X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/8b3ba7ff05c1f293e168d2762580a5326c0aab1a..c0ad8bf3c2fb46f001bb24ac98a72b8bfb3a77ce:/TODO?ds=sidebyside diff --git a/TODO b/TODO index 01e1a081..ad99639d 100644 --- a/TODO +++ b/TODO @@ -1,119 +1,146 @@ -*- outline -*- -* Coding system independence -Paul notes: +* Header guards - 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. +En rentrant chez moi, je relance un `make' sur un projet que j'ai avancé +ailleurs durant la semaine. Le système que j'utilise ici est un peu plus +à jour que l'autre, et le Bison est probablement plus récent itou. Ici, +c'est la version 1.33. J'obtiens, en montrant un peu plus que nécessaire: + +----------------------------------------------------------------------> +cd ~/fpub/pyrexpp/Pyrexpp/ +LANGUAGE= /usr/bin/make MAKEFLAGS='-k -j2' +/usr/bin/make -C .. install +make[1]: Entre dans le répertoire `/bpi/titan/home/pinard/fpub/pyrexpp' +install -g bpi -m 2775 -d Prépare-titan +chmod g+sw Prépare-titan +touch Prépare-titan/.estampille +/usr/bin/gcc -fPIC -I/usr/include/python2.2 -IPrépare-titan -g -c -o Prépare-titan/ctools.o ctools.c +bison -d -o Prépare-titan/c-parser.c c-parser.y +/usr/bin/gcc -fPIC -I/usr/include/python2.2 -IPrépare-titan -g -c -o Prépare-titan/c-parser.o Prépare-titan/c-parser.c +flex -t c-scanner.l | grep -v '^#line' > Prépare-titan/c-scanner.c +/usr/bin/gcc -fPIC -I/usr/include/python2.2 -IPrépare-titan -g -c -o Prépare-titan/c-scanner.o Prépare-titan/c-scanner.c +In file included from Prépare-titan/c-scanner.c:547: +Prépare-titan/c-parser.h:1: warning: garbage at end of `#ifndef' argument +Prépare-titan/c-parser.h:2: warning: missing white space after `#define BISON_PR' +/usr/bin/gcc -o Prépare-titan/ctools.so Prépare-titan/ctools.o Prépare-titan/c-scanner.o -shared -lm +python setup.py --quiet build +install -g bpi -m 664 Prépare-titan/ctools.so /bpi/titan/local/lib/python2.2/site-packages/Pyrexpp +python setup.py --quiet install +make[1]: Quitte le répertoire `/bpi/titan/home/pinard/fpub/pyrexpp' +[...] +----------------------------------------------------------------------< + +Diagnostics que je n'avais sûrement pas, plus tôt en journée, sur l'autre +système. En allant voir, je trouve: + +----------------------------------------------------------------------> +#ifndef BISON_PRÉPARE_TITAN_C_PARSER_H +# define BISON_PRÉPARE_TITAN_C_PARSER_H + +# ifndef YYSTYPE +# define YYSTYPE int +# endif +# define IDENTIFIER 257 +[...] + +extern YYSTYPE yylval; + +#endif /* not BISON_PRÉPARE_TITAN_C_PARSER_H */ +----------------------------------------------------------------------< + +Le pré-processeur de C n'est pas à l'aise avec les caractères accentués +dans les identificateurs. + +Bon, de mon expérience, il n'a jamais été nécessaire de protéger un fichier +`.h' de Bison ou Yacc contre de multiples inclusions, mais si ça été +fait, je présume qu'il y avait un problème réel et convaincant à régler, +et qu'il ne s'agit pas d'une simple fantaisie: je ne mettrai donc pas +ça en doute. Mais le choix du nom de l'identificateur laisse à désirer, +tu en conviendras :-). Et faut-il vraiment y inclure le répertoire? + + +* URGENT: Documenting C++ output +Write a first documentation for C++ output. + + +* 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 -* Using enums instead of int for tokens. -Paul suggests: - - #ifndef YYTOKENTYPE - # if defined (__STDC__) || defined (__cplusplus) - /* Put the tokens into the symbol table, so that GDB and other debuggers - know about them. */ - enum yytokentype { - FOO = 256, - BAR, - ... - }; - /* POSIX requires `int' for tokens in interfaces. */ - # define YYTOKENTYPE int - # endif - #endif - #define FOO 256 - #define BAR 257 - ... - -> I'm in favor of -> -> %token FOO 256 -> %token BAR 257 -> -> and Bison moves error into 258. - -Yes, I think that's a valid extension too, if the user doesn't define -the token number for error. - -* 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. +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? + + +* 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 +part of $default. Should we make the two reductions explicit, or just +keep $default? See the following point. + +** Disabled Reductions +See `tests/conflicts.at (Defaulted Conflicted Reduction)', and decide +what we want to do. + +** Documentation +Extend with error productions. The hard part will probably be finding +the right rule so that a single state does not exhibit too many yet +undocumented ``features''. Maybe an empty action ought to be +presented too. Shall we try to make a single grammar with all these +features, or should we have several very small grammars? + +** --report=conflict-path +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. + + +* 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... + +** 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; + } + * Unit rules Maybe we could expand unit rules, i.e., transform @@ -126,77 +153,44 @@ into exp: exp '+' exp | exp '&' exp; when there are no actions. This can significantly speed up some -grammars. - -* 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 '(' +grammars. I can't find the papers. In particular the book `LR +parsing: Theory and Practice' is impossible to find, but according to +`Parsing Techniques: a Practical Guide', it includes information about +this issue. Does anybody have it? -* 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. -* 