should we make the two reductions explicit, or just
 keep $default?  See the following point.
 


@@ -76,34 +134,70 @@ 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.
 
 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.

 
 

-* Extentions

 
 

-** 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...
+* Extensions

 
 

-** 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.
+** 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:

 
 

-When implementing multiple-%union support, bare the following in mind:
+       exp (res): exp (a) '+' exp (b) { $res = $a + $b; };

 
 

-- when --yacc, this must be flagged as an error.  Don't make it fatal
-  though.
+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...

 
 

-- The #line must now appear *inside* the definition of yystype.
-  Something like
+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:

 
 

-       {
-       #line 12 "foo.y"
-         int ival;
-       #line 23 "foo.y"
-         char *sval;
-       }
+       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
+
+       baz: qux { $$ = $<foo>-1 + $<bar>0 + $1; }
+
+we should be able to have:
+
+  foo($foo) bar($bar) baz($bar): qux($qux) { $baz = $foo + $bar + $qux; }
+
+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.
+
+** 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
 
 * Unit rules
 Maybe we could expand unit rules, i.e., transform


@@ -132,6 +226,8 @@ Are there any Texinfo standards for bibliography?
 
 
 
 
 
 

+* Java, Fortran, etc.
+

 
 * Coding system independence
 Paul notes:
 
 * Coding system independence
 Paul notes:


@@ -146,56 +242,33 @@ 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-lines           [ok]
-** %no-parser          []
-** %pure-parser                []
-** %token-table                []
-** Options which could use parse_dquoted_param ().
-Maybe transfered 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 explainations 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
 
 * 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 <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
 to the executables).  Find where the conflicts are preserved.
 
 ** Compare with the GLR tables
 
 ** Keeping the conflicted actions
 First, analyze the differences between byacc and btyacc (I'm referring
 to the executables).  Find where the conflicts are preserved.
 
 ** Compare with the GLR tables

-See how isomorphic the way BTYacc and the way the GLR adjustements in
+See how isomorphic the way BTYacc and the way the GLR adjustments in

 Bison are compatible.  *As much as possible* one should try to use the
 same implementation in the Bison executables.  I insist: it should be
 very feasible to use the very same conflict tables.
 Bison are compatible.  *As much as possible* one should try to use the
 same implementation in the Bison executables.  I insist: it should be
 very feasible to use the very same conflict tables.


@@ -203,9 +276,6 @@ 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
 


@@ -214,18 +284,6 @@ 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.


@@ -254,20 +312,6 @@ $<type_name>$ = $<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


@@ -296,27 +340,25 @@ 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 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.
 
 You should have received a copy of the GNU General Public License
 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 <http://www.gnu.org/licenses/>.