\input texinfo @c -*-texinfo-*-
@comment %**start of header
@setfilename bison.info
-@settitle Bison 1.25
+@include version.texi
+@settitle Bison @value{VERSION}
@setchapternewpage odd
@iftex
@finalout
@end iftex
-@c SMALL BOOK version
+@c SMALL BOOK version
@c This edition has been formatted so that you can format and print it in
-@c the smallbook format.
+@c the smallbook format.
@c @smallbook
-@c next time, consider using @set for edition number, etc...
-
@c Set following if you have the new `shorttitlepage' command
@c @clear shorttitlepage-enabled
@c @set shorttitlepage-enabled
@end ifinfo
@comment %**end of header
+@ifinfo
+@format
+START-INFO-DIR-ENTRY
+* bison: (bison). GNU Project parser generator (yacc replacement).
+END-INFO-DIR-ENTRY
+@end format
+@end ifinfo
+
@ifinfo
This file documents the Bison parser generator.
-Copyright (C) 1988, 89, 90, 91, 92, 93, 1995 Free Software Foundation, Inc.
+Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998, 1999,
+2000, 2001
+Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
@titlepage
@title Bison
@subtitle The YACC-compatible Parser Generator
-@subtitle November 1995, Bison Version 1.25
+@subtitle @value{UPDATED}, Bison Version @value{VERSION}
@author by Charles Donnelly and Richard Stallman
@page
@vskip 0pt plus 1filll
-Copyright @copyright{} 1988, 89, 90, 91, 92, 93, 1995 Free Software
-Foundation
+Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998,
+1999, 2000, 2001
+Free Software Foundation, Inc.
@sp 2
Published by the Free Software Foundation @*
59 Temple Place, Suite 330 @*
Boston, MA 02111-1307 USA @*
-Printed copies are available for $15 each.@*
-ISBN 1-882114-45-0
+Printed copies are available from the Free Software Foundation.@*
+ISBN 1-882114-44-2
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
@sp 2
Cover art by Etienne Suvasa.
@end titlepage
-@page
+
+@contents
@node Top, Introduction, (dir), (dir)
@ifinfo
-This manual documents version 1.25 of Bison.
+This manual documents version @value{VERSION} of Bison.
@end ifinfo
@menu
-* Introduction::
-* Conditions::
+* Introduction::
+* Conditions::
* Copying:: The GNU General Public License says
how you can copy and share Bison
* Invocation:: How to run Bison (to produce the parser source file).
* Table of Symbols:: All the keywords of the Bison language are explained.
* Glossary:: Basic concepts are explained.
+* Copying This Manual:: License for copying this manual.
* Index:: Cross-references to the text.
--- The Detailed Node Listing ---
Reverse Polish Notation Calculator
-* Decls: Rpcalc Decls. Bison and C declarations for rpcalc.
+* Decls: Rpcalc Decls. Prologue (declarations) for rpcalc.
* Rules: Rpcalc Rules. Grammar Rules for rpcalc, with explanation.
* Lexer: Rpcalc Lexer. The lexical analyzer.
* Main: Rpcalc Main. The controlling function.
Grammar Rules for @code{rpcalc}
-* Rpcalc Input::
-* Rpcalc Line::
-* Rpcalc Expr::
+* Rpcalc Input::
+* Rpcalc Line::
+* Rpcalc Expr::
Multi-Function Calculator: @code{mfcalc}
Outline of a Bison Grammar
-* C Declarations:: Syntax and usage of the C declarations section.
+* Prologue:: Syntax and usage of the prologue (declarations section).
* Bison Declarations:: Syntax and usage of the Bison declarations section.
* Grammar Rules:: Syntax and usage of the grammar rules section.
-* C Code:: Syntax and usage of the additional C code section.
+* Epilogue:: Syntax and usage of the epilogue (additional code section).
Defining Language Semantics
Parser C-Language Interface
* Parser Function:: How to call @code{yyparse} and what it returns.
-* Lexical:: You must supply a function @code{yylex}
+* Lexical:: You must supply a function @code{yylex}
which reads tokens.
* Error Reporting:: You must supply a function @code{yyerror}.
* Action Features:: Special features for use in actions.
* Pure Calling:: How the calling convention differs
in a pure parser (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}).
-The Bison Parser Algorithm
+The Bison Parser Algorithm
* Look-Ahead:: Parser looks one token ahead when deciding what to do.
* Shift/Reduce:: Conflicts: when either shifting or reduction is valid.
Invoking Bison
-* Bison Options:: All the options described in detail,
+* Bison Options:: All the options described in detail,
in alphabetical order by short options.
