-*- outline -*-
+* 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;
+ }
+
+* Experimental report features
+Decide whether they should be enabled, or optional. For instance, on:
+
+ input:
+ exp
+ | input exp
+ ;
+
+ exp:
+ token1 "1"
+ | token2 "2"
+ | token3 "3"
+ ;
+
+ token1: token;
+ token2: token;
+ token3: token;
+
+the traditional Bison reports:
+
+ state 0
+
+ $axiom -> . input $ (rule 0)
+
+ token shift, and go to state 1
+
+ input go to state 2
+ exp go to state 3
+ token1 go to state 4
+ token2 go to state 5
+ token3 go to state 6
+
+ state 1
+
+ token1 -> token . (rule 6)
+ token2 -> token . (rule 7)
+ token3 -> token . (rule 8)
+
+ "2" reduce using rule 7 (token2)
+ "3" reduce using rule 8 (token3)
+ $default reduce using rule 6 (token1)
+
+while with --trace, i.e., when enabling both the display of non-core
+item sets and the display of lookaheads, Bison now displays:
+
+ state 0
+
+ $axiom -> . input $ (rule 0)
+ input -> . exp (rule 1)
+ input -> . input exp (rule 2)
+ exp -> . token1 "1" (rule 3)
+ exp -> . token2 "2" (rule 4)
+ exp -> . token3 "3" (rule 5)
+ token1 -> . token (rule 6)
+ token2 -> . token (rule 7)
+ token3 -> . token (rule 8)
+
+ token shift, and go to state 1
+
+ input go to state 2
+ exp go to state 3
+ token1 go to state 4
+ token2 go to state 5
+ token3 go to state 6
+
+ state 1
+
+ token1 -> token . ["1"] (rule 6)
+ token2 -> token . ["2"] (rule 7)
+ token3 -> token . ["3"] (rule 8)
+
+ "2" reduce using rule 7 (token2)
+ "3" reduce using rule 8 (token3)
+ $default reduce using rule 6 (token1)
+
+so decide whether this should be an option, or always enabled. I'm in
+favor of making it the default, but maybe we should tune the output to
+distinguish core item sets from non core:
+
+ state 0
+ Core:
+ $axiom -> . input $ (rule 0)
+
+ Derived:
+ input -> . exp (rule 1)
+ input -> . input exp (rule 2)
+ exp -> . token1 "1" (rule 3)
+ exp -> . token2 "2" (rule 4)
+ exp -> . token3 "3" (rule 5)
+ token1 -> . token (rule 6)
+ token2 -> . token (rule 7)
+ token3 -> . token (rule 8)
+
+ token shift, and go to state 1
+
+ input go to state 2
+ exp go to state 3
+ token1 go to state 4
+ token2 go to state 5
+ token3 go to state 6
+
+
+Note that the same questions applies to --graph.
+
+* Coding system independence
+Paul notes:
+
+ Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is
+ 255). It also assumes that the 8-bit character encoding is
+ the same for the invocation of 'bison' as it is for the
+ invocation of 'cc', but this is not necessarily true when
+ people run bison on an ASCII host and then use cc on an EBCDIC
+ host. I don't think these topics are worth our time
+ addressing (unless we find a gung-ho volunteer for EBCDIC or
+ PDP-10 ports :-) but they should probably be documented
+ somewhere.
+
+* Output directory
+Akim:
+
+| I consider this to be a bug in bison:
+|
+| /tmp % mkdir src
+| /tmp % cp ~/src/bison/tests/calc.y src
+| /tmp % mkdir build && cd build
+| /tmp/build % bison ../src/calc.y
+| /tmp/build % cd ..
+| /tmp % ls -l build src
+| build:
+| total 0
+|
+| src:
+| total 32
+| -rw-r--r-- 1 akim lrde 27553 oct 2 16:31 calc.tab.c
+| -rw-r--r-- 1 akim lrde 3335 oct 2 16:31 calc.y
+|
+|
+| Would it be safe to change this behavior to something more reasonable?
+| Do you think some people depend upon this?
+
+Jim:
+
+Is it that behavior documented?
+If so, then it's probably not reasonable to change it.
+I've Cc'd the automake list, because some of automake's
+rules use bison through $(YACC) -- though I'll bet they
+all use it in yacc-compatible mode.
+
+Pavel:
+
+Hello, Jim and others!
+
+> Is it that behavior documented?
+> If so, then it's probably not reasonable to change it.
+> I've Cc'd the automake list, because some of automake's
+> rules use bison through $(YACC) -- though I'll bet they
+> all use it in yacc-compatible mode.
+
+Yes, Automake currently used bison in Automake-compatible mode, but it
+would be fair for Automake to switch to the native mode as long as the
+processed files are distributed and "missing" emulates bison.
+
+In any case, the makefiles should specify the output file explicitly
+instead of relying on weird defaults.
+
+> | src:
+> | total 32
+> | -rw-r--r-- 1 akim lrde 27553 oct 2 16:31 calc.tab.c
+> | -rw-r--r-- 1 akim lrde 3335 oct 2 16:31 calc.y
+
+This is not _that_ ugly as it seems - with Automake you want to put
+sources where they belong - to the source directory.
+
+> | This is not _that_ ugly as it seems - with Automake you want to put
+> | sources where they belong - to the source directory.
+>
+> The difference source/build you are referring to is based on Automake
+> concepts. They have no sense at all for tools such as bison or gcc
+> etc. They have input and output. I do not want them to try to grasp
+> source/build. I want them to behave uniformly: output *here*.
+
+I realize that.
+
+It's unfortunate that the native mode of Bison behaves in a less uniform
+way than the yacc mode. I agree with your point. Bison maintainters may
+want to fix it along with the documentation.
