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Bison 3.8.1 released

From: Akim Demaille
Subject: Bison 3.8.1 released
Date: Sat, 11 Sep 2021 19:05:16 +0200


I'm very pleased to announce the release of Bison 3.8(.1), whose main
novelty is the D backend for deterministic parsers, contributed by
Adela Vais.  It supports all the bells and whistles of Bison's other
deterministic parsers, which include: pull/push interfaces, verbose
and custom error messages, lookahead correction, LALR(1), IELR(1),
canonical LR(1), token constructors, internationalization, locations,
printers, token and symbol prefixes, and more.

There are several other notable changes.  Please see the detailed NEWS
below for more details.



Here are the compressed sources:   (6.1MB)   (3.1MB)   (3.1MB)

Here are the GPG detached signatures[*]:

Use a mirror for higher download bandwidth:

Here are the SHA1 and SHA256 checksums:

79e97c868475c0e20286d62021f2a7cfd20610f7  bison-3.8.1.tar.gz
zjGKRxlhVft8JpErUTEC89DhR1fC5JXjRgh1e2EznFw  bison-3.8.1.tar.gz
e7fe4142c22ac5353ec4416652a56e9da951ffa5  bison-3.8.1.tar.lz
AJ2nWoBj4aO9IVRrN+UkISBWiR/CySr6EanzlphoIbg  bison-3.8.1.tar.lz
9772ea3130d6cbddaefe29a659698775a5701394  bison-3.8.1.tar.xz
MfxgJIiq1r3s8MzFVuD8cvxXzcWVz5I5jwIODPSYDxU  bison-3.8.1.tar.xz

The SHA256 checksum is base64 encoded, instead of the
hexadecimal encoding that most checksum tools default to.

[*] Use a .sig file to verify that the corresponding file (without the
.sig suffix) is intact.  First, be sure to download both the .sig file
and the corresponding tarball.  Then, run a command like this:

  gpg --verify bison-3.8.1.tar.gz.sig

If that command fails because you don't have the required public key,
then run this command to import it:

  gpg --keyserver --recv-keys 0DDCAA3278D5264E

and rerun the 'gpg --verify' command.

This release was bootstrapped with the following tools:
  Autoconf 2.71
  Automake 1.16b
  Flex 2.6.4
  Gnulib v0.1-4853-g964ce0a92


GNU Bison is a general-purpose parser generator that converts an annotated
context-free grammar into a deterministic LR or generalized LR (GLR) parser
employing LALR(1) parser tables.  Bison can also generate IELR(1) or
canonical LR(1) parser tables.  Once you are proficient with Bison, you can
use it to develop a wide range of language parsers, from those used in
simple desk calculators to complex programming languages.

Bison is upward compatible with Yacc: all properly-written Yacc grammars
work with Bison with no change.  Anyone familiar with Yacc should be able to
use Bison with little trouble.  You need to be fluent in C, C++, D or Java
programming in order to use Bison.

Bison and the parsers it generates are portable, they do not require any
specific compilers.

GNU Bison's home page is



* Noteworthy changes in release 3.8.1 (2021-09-11) [stable]

  The generation of prototypes for yylex and yyerror in Yacc mode is
  breaking existing grammar files.  To avoid breaking too many grammars, the
  prototypes are now generated when `-y/--yacc` is used *and* the
  `POSIXLY_CORRECT` environment variable is defined.

  Avoid using `-y`/`--yacc` simply to comply with Yacc's file name
  conventions, rather, use `-o`.  Autoconf's AC_PROG_YACC macro uses
  `-y`.  Avoid it if possible, for instance by using gnulib's gl_PROG_BISON.

* Noteworthy changes in release 3.8 (2021-09-07) [stable]

** Backward incompatible changes

  In conformance with the recommendations of the Graphviz team
  (, `-g`/`--graph`
  now generates a *.gv file by default, instead of *.dot.  A transition
  started in Bison 3.4.

  To comply with the latest POSIX standard, in Yacc compatibility mode
  (options `-y`/`--yacc`) Bison now generates prototypes for yyerror and
  yylex.  In some situations, this is breaking compatibility: if the user
  has already declared these functions but with some differences (e.g., to
  declare them as static, or to use specific attributes), the generated
  parser will fail to compile.  To disable these prototypes, #define yyerror
  (to `yyerror`), and likewise for yylex.

** Deprecated features

  Support for the YYPRINT macro is removed. It worked only with yacc.c and
  only for tokens.  It was obsoleted by %printer, introduced in Bison 1.50
  (November 2002).

  It has always been recommended to prefer `%define api.value.type foo` to
  `#define YYSTYPE foo`.  The latter is supported in C for compatibility
  with Yacc, but not in C++.  Warnings are now issued if `#define YYSTYPE`
  is used in C++, and eventually support will be removed.

  In C++ code, prefer value_type to semantic_type to denote the semantic
  value type, which is specified by the `api.value.type` %define variable.

** New features

*** A skeleton for the D programming language

  The "lalr1.d" skeleton is now officially part of Bison.

  It was originally contributed by Oliver Mangold, based on Paolo Bonzini's, and was improved by H. S. Teoh.  Adela Vais then took over
  maintenance and invested a lot of efforts to complete, test and document

  It now supports all the bells and whistles of the other deterministic
  parsers, which include: pull/push interfaces, verbose and custom error
  messages, lookahead correction, token constructors, internationalization,
  locations, printers, token and symbol prefixes, etc.

  Two examples demonstrate the D parsers: a basic one (examples/d/simple),
  and an advanced one (examples/d/calc).

*** Option -H, --header and directive %header

  The option `-H`/`--header` supersedes the option `--defines`, and the
  directive %header supersedes %defines.  Both `--defines` and `%defines`
  are, of course, maintained for backward compatibility.

*** Option --html

  Since version 2.4 Bison can be used to generate HTML reports.  However it
  was a two-step process: first bison must be invoked with option `--xml`,
  and then xsltproc must be run to the convert the XML reports into HTML.

  The new option `--html` combines these steps.  The xsltproc program must
  be available.

*** A C++ native GLR parser

  A new version of the C++ GLR parser was added: "".  It generates
  "true C++11", instead of a C++ wrapper around a C parser as does the
  existing "" parser.  As a first significant consequence, it supports
  `%define api.value.type variant`, contrary to

  It should be upward compatible in terms of interface, feature and
  performance to "". To try it out, simply use

  %skeleton ""

  It will eventually replace "".  However we need user feedback on
  this skeleton.  _Please_ report your results and comments about it.

*** Counterexamples

  Counterexamples now show the rule numbers, and always show ε for rules
  with an empty right-hand side.  For instance

    ↳ 1: e1       e2     "a"
         ↳ 3: ε • ↳ 1: ε

  instead of

    ↳ e1  e2  "a"
      ↳ • ↳ ε

*** Lookahead correction in Java

  The Java skeleton ( now supports LAC, via the `parse.lac`
  %define variable.

*** Abort parsing for memory exhaustion (C)

  User actions may now use `YYNOMEM` (similar to `YYACCEPT` and `YYABORT`)
  to abort the current parse with memory exhaustion.

*** Printing locations in debug traces (C)

  The `YYLOCATION_PRINT(File, Loc)` macro prints a location.  It is defined
  when (i) locations are enabled, (ii) the default type for locations is
  used, (iii) debug traces are enabled, and (iv) `YYLOCATION_PRINT` is not
  already defined.

  Users may define `YYLOCATION_PRINT` to cover other cases.

*** GLR traces

  There were no debug traces for deferred calls to user actions.  They are
  logged now.

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