* Option Cross Key:: Alphabetical list of long options.
* VMS Invocation:: Bison command syntax on VMS.
+
+Copying This Manual
+
+* GNU Free Documentation License:: License for copying this manual.
+
@end menu
@node Introduction, Conditions, Top, Top
Bison was written primarily by Robert Corbett; Richard Stallman made it
Yacc-compatible. Wilfred Hansen of Carnegie Mellon University added
-multicharacter string literals and other features.
+multi-character string literals and other features.
-This edition corresponds to version 1.25 of Bison.
+This edition corresponds to version @value{VERSION} of Bison.
@node Conditions, Copying, Introduction, Top
@unnumbered Conditions for Using Bison
As of Bison version 1.24, we have changed the distribution terms for
-@code{yyparse} to permit using Bison's output in non-free programs.
+@code{yyparse} to permit using Bison's output in nonfree programs.
Formerly, Bison parsers could be used only in programs that were free
software.
The other GNU programming tools, such as the GNU C compiler, have never
-had such a requirement. They could always be used for non-free
+had such a requirement. They could always be used for nonfree
software. The reason Bison was different was not due to a special
policy decision; it resulted from applying the usual General Public
License to all of the Bison source code.
practical conditions for using Bison match the practical conditions for
using the other GNU tools.
-@node Copying, Concepts, Conditions, Top
-@unnumbered GNU GENERAL PUBLIC LICENSE
-@center Version 2, June 1991
-
-@display
-Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc.
-675 Mass Ave, Cambridge, MA 02139, USA
-
-Everyone is permitted to copy and distribute verbatim copies
-of this license document, but changing it is not allowed.
-@end display
-
-@unnumberedsec Preamble
-
- The licenses for most software are designed to take away your
-freedom to share and change it. By contrast, the GNU General Public
-License is intended to guarantee your freedom to share and change free
-software---to make sure the software is free for all its users. This
-General Public License applies to most of the Free Software
-Foundation's software and to any other program whose authors commit to
-using it. (Some other Free Software Foundation software is covered by
-the GNU Library General Public License instead.) You can apply it to
-your programs, too.
-
- When we speak of free software, we are referring to freedom, not
-price. Our General Public Licenses are designed to make sure that you
-have the freedom to distribute copies of free software (and charge for
-this service if you wish), that you receive source code or can get it
-if you want it, that you can change the software or use pieces of it
-in new free programs; and that you know you can do these things.
-
- To protect your rights, we need to make restrictions that forbid
-anyone to deny you these rights or to ask you to surrender the rights.
-These restrictions translate to certain responsibilities for you if you
-distribute copies of the software, or if you modify it.
-
- For example, if you distribute copies of such a program, whether
-gratis or for a fee, you must give the recipients all the rights that
-you have. You must make sure that they, too, receive or can get the
-source code. And you must show them these terms so they know their
-rights.
-
- We protect your rights with two steps: (1) copyright the software, and
-(2) offer you this license which gives you legal permission to copy,
-distribute and/or modify the software.
-
- Also, for each author's protection and ours, we want to make certain
-that everyone understands that there is no warranty for this free
-software. If the software is modified by someone else and passed on, we
-want its recipients to know that what they have is not the original, so
-that any problems introduced by others will not reflect on the original
-authors' reputations.
-
- Finally, any free program is threatened constantly by software
-patents. We wish to avoid the danger that redistributors of a free
-program will individually obtain patent licenses, in effect making the
-program proprietary. To prevent this, we have made it clear that any
-patent must be licensed for everyone's free use or not licensed at all.
-
- The precise terms and conditions for copying, distribution and
-modification follow.
-
-@iftex
-@unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
-@end iftex
-@ifinfo
-@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
-@end ifinfo
-
-@enumerate 0
-@item
-This License applies to any program or other work which contains
-a notice placed by the copyright holder saying it may be distributed
-under the terms of this General Public License. The ``Program'', below,
-refers to any such program or work, and a ``work based on the Program''
-means either the Program or any derivative work under copyright law:
-that is to say, a work containing the Program or a portion of it,
-either verbatim or with modifications and/or translated into another
-language. (Hereinafter, translation is included without limitation in
-the term ``modification''.) Each licensee is addressed as ``you''.
-
-Activities other than copying, distribution and modification are not
-covered by this License; they are outside its scope. The act of
-running the Program is not restricted, and the output from the Program
-is covered only if its contents constitute a work based on the
-Program (independent of having been made by running the Program).
-Whether that is true depends on what the Program does.
