- Annonce

[Seminaire-LRDE] Mercredi 13 novembre 2013: Dodji Seketeli, Red Hat
by Daniela Becker 24 Oct '13

24 Oct '13

Chers collègues, La prochaine session du séminaire Performance et Généricité du LRDE (Laboratoire de Recherche et Développement de l'EPITA) aura lieu le Mercredi 13 novembre 2013 (11h--12h30), Salle Lα du LRDE. Au programme: * 11h-12h30: Address & Thread Sanitizer in GCC: Etat Actuel et Orientation Future -- Dodji Seketeli, Red Hat http://gcc.gnu.org Address & Thread sanitizer sont des outils destinés à détecter les erreurs d'accès à la mémoire ainsi que les erreurs d'accès concurrents en environnement multi-threads. Ces outils sont constitués de deux parties logiques distinctes: une partie instrumentant le code généré de manière statique, et un environnement d'exécution. Cet exposé présente l'implémentation de Address & Thread Sanitizer dans GCC, les principes de fonctionnement de l'environnement d'exécution de ces deux outils ainsi que les futures directions du projet. -- Dodji Seketeli est ingénieur dans l'équipe Tools de Red Hat. Il travaille sur la suite des compilateurs GNU, principalement sur les compilateurs C et C++. Pendant son temps libre, lorsqu'il ne joue pas avec son épouse et ses enfants, il maintient Nemiver, le debuggeur graphique du projet d'environnement de bureau libre GNOME. En dehors des logiciels libres, il s'intéresse aux arts martiaux et à l'histoire. Pour plus de renseignements, consultez http://seminaire.lrde.epita.fr/. L'entrée du séminaire est libre. Merci de bien vouloir diffuser cette information le plus largement possible. -- Akim Demaille Akim.Demaille(a)lrde.epita.fr _______________________________________________ Seminaire mailing list Seminaire(a)lrde.epita.fr https://lists.lrde.epita.fr/listinfo/seminaire

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Re: [Lrde Annonce] New publication: LPAR'13
by Etienne Renault 09 Oct '13

09 Oct '13

We are pleased to inform you that the following paper has been accepted in the 19th International Conference on Logic for Programming, Artificial Intelligence, and Reasoning (LPAR). Please find the title and abstract below. Title and corresponding authors: "Three SCC-based Emptiness Checks for Generalized Büchi Automata" E. Renault(1), A. Duret-Lutz(1), F. Kordon(2), and D. Poitrenaud(2) (1) LRDE-EPITA, www.lrde.epita.fr (2) UPMC-LIP6, www.lip6.fr Abstract: The automata-theoretic approach for the verification of linear time properties involves checking the emptiness of a Büchi automaton. However generalized Büchi automata, with multiple acceptance sets, are preferred when verifying under weak fairness hypotheses. Existing emptiness checks for which the complexity is independent of the number of acceptance sets are all based on the enumeration of Strongly Connected Components (SCCs). In this paper, we review the state of the art SCC enumeration algorithms to study how they can be turned into emptiness checks. This leads us to define two new emptiness check algorithms (one of them based on the Union Find data structure), introduce new optimizations, and show that one of these can be of benefit to a classic SCCs enumeration algorithm. We have implemented all these variants to compare their relative performances and the overhead induced by the emptiness check compared to the corresponding SCCs enumeration algorithm. Our experiments shows that these three algorithms are comparable.

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Spot 1.2 has been released
by Alexandre Duret-Lutz 01 Oct '13