+
+
* Unit rules
Maybe we could expand unit rules, i.e., transform
when there are no actions. This can significantly speed up some
grammars.
-* Huge Grammars
-Currently, not only is Bison unable to handle huge grammars because of
-internal limitations (see test `big triangle'). Push the limit beyond
-253. Be my guest: fix this!
+* Stupid error messages
+An example shows it easily:
+
+src/bison/tests % ./testsuite -k calc,location,error-verbose -l
+GNU Bison 1.49a test suite test groups:
+
+ NUM: FILENAME:LINE TEST-GROUP-NAME
+ KEYWORDS
+
+ 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 '('
+
+* yyerror, yyprint 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...
* 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.
-* NEWS
-Sort from 1.31 NEWS.
-
-* Prologue
-The %union is declared after the user C declarations. It can be
-a problem if YYSTYPE is declared after the user part. []
-
-Actually, the real problem seems that the %union ought to be output
-where it was defined. For instance, in gettext/intl/plural.y, we
-have:
+* Memory leaks in the generator
+A round of memory leak clean ups would be most welcome. Dmalloc,
+Checker GCC, Electric Fence, or Valgrind: you chose your tool.
- %{
- ...
- #include "gettextP.h"
- ...
- %}
-
- %union {
- unsigned long int num;
- enum operator op;
- struct expression *exp;
- }
-
- %{
- ...
- static int yylex PARAMS ((YYSTYPE *lval, const char **pexp));
- ...
- %}
-
-Where the first part defines struct expression, the second uses it to
-define YYSTYPE, and the last uses YYSTYPE. Only this order is valid.
+* Memory leaks in the parser
+The same applies to the generated parsers. In particular, this is
+critical for user data: when aborting a parsing, when handling the
+error token etc., we often throw away yylval without giving a chance
+of cleaning it up to the user.
* --graph
Show reductions. []
** %no-lines [ok]
** %no-parser []
** %pure-parser []
-** %semantic-parser []
** %token-table []
** Options which could use parse_dquoted_param ().
Maybe transfered in lex.c.
* input synclines
Some users create their foo.y files, and equip them with #line. Bison
should recognize these, and preserve them.
+
+* BTYacc
+See if we can integrate backtracking in Bison. Contact the BTYacc
+maintainers.
+
+* Automaton report
+Display more clearly the lookaheads for each item.
+
+* RR conflicts
+See if we can use precedence between rules to solve RR conflicts. See
+what POSIX says.
+
+* Precedence
+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.
+
+This will be possible with a Bison parser for the grammar, as it will
+make it much easier to extend the grammar.
+
+* Parsing grammars
+Rewrite the reader in Flex/Bison. There will be delicate parts, in
+particular, expect the scanner to be hard to write. Many interesting
+features cannot be implemented without such a new reader.
+
+* Presentation of the report file
+From: "Baum, Nathan I" <s0009525@chelt.ac.uk>
+Subject: Token Alias Bug
+To: "'bug-bison@gnu.org'" <bug-bison@gnu.org>
+
+I've also noticed something, that whilst not *wrong*, is inconvienient: I
+use the verbose mode to help find the causes of unresolved shift/reduce
+conflicts. However, this mode insists on starting the .output file with a
+list of *resolved* conflicts, something I find quite useless. Might it be
+possible to define a -v mode, and a -vv mode -- Where the -vv mode shows
+everything, but the -v mode only tells you what you need for examining
+conflicts? (Or, perhaps, a "*** This state has N conflicts ***" marker above
+each state with conflicts.)
+
+* $undefined
+From Hans:
+- If the Bison generated parser experiences an undefined number in the
+character range, that character is written out in diagnostic messages, an
+addition to the $undefined value.
+
+Suggest: Change the name $undefined to undefined; looks better in outputs.
+
+* Default Action
+From Hans:
+- For use with my C++ parser, I transported the "switch (yyn)" statement
+that Bison writes to the bison.simple skeleton file. This way, I can remove
+the current default rule $$ = $1 implementation, which causes a double
+assignment to $$ which may not be OK under C++, replacing it with a
+"default:" part within the switch statement.
+
+Note that the default rule $$ = $1, when typed, is perfectly OK under C,
+but in the C++ implementation I made, this rule is different from
+$<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).
+
+Note: Robert Anisko handles this. He knows how to do it.
+
+* Documenting C++ output
+Write a first documentation for C++ output.
+
+* 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
+To: bug-bison@gnu.org
+X-Sent: 1 week, 4 days, 14 hours, 38 minutes, 11 seconds ago
+
+The other day I had the need for explicitly building the parse tree. I
+used %locations for that and defined YYLLOC_DEFAULT to call a function
+that returns the tree node for the production. Easy. But I also needed
+to assign the S-attribute to the tree node. That cannot be done in
+YYLLOC_DEFAULT, because it is invoked before the action is executed.
+The way I solved this was to define a macro YYACT_EPILOGUE that would
+be invoked after the action. For reasons of symmetry I also added
+YYACT_PROLOGUE. Although I had no use for that I can envision how it
+might come in handy for debugging purposes.
+All is needed is to add
+
+#if YYLSP_NEEDED
+ YYACT_EPILOGUE (yyval, (yyvsp - yylen), yylen, yyloc, (yylsp - yylen));
+#else
+ YYACT_EPILOGUE (yyval, (yyvsp - yylen), yylen);
+#endif
+
+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.
+
+-----
+
+Copyright (C) 2001, 2002 Free Software Foundation, Inc.
+
+This file is part of GNU Autoconf.
+
+GNU Autoconf 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.
+
+GNU Autoconf is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
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+
+You should have received a copy of the GNU General Public License
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+Boston, MA 02111-1307, USA.
projects / bison.git / blobdiff