-
-@item
-You may copy and distribute verbatim copies of the Program's
-source code as you receive it, in any medium, provided that you
-conspicuously and appropriately publish on each copy an appropriate
-copyright notice and disclaimer of warranty; keep intact all the
-notices that refer to this License and to the absence of any warranty;
-and give any other recipients of the Program a copy of this License
-along with the Program.
-
-You may charge a fee for the physical act of transferring a copy, and
-you may at your option offer warranty protection in exchange for a fee.
-
-@item
-You may modify your copy or copies of the Program or any portion
-of it, thus forming a work based on the Program, and copy and
-distribute such modifications or work under the terms of Section 1
-above, provided that you also meet all of these conditions:
-
-@enumerate a
-@item
-You must cause the modified files to carry prominent notices
-stating that you changed the files and the date of any change.
-
-@item
-You must cause any work that you distribute or publish, that in
-whole or in part contains or is derived from the Program or any
-part thereof, to be licensed as a whole at no charge to all third
-parties under the terms of this License.
-
-@item
-If the modified program normally reads commands interactively
-when run, you must cause it, when started running for such
-interactive use in the most ordinary way, to print or display an
-announcement including an appropriate copyright notice and a
-notice that there is no warranty (or else, saying that you provide
-a warranty) and that users may redistribute the program under
-these conditions, and telling the user how to view a copy of this
-License. (Exception: if the Program itself is interactive but
-does not normally print such an announcement, your work based on
-the Program is not required to print an announcement.)
-@end enumerate
-
-These requirements apply to the modified work as a whole. If
-identifiable sections of that work are not derived from the Program,
-and can be reasonably considered independent and separate works in
-themselves, then this License, and its terms, do not apply to those
-sections when you distribute them as separate works. But when you
-distribute the same sections as part of a whole which is a work based
-on the Program, the distribution of the whole must be on the terms of
-this License, whose permissions for other licensees extend to the
-entire whole, and thus to each and every part regardless of who wrote it.
-
-Thus, it is not the intent of this section to claim rights or contest
-your rights to work written entirely by you; rather, the intent is to
-exercise the right to control the distribution of derivative or
-collective works based on the Program.
-
-In addition, mere aggregation of another work not based on the Program
-with the Program (or with a work based on the Program) on a volume of
-a storage or distribution medium does not bring the other work under
-the scope of this License.
-
-@item
-You may copy and distribute the Program (or a work based on it,
-under Section 2) in object code or executable form under the terms of
-Sections 1 and 2 above provided that you also do one of the following:
-
-@enumerate a
-@item
-Accompany it with the complete corresponding machine-readable
-source code, which must be distributed under the terms of Sections
-1 and 2 above on a medium customarily used for software interchange; or,
-
-@item
-Accompany it with a written offer, valid for at least three
-years, to give any third party, for a charge no more than your
-cost of physically performing source distribution, a complete
-machine-readable copy of the corresponding source code, to be
-distributed under the terms of Sections 1 and 2 above on a medium
-customarily used for software interchange; or,
-
-@item
-Accompany it with the information you received as to the offer
-to distribute corresponding source code. (This alternative is
-allowed only for noncommercial distribution and only if you
-received the program in object code or executable form with such
-an offer, in accord with Subsection b above.)
-@end enumerate
-
-The source code for a work means the preferred form of the work for
-making modifications to it. For an executable work, complete source
-code means all the source code for all modules it contains, plus any
-associated interface definition files, plus the scripts used to
-control compilation and installation of the executable. However, as a
-special exception, the source code distributed need not include
-anything that is normally distributed (in either source or binary
-form) with the major components (compiler, kernel, and so on) of the
-operating system on which the executable runs, unless that component
-itself accompanies the executable.
-
-If distribution of executable or object code is made by offering
-access to copy from a designated place, then offering equivalent
-access to copy the source code from the same place counts as
-distribution of the source code, even though third parties are not
-compelled to copy the source along with the object code.
-
-@item
-You may not copy, modify, sublicense, or distribute the Program
-except as expressly provided under this License. Any attempt
-otherwise to copy, modify, sublicense or distribute the Program is
-void, and will automatically terminate your rights under this License.
-However, parties who have received copies, or rights, from you under
-this License will not have their licenses terminated so long as such
-parties remain in full compliance.
-
-@item
-You are not required to accept this License, since you have not
-signed it. However, nothing else grants you permission to modify or
-distribute the Program or its derivative works. These actions are
-prohibited by law if you do not accept this License. Therefore, by
-modifying or distributing the Program (or any work based on the
-Program), you indicate your acceptance of this License to do so, and
-all its terms and conditions for copying, distributing or modifying
-the Program or works based on it.