01 Oct '13

I'm very pleased to announce the release of Spot 1.2. Spot is a model-checking library developed collaboratively by LRDE and LIP6. It provides algorithms and data structures to implement the automata-theoretic approach to LTL model checking. This release contains several new features (summarized below), but the most notable are the interface with ltl2dstar (i.e., Spot can read deterministic Rabin and Streett automata and convert them into Büchi automata) and algorithms for minimizing deterministic TGBA or BA using a SAT-solver. You can find the new release here: http://spot.lip6.fr/dl/spot-1.2.tar.gz Please report any issue to <spot(a)lrde.epita.fr>. New in spot 1.2 (2013-10-01) * Changes to command-line tools: - ltlcross has a new option --color to color its output. It is enabled by default when the output is a terminal. - ltlcross will give an example of infinite word accepted by the two automata when the product between a positive automaton and a negative automaton is non-empty. - ltlcross can now read the Rabin and Streett automata output by ltl2dstar. This type of output should be specified using '%D': ltlcross 'ltl2dstar --ltl2nba=spin:path/to/ltl2tgba@-s %L %D' However because Spot only supports Büchi acceptance, these Rabin and Streett automata are immediately converted to TGBAs before further processing by ltlcross. This is still interesting to search for bugs in translators to Rabin or Streett automata, but the statistics (of the resulting TGBAs) might not be very relevant. - When ltlcross obtains a deterministic automaton from a translator it will now complement this automaton to perform additional intersection checks. This is complementation is done only for deterministic automata (because that is cheap) and can be disabled with --no-complement. - To help with debugging problems detected by ltlcross, the environment variables SPOT_TMPDIR and SPOT_TMPKEEP control where temporary files are created and if they should be erased. Read the man page of ltlcross for details. - There is a new command, named dstar2tgba, that converts a deterministic Rabin or Streett automaton (expressed in the output format of ltl2dstar) into a TGBA, BA or Monitor. In the case of Rabin acceptance, the conversion will output a deterministic Büchi automaton if one such automaton exist. Even if no such automaton exists, the conversion will actually preserves the determinism of any SCC that can be kept deterministic. In the case of Streett acceptance, the conversion produces non-deterministic Büchi automata with Generalized acceptance. These are then degeneralized if requested. See http://spot.lip6.fr/userdoc/dstar2tgba.html for some examples, and the man page for more reference. - The %S escape sequence used by ltl2tgba --stats to display the number of SCCs in the output automaton has been renamed to %c. This makes it more homogeneous with the --stats option of the new dstar2tgba command. Additionally, the %p escape can now be used to show whether the output automaton is complete, and the %r escape will give the number of seconds spent building the output automaton (excluding the time spent parsing the input). - ltl2tgba, ltl2tgta, and dstar2tgba have a --complete option to output complete automata. - ltl2tgba, ltl2tgta, and dstar2tgba can use a SAT-solver to minimize deterministic automata. Doing so is only needed on properties that are stronger than obligations (for obligations our WDBA-minimization procedure will return a minimimal deterministic automaton more efficiently) and is disabled by default. See the spot-x(7) man page for documentation about the related options: sat-minimize, sat-states, sat-acc, state-based. See also http://spot.lip6.fr/userdoc/satmin.html for some examples. - ltlfilt, genltl, and randltl now have a --latex option to output formulas in a way that its easier to embed in a LaTeX document. Each operator is output as a command such as \U, \F, etc. doc/tl/spotltl.sty gives one possible definition for each macro. - ltlfilt, genltl, and randltl have a new --format option to indicate how to present the output formula, possibly with information about the input. - ltlfilt as a new option, --relabel-bool, to abstract independent Boolean subformulae as if they were atomic propositions. For instance "a & GF(c | d) & b & X(c | d)" would be rewritten as "p0 & GF(p1) & Xp1". * New functions and classes in the library: - dtba_sat_synthetize(): Use a SAT-solver to build an equivalent deterministic TBA with a fixed number of states. - dtba_sat_minimize(), dtba_sat_minimize_dichotomy(): Iterate dtba_sat_synthetize() to reduce the number of states of a TBA. - dtgba_sat_synthetize(), dtgba_sat_minimize(), dtgba_sat_minimize_dichotomy(): Likewise, for deterministic TGBA. - is_complete(): Check whether a TGBA is complete. - tgba_complete(): Complete an automaton by adding a sink state if needed. - dtgba_complement(): Complement a deterministic TGBA. - satsolver(): Run an (external) SAT solver, honoring the SPOT_SATSOLVER environment variable if set. - tba_determinize(): Run a power-set construction, and attempt to fix the acceptance simulation to build a deterministic TBA. - dstar_parse(): Read a Streett or Rabin automaton in ltl2dstar's format. Note that this format allows only deterministic automata. - nra_to_nba(): Convert a (possibly non-deterministic) Rabin automaton to a non-deterministic Büchi automaton. - dra_to_ba(): Convert a deterministic Rabin automaton to a Büchi automaton, preserving acceptance in all SCCs where this is possible. - nsa_to_tgba(): Convert a (possibly non-deterministic) Streett automaton to a non-deterministic TGBA. - dstar_to_tgba(): Convert any automaton returned by dstar_parse() into a TGBA. - build_tgba_mask_keep(): Build a masked TGBA that shows only a subset of states of another TGBA. - build_tgba_mask_ignore(): Build a masked TGBA that ignore a subset of states of another TGBA. - class tgba_proxy: Helps writing on-the-fly algorithms that delegate most of their methods to the original automaton. - class bitvect: A dynamic bit vector implementation. - class word: An infinite word, stored as prefix + cycle, with a simplify() methods to simplify cycle and prefix in obvious ways. - class temporary_file: A temporary file. Can be instanciated with create_tmp_file() or create_open_tmpfile(). - count_state(): Return the number of states of a TGBA. Implement a couple of specializations for classes where is can be know without exploration. - to_latex_string(): Output a formula using LaTeX syntax. - relabel_bse(): Relabeling of Boolean Sub-Expressions. Implements ltlfilt's --relabel-bool option describe above. * Noteworthy internal changes: - When minimize_obligation() is not given the formula associated to the input automaton, but that automaton is deterministic, it can still attempt to call minimize_wdba() and check the correcteness using dtgba_complement(). This allows dstar2tgba to apply WDBA-minimization on deterministic Rabin automata. - tgba_reachable_iterator_depth_first has been redesigned to effectively perform a DFS. As a consequence, it does not inherit from tgba_reachable_iterator anymore. - postproc::set_pref() was used to accept an argument among Any, Small or Deterministic. These can now be combined with Complete as Any|Complete, Small|Complete, or Deterministic|Complete. - operands of n-ary operators (like & and |) are now ordered so that Boolean terms come first. This speeds up syntactic implication checks slightly. Also, literals are now sorted using strverscmp(), so that p5 comes before p12. - Syntactic implication checks have been generalized slightly (for instance 'a & b & F(a & b)' is now reduced to 'a & b' while it was not changed in previous versions). - All the parsers implemented in Spot now use the same type to store locations. - Cleanup of exported symbols All symbols in the library now have hidden visibility on ELF systems. Public classes and functions have been marked explicitely for export with the SPOT_API macro. During this massive update, some of functions that should not have been made public in the first place have been moved away so that they can only be used from the library. Some old of unused functions have been removed. removed: - class loopless_modular_mixed_radix_gray_code hidden: - class acc_compl - class acceptance_convertor - class bdd_allocator - class free_list * Bug fixes: - Degeneralization was not indempotant on automata with an accepting initial state that was on a cycle, but without self-loop. - Configuring with --enable-optimization would reset the value of CXXFLAGS. -- Alexandre Duret-Lutz