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. - -* 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. - -* 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: - - %{ - ... - #include "gettextP.h" - ... - %} - - %union { - unsigned long int num; - enum operator op; - struct expression *exp; - } - %{ - ... - static int yylex PARAMS ((YYSTYPE *lval, const char **pexp)); - ... - %} +* Documentation + +** History/Bibliography +Some history of Bison and some bibliography would be most welcome. +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: + + 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. + -Where the first part defines struct expression, the second uses it to -define YYSTYPE, and the last uses YYSTYPE. Only this order is valid. * --graph Show reductions. [] @@ -205,10 +199,9 @@ 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. +Maybe transferred in lex.c. *** %skeleton [ok] *** %output [] *** %file-prefix [] @@ -225,7 +218,7 @@ Find the best graph parameters. [] * doc/bison.texinfo ** Update informations about ERROR_VERBOSE. [] -** Add explainations about +** Add explanations about skeleton muscles. [] %skeleton. [] @@ -233,59 +226,6 @@ skeleton muscles. [] ** tests/pure-parser.at [] New tests. -* Debugging parsers - -From Greg McGary: - -akim demaille writes: - -> With great pleasure! Nonetheless, things which are debatable -> (or not, but just `big') should be discuss in `public': something -> like help- or bug-bison@gnu.org is just fine. Jesse and I are there, -> but there is also Jim and some other people. - -I have no idea whether it qualifies as big or controversial, so I'll -just summarize for you. I proposed this change years ago and was -surprised that it was met with utter indifference! - -This debug feature is for the programs/grammars one develops with -bison, not for debugging bison itself. I find that the YYDEBUG -output comes in a very inconvenient format for my purposes. -When debugging gcc, for instance, what I want is to see a trace of -the sequence of reductions and the line#s for the semantic actions -so I can follow what's happening. Single-step in gdb doesn't cut it -because to move from one semantic action to the next takes you through -lots of internal machinery of the parser, which is uninteresting. - -The change I made was to the format of the debug output, so that it -comes out in the format of C error messages, digestible by emacs -compile mode, like so: - -grammar.y:1234: foo: bar(0x123456) baz(0x345678) - -where "foo: bar baz" is the reduction rule, whose semantic action -appears on line 1234 of the bison grammar file grammar.y. The hex -numbers on the rhs tokens are the parse-stack values associated with -those tokens. Of course, yytype might be something totally -incompatible with that representation, but for the most part, yytype -values are single words (scalars or pointers). In the case of gcc, -they're most often pointers to tree nodes. Come to think of it, the -right thing to do is to make the printing of stack values be -user-definable. It would also be useful to include the filename & -line# of the file being parsed, but the main filename & line# should -continue to be that of grammar.y - -Anyway, this feature has saved my life on numerous occasions. The way -I customarily use it is to first run bison with the traces on, isolate -the sequence of reductions that interests me, put those traces in a -buffer and force it into compile-mode, then visit each of those lines -in the grammar and set breakpoints with C-x SPACE. Then, I can run -again under the control of gdb and stop at each semantic action. -With the hex addresses of tree nodes, I can inspect the values -associated with any rhs token. - -You like? - * input synclines Some users create their foo.y files, and equip them with #line. Bison should recognize these, and preserve them. @@ -294,38 +234,133 @@ should recognize these, and preserve them. See if we can integrate backtracking in Bison. Contact the BTYacc maintainers. -* Automaton report -Display more clearly the lookaheads for each item. +** 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 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. + +** Adjust the skeletons +Import the skeletons for C and C++. + +** Improve the skeletons +Have them support yysymprint, yydestruct and so forth. -* RR conflicts -See if we can use precedence between rules to solve RR conflicts. See -what POSIX says. * Precedence + +** Partial order 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. +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. + + +* $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 $$ = $1, when typed, is perfectly OK under C, +but in the C++ implementation I made, this rule is different from +$$ = $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 +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. -* Parsing grammars -Rewrite the reader in Bison. +* 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. ----- Copyright (C) 2001, 2002 Free Software Foundation, Inc. -This file is part of GNU Autoconf. +This file is part of GNU Bison. -GNU Autoconf is free software; you can redistribute it and/or modify +GNU Bison 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, +GNU Bison 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 autoconf; see the file COPYING. If not, write to +along with Bison; see the file COPYING. 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