-
-@item
-Each time you redistribute the Program (or any work based on the
-Program), the recipient automatically receives a license from the
-original licensor to copy, distribute or modify the Program subject to
-these terms and conditions. You may not impose any further
-restrictions on the recipients' exercise of the rights granted herein.
-You are not responsible for enforcing compliance by third parties to
-this License.
-
-@item
-If, as a consequence of a court judgment or allegation of patent
-infringement or for any other reason (not limited to patent issues),
-conditions are imposed on you (whether by court order, agreement or
-otherwise) that contradict the conditions of this License, they do not
-excuse you from the conditions of this License. If you cannot
-distribute so as to satisfy simultaneously your obligations under this
-License and any other pertinent obligations, then as a consequence you
-may not distribute the Program at all. For example, if a patent
-license would not permit royalty-free redistribution of the Program by
-all those who receive copies directly or indirectly through you, then
-the only way you could satisfy both it and this License would be to
-refrain entirely from distribution of the Program.
-
-If any portion of this section is held invalid or unenforceable under
-any particular circumstance, the balance of the section is intended to
-apply and the section as a whole is intended to apply in other
-circumstances.
-
-It is not the purpose of this section to induce you to infringe any
-patents or other property right claims or to contest validity of any
-such claims; this section has the sole purpose of protecting the
-integrity of the free software distribution system, which is
-implemented by public license practices. Many people have made
-generous contributions to the wide range of software distributed
-through that system in reliance on consistent application of that
-system; it is up to the author/donor to decide if he or she is willing
-to distribute software through any other system and a licensee cannot
-impose that choice.
-
-This section is intended to make thoroughly clear what is believed to
-be a consequence of the rest of this License.
-
-@item
-If the distribution and/or use of the Program is restricted in
-certain countries either by patents or by copyrighted interfaces, the
-original copyright holder who places the Program under this License
-may add an explicit geographical distribution limitation excluding
-those countries, so that distribution is permitted only in or among
-countries not thus excluded. In such case, this License incorporates
-the limitation as if written in the body of this License.
-
-@item
-The Free Software Foundation may publish revised and/or new versions
-of the General Public License from time to time. Such new versions will
-be similar in spirit to the present version, but may differ in detail to
-address new problems or concerns.
-
-Each version is given a distinguishing version number. If the Program
-specifies a version number of this License which applies to it and ``any
-later version'', you have the option of following the terms and conditions
-either of that version or of any later version published by the Free
-Software Foundation. If the Program does not specify a version number of
-this License, you may choose any version ever published by the Free Software
-Foundation.
-
-@item
-If you wish to incorporate parts of the Program into other free
-programs whose distribution conditions are different, write to the author
-to ask for permission. For software which is copyrighted by the Free
-Software Foundation, write to the Free Software Foundation; we sometimes
-make exceptions for this. Our decision will be guided by the two goals
-of preserving the free status of all derivatives of our free software and
-of promoting the sharing and reuse of software generally.
-
-@iftex
-@heading NO WARRANTY
-@end iftex
-@ifinfo
-@center NO WARRANTY
-@end ifinfo
-
-@item
-BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
-FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
-OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
-PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
-OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS
-TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE
-PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
-REPAIR OR CORRECTION.
-
-@item
-IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
-WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
-REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
-INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
-OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
-TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
-YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
-PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
-POSSIBILITY OF SUCH DAMAGES.
-@end enumerate
-
-@iftex
-@heading END OF TERMS AND CONDITIONS
-@end iftex
-@ifinfo
-@center END OF TERMS AND CONDITIONS
-@end ifinfo
-
-@page
-@unnumberedsec How to Apply These Terms to Your New Programs
-
- If you develop a new program, and you want it to be of the greatest
-possible use to the public, the best way to achieve this is to make it
-free software which everyone can redistribute and change under these terms.
-
- To do so, attach the following notices to the program. It is safest
-to attach them to the start of each source file to most effectively
-convey the exclusion of warranty; and each file should have at least
-the ``copyright'' line and a pointer to where the full notice is found.
-
-@smallexample
-@var{one line to give the program's name and a brief idea of what it does.}
-Copyright (C) 19@var{yy} @var{name of author}
-
-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
-the Free Software Foundation; either version 2 of the License, or
-(at your option) any later version.
-
-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
-along with this program; if not, write to the Free Software
-Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
-@end smallexample
-
-Also add information on how to contact you by electronic and paper mail.