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Keynote at ACCU 2014
by Didier Verna 23 Sep '13

23 Sep '13

Hello, I am pleased to announce that I will be a keynote speaker at the next ACCU conference, to be held in Bristol, next April. The title and abstract are given below. Biological Realms in Computer Science In biology, evolution is usually seen as a tinkering process, different from what an engineer does when he plans the development of his systems. Recently, studies have shown that even in biology, there is a part of good engineering. As computer scientists, we have much more difficulty to admit that there is also a great deal of tinkering in what we do, and that our software systems behave more and more like biological realms every day. This keynote will take you to a journey through the bonds between biology and computer science. Starting with an epistemological and historical view, we will see how these bonds developed over the years, but we will also ask ourselves whether these bonds were intentionally created, or whether they already existed, before we even found them. We will also meet the Engineer and the Tinkerer, and see that they are not necessarily different persons. Finally, through such notions as Determinism, Predictability and Control, we will envision and explain a possible future for our software systems seen as living organisms; a future that's in fact already here, but that we are reluctant to accept. -- Resistance is futile. You will be jazzimilated. Lisp, Jazz, Aïkido: http://www.didierverna.info

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L'air de rien 29.0
by Daniela Becker 18 Sep '13

18 Sep '13

Bonjour, nous avons le plaisir de vous annoncer la sortie du n°29 du bulletin du LRDE. C'est un numéro Spécial Rentrée qui présente l'ensemble des membres du LRDE. Vous y trouverez également un aperçu des activités du LRDE et de la majeure CSI dont font partie tous les élèves épitéens intégrant le labo. Vous pouvez télécharger le bulletin en couleur à la page suivante : http://publis.lrde.epita.fr/201309-l-air-de-rien-29 -- Daniela Becker Responsable administrative du LRDE

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Vidéo du séminaire CSI de Raphaël Boissel du 11 juillet 2013 en ligne
by Daniela Becker 10 Sep '13

10 Sep '13

Bonjour, nous avons le plaisir de vous présenter la vidéo de l'exposé de Raphaël Boissel durant le séminaire CSI du 11 juillet 2013. Vous la trouverez ici : http://www.dailymotion.com/video/k6zPvJ45FyX2c84BqYT Le résumé de l'exposé : *************************** " Réduire les ressources utilisées par une chaîne de traitement complexe " - Raphaël Boissel Même si la précision du système de localisation de texte développé par le laboratoire a aujourd'hui grandement augmentée, un des principaux problèmes demeure la vitesse. En effet, si l'on souhaite être en mesure de l'utiliser pour extraire du texte dans des vidéos ou s'il doit être embarqué dans des appareils aux ressources limitées tel que des téléphones portables, la consommation de ressources mémoire et CPU doit être réduite. Pour parvenir à cet objectif, plusieurs méthodes permettant de réduire l'impact mémoire et CPU des étapes les plus coûteuses peuvent être utilisées. Cependant, toutes n'offrent pas les mêmes résultats en fonction de l'image d'entrée et certaines peuvent même dégrader le résultat final produit par le système. L'objectif est de présenter ces méthodes, d'observer leurs résultats et de déterminer dans quelles situations elles sont applicables. -- Daniela Becker Responsable administrative du LRDE

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[Seminaire-LRDE] Mercredi 9 octobre 2013: Luca Saiu -- Projet GNU, INRIA.
by Daniela Becker 04 Sep '13

04 Sep '13

Chers collègues, La prochaine session du séminaire Performance et Généricité du LRDE (Laboratoire de Recherche et Développement de l'EPITA) aura lieu le Mercredi 9 octobre 2013 (11h--12h), Salle Lα du LRDE. Au programme: * 11h: GNU epsilon, un langage de programmation extensible -- Luca Saiu -- Projet GNU, INRIA. http://ageinghacker.net Le réductionnisme est une technique réaliste de conception et implantation de vrais langages de programmation, et conduit à des solutions plus faciles à étendre, expérimenter et analyser. Je vais décrire la conception et l'implantation de GNU epsilon, un langage de programmation extensible, basé sur un langage-noyau minimaliste impératif du premier ordre, équipé de mécanismes d'abstraction forts et avec des possibilités de réflexion et auto-modification. Le langage peut être étendu à des niveaux très hauts : en utilisant des macros à la Lisp et des transformations de code à code réécrivant les expressions étendues en expressions-noyau, on arrive à ajouter les clôtures et les continuations de première classe au dessus du noyau. Les programmes qui ne s'auto-modifient pas peuvent être analysés formellement, grâce à la simplicité de la sémantique. Je vais parler rapidement d'une analyse statique dont j'ai prouvé une propriété de «soundness» par rapport à la sémantique dynamique. Le langage se prête à une implantation efficace : je vais montrer un prototype de compilateur natif particulièrement simple. -- Luca Saiu, programmeur expérimenté et spécialiste de langages, a obtenu son master à l'Université de Pise et son doctorat à l'Université Paris 13. Il a travaillé à l'INRIA sur le support multi-cœur d'OCaml. Le langage de programmation epsilon, logiciel GNU, est son projet le plus ambitieux. Luca Saiu est également co-auteur de Marionnet, un simulateur de réseaux en OCaml, utilisé pour la pédagogie en France et à l'étranger. Pour plus de renseignements, consultez http://seminaire.lrde.epita.fr/. L'entrée du séminaire est libre. Merci de bien vouloir diffuser cette information le plus largement possible. -- Akim Demaille Akim.Demaille(a)lrde.epita.fr _______________________________________________ Seminaire mailing list Seminaire(a)lrde.epita.fr https://lists.lrde.epita.fr/listinfo/seminaire

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Declt 1.0 is out
by Didier Verna 26 Aug '13

26 Aug '13

I'm pleased to announce the release of Declt 1.0, the first officially stable version[1]. Declt (pronounce "dec'let") is a reference manual generator for Common Lisp libraries. It works by loading an ASDF system and introspecting its contents. The generated documentation contains the description for the system itself and its components (modules and files), the packages defined in that system and the definitions found in those packages. Exported and internal definitions are listed separately. This allows the reader to have a quick view on the library's public API. Within each section, definitions are sorted lexicographically. In addition to ASDF system components and packages, Declt documents the following definitions: constants, special variables, symbol macros, macros, setf expanders, compiler macros, functions (including setf ones), generic functions and methods (including setf ones), method combinations, conditions, structures, classes and types. The generated documentation includes every possible bit of information that introspecting can provide: documentation strings, lambda lists (including qualifiers and specializers where appropriate), slots (including type, allocation and initialization arguments), definition source file etc. Every documented item provides a full set of cross-references to related items: ASDF component dependencies, parents and children, classes direct methods, super and subclasses, slot readers and writers, setf expanders access and update functions etc. Finally, Declt produces exhaustive and multiple-entry indexes for every documented item. Reference manuals are generated in Texinfo format (compatible, but not requiring Texinfo 5). From there it is possible to produce readable / printable output in info, HTML, PDF, DVI and PostScript with tools such as makeinfo, texi2dvi or texi2pdf. The Declt reference manual is the primary example of documentation generated by Declt itself. Footnotes: [1] http://www.lrde.epita.fr/~didier/software/lisp/misc.php#declt -- Resistance is futile. You will be jazzimilated. Lisp, Jazz, Aïkido: http://www.didierverna.info