-
-If the program is interactive, make it output a short notice like this
-when it starts in an interactive mode:
-
-@smallexample
-Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author}
-Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
-type `show w'.
-This is free software, and you are welcome to redistribute it
-under certain conditions; type `show c' for details.
-@end smallexample
-
-The hypothetical commands @samp{show w} and @samp{show c} should show
-the appropriate parts of the General Public License. Of course, the
-commands you use may be called something other than @samp{show w} and
-@samp{show c}; they could even be mouse-clicks or menu items---whatever
-suits your program.
-
-You should also get your employer (if you work as a programmer) or your
-school, if any, to sign a ``copyright disclaimer'' for the program, if
-necessary. Here is a sample; alter the names:
-
-@smallexample
-Yoyodyne, Inc., hereby disclaims all copyright interest in the program
-`Gnomovision' (which makes passes at compilers) written by James Hacker.
-
-@var{signature of Ty Coon}, 1 April 1989
-Ty Coon, President of Vice
-@end smallexample
-
-This General Public License does not permit incorporating your program into
-proprietary programs. If your program is a subroutine library, you may
-consider it more useful to permit linking proprietary applications with the
-library. If this is what you want to do, use the GNU Library General
-Public License instead of this License.
+@include gpl.texi
@node Concepts, Examples, Copying, Top
@chapter The Concepts of Bison
a semantic value (the value of an integer,
the name of an identifier, etc.).
* Semantic Actions:: Each rule can have an action containing C code.
+* Locations Overview:: Tracking Locations.
* Bison Parser:: What are Bison's input and output,
how is the output used?
* Stages:: Stages in writing and running Bison grammars.
language, an expression typically has a semantic value that is a tree
structure describing the meaning of the expression.
-@node Semantic Actions, Bison Parser, Semantic Values, Concepts
+@node Semantic Actions, Locations Overview, Semantic Values, Concepts
@section Semantic Actions
@cindex semantic actions
@cindex actions, semantic
rule can have an @dfn{action} made up of C statements. Each time the
parser recognizes a match for that rule, the action is executed.
@xref{Actions}.
-
+
Most of the time, the purpose of an action is to compute the semantic value
of the whole construct from the semantic values of its parts. For example,
suppose we have a rule which says an expression can be the sum of two
The action says how to produce the semantic value of the sum expression
from the values of the two subexpressions.
-@node Bison Parser, Stages, Semantic Actions, Concepts
+@node Locations Overview, Bison Parser, Semantic Actions, Concepts
+@section Locations
+@cindex location
+@cindex textual position
+@cindex position, textual
+
+Many applications, like interpreters or compilers, have to produce verbose
+and useful error messages. To achieve this, one must be able to keep track of
+the @dfn{textual position}, or @dfn{location}, of each syntactic construct.
+Bison provides a mechanism for handling these locations.
+
+Each token has a semantic value. In a similar fashion, each token has an
+associated location, but the type of locations is the same for all tokens and
+groupings. Moreover, the output parser is equipped with a default data
+structure for storing locations (@pxref{Locations}, for more details).
+
+Like semantic values, locations can be reached in actions using a dedicated
+set of constructs. In the example above, the location of the whole grouping
+is @code{@@$}, while the locations of the subexpressions are @code{@@1} and
+@code{@@3}.
+
+When a rule is matched, a default action is used to compute the semantic value
+of its left hand side (@pxref{Actions}). In the same way, another default
+action is used for locations. However, the action for locations is general
+enough for most cases, meaning there is usually no need to describe for each
+rule how @code{@@$} should be formed. When building a new location for a given
+grouping, the default behavior of the output parser is to take the beginning
+of the first symbol, and the end of the last symbol.
+
+@node Bison Parser, Stages, Locations Overview, Concepts
@section Bison Output: the Parser File
@cindex Bison parser
@cindex Bison utility
@example
%@{
-@var{C declarations}
+@var{Prologue (declarations)}
%@}
@var{Bison declarations}
%%
@var{Grammar rules}
%%
-@var{Additional C code}
+@var{Epilogue (additional code)}
@end example
@noindent
The @samp{%%}, @samp{%@{} and @samp{%@}} are punctuation that appears
in every Bison grammar file to separate the sections.
-The C declarations may define types and variables used in the actions.
-You can also use preprocessor commands to define macros used there, and use
+The prologue may define types and variables used in the actions. You can
+also use preprocessor commands to define macros used there, and use
@code{#include} to include header files that do any of these things.
The Bison declarations declare the names of the terminal and nonterminal
The grammar rules define how to construct each nonterminal symbol from its
parts.
-The additional C code can contain any C code you want to use. Often the
-definition of the lexical analyzer @code{yylex} goes here, plus subroutines
-called by the actions in the grammar rules. In a simple program, all the
-rest of the program can go here.
+The epilogue can contain any code you want to use. Often the definition of
+the lexical analyzer @code{yylex} goes here, plus subroutines called by the
+actions in the grammar rules. In a simple program, all the rest of the
+program can go here.
@node Examples, Grammar File, Concepts, Top
@chapter Examples
@samp{.y} extension is a convention used for Bison input files.
@menu
-* Decls: Rpcalc Decls. Bison and C declarations for rpcalc.
+* Decls: Rpcalc Decls. Prologue (declarations) for rpcalc.
* Rules: Rpcalc Rules. Grammar Rules for rpcalc, with explanation.
* Lexer: Rpcalc Lexer. The lexical analyzer.
* Main: Rpcalc Main. The controlling function.
%% /* Grammar rules and actions follow */
@end example
-The C declarations section (@pxref{C Declarations, ,The C Declarations Section}) contains two
+The declarations section (@pxref{Prologue, , The prologue}) contains two
preprocessor directives.
The @code{#define} directive defines the macro @code{YYSTYPE}, thus
rule are referred to as @code{$1}, @code{$2}, and so on.
@menu
-* Rpcalc Input::
-* Rpcalc Line::
-* Rpcalc Expr::
+* Rpcalc Input::
+* Rpcalc Line::
+* Rpcalc Expr::
@end menu
@node Rpcalc Input, Rpcalc Line, , Rpcalc Rules
@example
@group
-/* Lexical analyzer returns a double floating point
+/* Lexical analyzer returns a double floating point
number on the stack and the token NUM, or the ASCII
character read if not a number. Skips all blanks
and tabs, returns 0 for EOF. */
@end group
@group
-yylex ()
+int
+yylex (void)
@{
int c;
/* skip white space */
- while ((c = getchar ()) == ' ' || c == '\t')
+ while ((c = getchar ()) == ' ' || c == '\t')
;
@end group
@group
/* process numbers */
- if (c == '.' || isdigit (c))
+ if (c == '.' || isdigit (c))
@{
ungetc (c, stdin);
scanf ("%lf", &yylval);
@end group
@group
/* return end-of-file */
- if (c == EOF)
+ if (c == EOF)
return 0;
/* return single chars */
- return c;
+ return c;
@}
@end group
@end example
@example
@group
-main ()
+int
+main (void)
@{
- yyparse ();
+ return yyparse ();
@}
@end group
@end example
@cindex error reporting routine
When @code{yyparse} detects a syntax error, it calls the error reporting
-function @code{yyerror} to print an error message (usually but not always
-@code{"parse error"}). It is up to the programmer to supply @code{yyerror}
-(@pxref{Interface, ,Parser C-Language Interface}), so here is the definition we will use:
+function @code{yyerror} to print an error message (usually but not
+always @code{"parse error"}). It is up to the programmer to supply
+@code{yyerror} (@pxref{Interface, ,Parser C-Language Interface}), so
+here is the definition we will use:
@example
@group
#include <stdio.h>
-yyerror (s) /* Called by yyparse on error */
- char *s;
+void
+yyerror (const char *s) /* Called by yyparse on error */
@{
printf ("%s\n", s);
@}
(@pxref{Error Recovery}). Otherwise, @code{yyparse} returns nonzero. We
have not written any error rules in this example, so any invalid input will
cause the calculator program to exit. This is not clean behavior for a
-real calculator, but it is adequate in the first example.
+real calculator, but it is adequate for the first example.
@node Rpcalc Gen, Rpcalc Compile, Rpcalc Error, RPN Calc
@subsection Running Bison to Make the Parser
@cindex running Bison (introduction)
-Before running Bison to produce a parser, we need to decide how to arrange
-all the source code in one or more source files. For such a simple example,
-the easiest thing is to put everything in one file. The definitions of
-@code{yylex}, @code{yyerror} and @code{main} go at the end, in the
-``additional C code'' section of the file (@pxref{Grammar Layout, ,The Overall Layout of a Bison Grammar}).
+Before running Bison to produce a parser, we need to decide how to
+arrange all the source code in one or more source files. For such a
+simple example, the easiest thing is to put everything in one file. The
+definitions of @code{yylex}, @code{yyerror} and @code{main} go at the
+end, in the epilogue of the file
+(@pxref{Grammar Layout, ,The Overall Layout of a Bison Grammar}).