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Talks at TUG 2013
by Didier Verna 22 Aug '13

22 Aug '13

Hello, I am pleased to announce that I will give 2 talks at the next Tex Users Group conference, to be held in Tokyo, Japan, next October. Please find the abstracts below. TiCL: The prototype Last year, I presented some ideas about using one of the oldest programming language (Lisp), in order to modernize one of the oldest typesetting systems (TeX). This talk was mostly focused on justifying the technical fitness of Lisp for this task. This time, I would like to take the opposite view and demonstrate a prototype, from the user's perspective. This will involve showing what a TiCL document could look like, the implications in terms of typesetting vs. programmatic features, and also in terms of extensibility (relating this to package authoring). The incredible tale of the author who didn't want to do the publisher's job In this talk, I will relate a recent experience of mine: writing a book chapter for a publisher who doesn't have a clue about typesetting. I will confess my futile attempt at using TeX for writing the chapter in question. I will then describe the hell that descended upon me for daring to do that. I will however admit that the hell in question would have been even greater, had I not done so. I will give this talk both crying and laughing, and I will seek your comfort. -- Resistance is futile. You will be jazzimilated. Lisp, Jazz, Aïkido: http://www.didierverna.info

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GNU Bison 3.0
by Akim Demaille 01 Aug '13

01 Aug '13

L'équipe Bison est heureuse d'annoncer la publication de GNU Bison 3.0, qui introduit de nombreuses nouvelles fonctionnalités. GNU Bison est un générateur d'analyseurs syntaxiques dans la lignée de Yacc. Les nouveautés comprennent entre autres : (i) profonde rénovation du système de diagnostiques (erreurs et avertissements), (ii) des moyens plus souples de définition des types des valeurs sémantiques (avec en particulier la possibilité d'utiliser de véritables objets en C++), (iii) une interface "push" pour les parleurs Java, et (iv) des prédicats de filtrage en mode GLR. Certaines de ces nouveautés sont des contributions d'épitéens. http://www.gnu.org/software/bison/ Voici les changements, plus en détails, et plus en anglais. * Noteworthy changes in release 3.0 (2013-07-25) [stable] ** WARNING: Future backward-incompatibilities! Like other GNU packages, Bison will start using some of the C99 features for its own code, especially the definition of variables after statements. The generated C parsers still aim at C90. ** Backward incompatible changes *** Obsolete features Support for YYFAIL is removed (deprecated in Bison 2.4.2): use YYERROR. Support for yystype and yyltype is removed (deprecated in Bison 1.875): use YYSTYPE and YYLTYPE. Support for YYLEX_PARAM and YYPARSE_PARAM is removed (deprecated in Bison 1.875): use %lex-param, %parse-param, or %param. Missing semicolons at the end of actions are no longer added (as announced in the release 2.5). *** Use of YACC='bison -y' TL;DR: With Autoconf <= 2.69, pass -Wno-yacc to (AM_)YFLAGS if you use Bison extensions. Traditional Yacc generates 'y.tab.c' whatever the name of the input file. Therefore Makefiles written for Yacc expect 'y.tab.c' (and possibly 'y.tab.h' and 'y.outout') to be generated from 'foo.y'. To this end, for ages, AC_PROG_YACC, Autoconf's macro to look for an implementation of Yacc, was using Bison as 'bison -y'. While it does ensure compatible output file names, it also enables warnings for incompatibilities with POSIX Yacc. In other words, 'bison -y' triggers warnings for Bison extensions. Autoconf 2.70+ fixes this incompatibility by using YACC='bison -o y.tab.c' (which also generates 'y.tab.h' and 'y.output' when needed). Alternatively, disable Yacc warnings by passing '-Wno-yacc' to your Yacc flags (YFLAGS, or AM_YFLAGS with Automake). ** Bug fixes *** The epilogue is no longer affected by internal #defines (glr.c) The glr.c skeleton uses defines such as #define yylval (yystackp->yyval) in generated code. These weren't properly undefined before the inclusion of the user epilogue, so functions such as the following were butchered by the preprocessor expansion: int yylex (YYSTYPE *yylval); This is fixed: yylval, yynerrs, yychar, and yylloc are now valid identifiers for user-provided variables. *** stdio.h is no longer needed when locations are enabled (yacc.c) Changes in Bison 2.7 introduced a dependency on FILE and fprintf when locations are enabled. This is fixed. *** Warnings about useless %pure-parser/%define api.pure are restored ** Diagnostics reported by Bison Most of these features were contributed by Théophile Ranquet and Victor Santet. *** Carets Version 2.7 introduced caret errors, for a prettier output. These are now activated by default. The old format can still be used by invoking Bison with -fno-caret (or -fnone). Some error messages that reproduced excerpts of the grammar are now using the caret information only. For instance on: %% exp: 'a' | 'a'; Bison 2.7 reports: in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr] in.y:2.12-14: warning: rule useless in parser due to conflicts: exp: 'a' [-Wother] Now bison reports: in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr] in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother] exp: 'a' | 'a'; ^^^ and "bison -fno-caret" reports: in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr] in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother] *** Enhancements of the -Werror option The -Werror=CATEGORY option is now recognized, and will treat specified warnings as errors. The warnings need not have been explicitly activated using the -W option, this is similar to what GCC 4.7 does. For example, given the following command line, Bison will treat both warnings related to POSIX Yacc incompatibilities and S/R conflicts as errors (and only those): $ bison -Werror=yacc,error=conflicts-sr input.y If no categories are specified, -Werror will make all active warnings into errors. For example, the following line does the same the previous example: $ bison -Werror -Wnone -Wyacc -Wconflicts-sr input.y (By default -Wconflicts-sr,conflicts-rr,deprecated,other is enabled.) Note that the categories in this -Werror option may not be prefixed with "no-". However, -Wno-error[=CATEGORY] is valid. Note that -y enables -Werror=yacc. Therefore it is now possible to require Yacc-like behavior (e.g., always generate y.tab.c), but to report incompatibilities as warnings: "-y -Wno-error=yacc". *** The display of warnings is now richer The option that controls a given warning is now displayed: foo.y:4.6: warning: type clash on default action: <foo> != <bar> [-Wother] In the case of warnings treated as errors, the prefix is changed from "warning: " to "error: ", and the suffix is displayed, in a manner similar to GCC, as [-Werror=CATEGORY]. For instance, where the previous version of Bison would report (and exit with failure): bison: warnings being treated as errors input.y:1.1: warning: stray ',' treated as white space it now reports: input.y:1.1: error: stray ',' treated as white space [-Werror=other] *** Deprecated constructs The new 'deprecated' warning category flags obsolete constructs whose support will be discontinued. It is enabled by default. These warnings used to be reported as 'other' warnings. *** Useless semantic types Bison now warns about useless (uninhabited) semantic types. Since semantic types are not declared to Bison (they are defined in the opaque %union structure), it is %printer/%destructor directives about useless types that trigger the warning: %token <type1> term %type <type2> nterm %printer {} <type1> <type3> %destructor {} <type2> <type4> %% nterm: term { $$ = $1; }; 3.28-34: warning: type <type3> is used, but is not associated to any symbol 4.28-34: warning: type <type4> is used, but is not associated to any symbol *** Undefined but unused symbols Bison used to raise an error for undefined symbols that are not used in the grammar. This is now only a warning. %printer {} symbol1 %destructor {} symbol2 %type <type> symbol3 %% exp: "a"; *** Useless destructors or printers Bison now warns about useless destructors or printers. In the following example, the printer for <type1>, and the destructor for <type2> are useless: all symbols of <type1> (token1) already have a printer, and all symbols of type <type2> (token2) already have a destructor. %token <type1> token1 <type2> token2 <type3> token3 <type4> token4 %printer {} token1 <type1> <type3> %destructor {} token2 <type2> <type4> *** Conflicts The warnings and error messages about shift/reduce and reduce/reduce conflicts have been normalized. For instance on the following foo.y file: %glr-parser %% exp: exp '+' exp | '0' | '0'; compare the previous version of bison: $ bison foo.y foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce $ bison -Werror foo.y bison: warnings being treated as errors foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce with the new behavior: $ bison foo.y foo.y: warning: 1 shift/reduce conflict [-Wconflicts-sr] foo.