For a large project, you would probably have several source files, and use
@code{make} to arrange to recompile them.
@end example
@noindent
-The functions @code{yylex}, @code{yyerror} and @code{main} can be the same
-as before.
+The functions @code{yylex}, @code{yyerror} and @code{main} can be the
+same as before.
There are two important new features shown in this code.
Up to this point, this manual has not addressed the issue of @dfn{error
recovery}---how to continue parsing after the parser detects a syntax
-error. All we have handled is error reporting with @code{yyerror}. Recall
-that by default @code{yyparse} returns after calling @code{yyerror}. This
-means that an erroneous input line causes the calculator program to exit.
-Now we show how to rectify this deficiency.
+error. All we have handled is error reporting with @code{yyerror}.
+Recall that by default @code{yyparse} returns after calling
+@code{yyerror}. This means that an erroneous input line causes the
+calculator program to exit. Now we show how to rectify this deficiency.
The Bison language itself includes the reserved word @code{error}, which
may be included in the grammar rules. In the example below it has
@end group
@end example
-This addition to the grammar allows for simple error recovery in the event
-of a parse error. If an expression that cannot be evaluated is read, the
-error will be recognized by the third rule for @code{line}, and parsing
-will continue. (The @code{yyerror} function is still called upon to print
-its message as well.) The action executes the statement @code{yyerrok}, a
-macro defined automatically by Bison; its meaning is that error recovery is
-complete (@pxref{Error Recovery}). Note the difference between
-@code{yyerrok} and @code{yyerror}; neither one is a misprint.@refill
+This addition to the grammar allows for simple error recovery in the
+event of a parse error. If an expression that cannot be evaluated is
+read, the error will be recognized by the third rule for @code{line},
+and parsing will continue. (The @code{yyerror} function is still called
+upon to print its message as well.) The action executes the statement
+@code{yyerrok}, a macro defined automatically by Bison; its meaning is
+that error recovery is complete (@pxref{Error Recovery}). Note the
+difference between @code{yyerrok} and @code{yyerror}; neither one is a
+misprint.@refill
This form of error recovery deals with syntax errors. There are other
kinds of errors; for example, division by zero, which raises an exception
It is easy to add new operators to the infix calculator as long as they are
only single-character literals. The lexical analyzer @code{yylex} passes
-back all non-number characters as tokens, so new grammar rules suffice for
+back all nonnumber characters as tokens, so new grammar rules suffice for
adding a new operator. But we want something more flexible: built-in
functions whose syntax has this form:
@smallexample
@group
+/* Fonctions type. */
+typedef double (*func_t) (double);
+
/* Data type for links in the chain of symbols. */
struct symrec
@{
char *name; /* name of symbol */
int type; /* type of symbol: either VAR or FNCT */
- union @{
- double var; /* value of a VAR */
- double (*fnctptr)(); /* value of a FNCT */
+ union
+ @{
+ double var; /* value of a VAR */
+ func_t fnctptr; /* value of a FNCT */
@} value;
struct symrec *next; /* link field */
@};
/* The symbol table: a chain of `struct symrec'. */
extern symrec *sym_table;
-symrec *putsym ();
-symrec *getsym ();
+symrec *putsym (const char *, func_t);
+symrec *getsym (const char *);
@end group
@end smallexample
@group
#include <stdio.h>
-main ()
+int
+main (void)
@{
init_table ();
- yyparse ();
+ return yyparse ();
@}
@end group
@group
-yyerror (s) /* Called by yyparse on error */
- char *s;
+void
+yyerror (const char *s) /* Called by yyparse on error */
@{
printf ("%s\n", s);
@}
struct init
@{
char *fname;
- double (*fnct)();
+ double (*fnct)(double);
@};
@end group
@group
-struct init arith_fncts[]
- = @{
- "sin", sin,
- "cos", cos,
- "atan", atan,
- "ln", log,
- "exp", exp,
- "sqrt", sqrt,
- 0, 0
- @};
+struct init arith_fncts[] =
+@{
+ "sin", sin,
+ "cos", cos,
+ "atan", atan,
+ "ln", log,
+ "exp", exp,
+ "sqrt", sqrt,
+ 0, 0
+@};
/* The symbol table: a chain of `struct symrec'. */
-symrec *sym_table = (symrec *)0;
+symrec *sym_table = (symrec *) 0;
@end group
@group
-init_table () /* puts arithmetic functions in table. */
+/* Put arithmetic functions in table. */
+void
+init_table (void)
@{
int i;
symrec *ptr;
@smallexample
symrec *
-putsym (sym_name,sym_type)
- char *sym_name;
- int sym_type;
+putsym (char *sym_name, int sym_type)
@{
symrec *ptr;
ptr = (symrec *) malloc (sizeof (symrec));
@}
symrec *
-getsym (sym_name)
- char *sym_name;
+getsym (const char *sym_name)
@{
symrec *ptr;
for (ptr = sym_table; ptr != (symrec *) 0;
The function @code{yylex} must now recognize variables, numeric values, and
the single-character arithmetic operators. Strings of alphanumeric
-characters with a leading nondigit are recognized as either variables or
+characters with a leading non-digit are recognized as either variables or
functions depending on what the symbol table says about them.