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr] $ bison -Werror foo.y foo.y: error: 1 shift/reduce conflict [-Werror=conflicts-sr] foo.y: error: 2 reduce/reduce conflicts [-Werror=conflicts-rr] When %expect or %expect-rr is used, such as with bar.y: %expect 0 %glr-parser %% exp: exp '+' exp | '0' | '0'; Former behavior: $ bison bar.y bar.y: conflicts: 1 shift/reduce, 2 reduce/reduce bar.y: expected 0 shift/reduce conflicts bar.y: expected 0 reduce/reduce conflicts New one: $ bison bar.y bar.y: error: shift/reduce conflicts: 1 found, 0 expected bar.y: error: reduce/reduce conflicts: 2 found, 0 expected ** Incompatibilities with POSIX Yacc The 'yacc' category is no longer part of '-Wall', enable it explicitly with '-Wyacc'. ** Additional yylex/yyparse arguments The new directive %param declares additional arguments to both yylex and yyparse. The %lex-param, %parse-param, and %param directives support one or more arguments. Instead of %lex-param {arg1_type *arg1} %lex-param {arg2_type *arg2} %parse-param {arg1_type *arg1} %parse-param {arg2_type *arg2} one may now declare %param {arg1_type *arg1} {arg2_type *arg2} ** Types of values for %define variables Bison used to make no difference between '%define foo bar' and '%define foo "bar"'. The former is now called a 'keyword value', and the latter a 'string value'. A third kind was added: 'code values', such as '%define foo {bar}'. Keyword variables are used for fixed value sets, e.g., %define lr.type lalr Code variables are used for value in the target language, e.g., %define api.value.type {struct semantic_type} String variables are used remaining cases, e.g. file names. ** Variable api.token.prefix The variable api.token.prefix changes the way tokens are identified in the generated files. This is especially useful to avoid collisions with identifiers in the target language. For instance %token FILE for ERROR %define api.token.prefix {TOK_} %% start: FILE for ERROR; will generate the definition of the symbols TOK_FILE, TOK_for, and TOK_ERROR in the generated sources. In particular, the scanner must use these prefixed token names, although the grammar itself still uses the short names (as in the sample rule given above). ** Variable api.value.type This new %define variable supersedes the #define macro YYSTYPE. The use of YYSTYPE is discouraged. In particular, #defining YYSTYPE *and* either using %union or %defining api.value.type results in undefined behavior. Either define api.value.type, or use "%union": %union { int ival; char *sval; } %token <ival> INT "integer" %token <sval> STRING "string" %printer { fprintf (yyo, "%d", $$); } <ival> %destructor { free ($$); } <sval> /* In yylex(). */ yylval.ival = 42; return INT; yylval.sval = "42"; return STRING; The %define variable api.value.type supports both keyword and code values. The keyword value 'union' means that the user provides genuine types, not union member names such as "ival" and "sval" above (WARNING: will fail if -y/--yacc/%yacc is enabled). %define api.value.type union %token <int> INT "integer" %token <char *> STRING "string" %printer { fprintf (yyo, "%d", $$); } <int> %destructor { free ($$); } <char *> /* In yylex(). */ yylval.INT = 42; return INT; yylval.STRING = "42"; return STRING; The keyword value variant is somewhat equivalent, but for C++ special provision is made to allow classes to be used (more about this below). %define api.value.type variant %token <int> INT "integer" %token <std::string> STRING "string" Code values (in braces) denote user defined types. This is where YYSTYPE used to be used. %code requires { struct my_value { enum { is_int, is_string } kind; union { int ival; char *sval; } u; }; } %define api.value.type {struct my_value} %token <u.ival> INT "integer" %token <u.sval> STRING "string" %printer { fprintf (yyo, "%d", $$); } <u.ival> %destructor { free ($$); } <u.sval> /* In yylex(). */ yylval.u.ival = 42; return INT; yylval.u.sval = "42"; return STRING; ** Variable parse.error This variable controls the verbosity of error messages. The use of the %error-verbose directive is deprecated in favor of "%define parse.error verbose". ** Renamed %define variables The following variables have been renamed for consistency. Backward compatibility is ensured, but upgrading is recommended. lr.default-reductions -> lr.default-reduction lr.keep-unreachable-states -> lr.keep-unreachable-state namespace -> api.namespace stype -> api.value.type ** Semantic predicates Contributed by Paul Hilfinger. The new, experimental, semantic-predicate feature allows actions of the form "%?{ BOOLEAN-EXPRESSION }", which cause syntax errors (as for YYERROR) if the expression evaluates to 0, and are evaluated immediately in GLR parsers, rather than being deferred. The result is that they allow the programmer to prune possible parses based on the values of run-time expressions. ** The directive %expect-rr is now an error in non GLR mode It used to be an error only if used in non GLR mode, _and_ if there are reduce/reduce conflicts. ** Tokens are numbered in their order of appearance Contributed by Valentin Tolmer. With '%token A B', A had a number less than the one of B. However, precedence declarations used to generate a reversed order. This is now fixed, and introducing tokens with any of %token, %left, %right, %precedence, or %nonassoc yields the same result. When mixing declarations of tokens with a litteral character (e.g., 'a') or with an identifier (e.g., B) in a precedence declaration, Bison numbered the litteral characters first. For example %right A B 'c' 'd' would lead to the tokens declared in this order: 'c' 'd' A B. Again, the input order is now preserved. These changes were made so that one can remove useless precedence and associativity declarations (i.e., map %nonassoc, %left or %right to %precedence, or to %token) and get exactly the same output. ** Useless precedence and associativity Contributed by Valentin Tolmer. When developing and maintaining a grammar, useless associativity and precedence directives are common. They can be a nuisance: new ambiguities arising are sometimes masked because their conflicts are resolved due to the extra precedence or associativity information. Furthermore, it can hinder the comprehension of a new grammar: one will wonder about the role of a precedence, where in fact it is useless. The following changes aim at detecting and reporting these extra directives. *** Precedence warning category A new category of warning, -Wprecedence, was introduced. It flags the useless precedence and associativity directives. *** Useless associativity Bison now warns about symbols with a declared associativity that is never used to resolve conflicts. In that case, using %precedence is sufficient; the parsing tables will remain unchanged. Solving these warnings may raise useless precedence warnings, as the symbols no longer have associativity. For example: %left '+' %left '*' %% exp: "number" | exp '+' "number" | exp '*' exp ; will produce a warning: useless associativity for '+', use %precedence [-Wprecedence] %left '+' ^^^ *** Useless precedence Bison now warns about symbols with a declared precedence and no declared associativity (i.e., declared with %precedence), and whose precedence is never used. In that case, the symbol can be safely declared with %token instead, without modifying the parsing tables. For example: %precedence '=' %% exp: "var" '=' "number"; will produce a warning: useless precedence for '=' [-Wprecedence] %precedence '=' ^^^ *** Useless precedence and associativity In case of both useless precedence and associativity, the issue is flagged as follows: %nonassoc '=' %% exp: "var" '=' "number"; The warning is: warning: useless precedence and associativity for '=' [-Wprecedence] %nonassoc '=' ^^^ ** Empty rules With help from Joel E. Denny and Gabriel Rassoul. Empty rules (i.e., with an empty right-hand side) can now be explicitly marked by the new %empty directive. Using %empty on a non-empty rule is an error. The new -Wempty-rule warning reports empty rules without %empty. On the following grammar: %% s: a b c; a: ; b: %empty; c: 'a' %empty; bison reports: 3.4-5: warning: empty rule without %empty [-Wempty-rule] a: {} ^^ 5.8-13: error: %empty on non-empty rule c: 'a' %empty {}; ^^^^^^ ** Java skeleton improvements The constants for token names were moved to the Lexer interface. Also, it is possible to add code to the parser's constructors using "%code init" and "%define init_throws". Contributed by Paolo Bonzini. The Java skeleton now supports push parsing. Contributed by Dennis Heimbigner. ** C++ skeletons improvements *** The parser header is no longer mandatory (lalr1.cc, glr.cc) Using %defines is now optional. Without it, the needed support classes are defined in the generated parser, instead of additional files (such as location.hh, position.hh and stack.hh). *** Locations are no longer mandatory (lalr1.cc, glr.cc) Both lalr1.cc and glr.cc no longer require %location. *** syntax_error exception (lalr1.cc) The C++ parser features a syntax_error exception, which can be thrown from the scanner or from user rules to raise syntax errors. This facilitates reporting errors caught in sub-functions (e.g., rejecting too large integral literals from a conversion function used by the scanner, or rejecting invalid combinations from a factory invoked by the user actions). *** %define api.value.type variant This is based on a submission from Michiel De Wilde. With help from Théophile Ranquet. In this mode, complex C++ objects can be used as semantic values. For instance: %token <::std::string> TEXT; %token <int> NUMBER; %token SEMICOLON ";" %type <::std::string> item; %type <::std::list<std::string>> list; %% result: list { std::cout << $1 << std::endl; } ; list: %empty { /* Generates an empty string list. */ } | list item ";" { std::swap ($$, $1); $$.push_back ($2); } ; item: TEXT { std::swap ($$, $1); } | NUMBER { $$ = string_cast ($1); } ; *** %define api.token.constructor When variants are enabled, Bison can generate functions to build the tokens. This guarantees that the token type (e.g., NUMBER) is consistent with the semantic value (e.g., int): parser::symbol_type yylex () { parser::location_type loc = ...; ... return parser::make_TEXT ("Hello, world!", loc); ... return parser::make_NUMBER (42, loc); ... return parser::make_SEMICOLON (loc); ... } *** C++ locations There are operator- and operator-= for 'location'. Negative line/column increments can no longer underflow the resulting value.

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