The string is passed to @code{getsym} for look up in the symbol table. If
@smallexample
@group
#include <ctype.h>
-yylex ()
+
+int
+yylex (void)
@{
int c;
C-language function that recognizes correct instances of the grammar.
The Bison grammar input file conventionally has a name ending in @samp{.y}.
+@xref{Invocation, ,Invoking Bison}.
@menu
* Grammar Outline:: Overall layout of the grammar file.
* Rules:: How to write grammar rules.
* Recursion:: Writing recursive rules.
* Semantics:: Semantic values and actions.
+* Locations:: Locations and actions.
* Declarations:: All kinds of Bison declarations are described here.
* Multiple Parsers:: Putting more than one Bison parser in one program.
@end menu
@example
%@{
-@var{C declarations}
+@var{Prologue}
%@}
@var{Bison declarations}
@var{Grammar rules}
%%
-@var{Additional C code}
+@var{Epilogue}
@end example
Comments enclosed in @samp{/* @dots{} */} may appear in any of the sections.
@menu
-* C Declarations:: Syntax and usage of the C declarations section.
+* Prologue:: Syntax and usage of the prologue.
* Bison Declarations:: Syntax and usage of the Bison declarations section.
* Grammar Rules:: Syntax and usage of the grammar rules section.
-* C Code:: Syntax and usage of the additional C code section.
+* Epilogue:: Syntax and usage of the epilogue.
@end menu
-@node C Declarations, Bison Declarations, , Grammar Outline
-@subsection The C Declarations Section
-@cindex C declarations section
-@cindex declarations, C
+@node Prologue, Bison Declarations, , Grammar Outline
+@subsection The prologue
+@cindex declarations section
+@cindex Prologue
+@cindex declarations
-The @var{C declarations} section contains macro definitions and
+The @var{prologue} section contains macro definitions and
declarations of functions and variables that are used in the actions in the
grammar rules. These are copied to the beginning of the parser file so
that they precede the definition of @code{yyparse}. You can use
need any C declarations, you may omit the @samp{%@{} and @samp{%@}}
delimiters that bracket this section.
-@node Bison Declarations, Grammar Rules, C Declarations, Grammar Outline
+@node Bison Declarations, Grammar Rules, Prologue, Grammar Outline
@subsection The Bison Declarations Section
@cindex Bison declarations (introduction)
@cindex declarations, Bison (introduction)
In some simple grammars you may not need any declarations.
@xref{Declarations, ,Bison Declarations}.
-@node Grammar Rules, C Code, Bison Declarations, Grammar Outline
+@node Grammar Rules, Epilogue, Bison Declarations, Grammar Outline
@subsection The Grammar Rules Section
@cindex grammar rules section
@cindex rules section for grammar
@samp{%%} (which precedes the grammar rules) may never be omitted even
if it is the first thing in the file.
-@node C Code, , Grammar Rules, Grammar Outline
-@subsection The Additional C Code Section
+@node Epilogue, , Grammar Rules, Grammar Outline
+@subsection The epilogue
@cindex additional C code section
+@cindex epilogue
@cindex C code, section for additional
-The @var{additional C code} section is copied verbatim to the end of
-the parser file, just as the @var{C declarations} section is copied to
-the beginning. This is the most convenient place to put anything
-that you want to have in the parser file but which need not come before
-the definition of @code{yyparse}. For example, the definitions of
-@code{yylex} and @code{yyerror} often go here. @xref{Interface, ,Parser C-Language Interface}.
+The @var{epilogue} is copied verbatim to the end of the parser file, just as
+the @var{prologue} is copied to the beginning. This is the most convenient
+place to put anything that you want to have in the parser file but which need
+not come before the definition of @code{yyparse}. For example, the
+definitions of @code{yylex} and @code{yyerror} often go here.
+@xref{Interface, ,Parser C-Language Interface}.
If the last section is empty, you may omit the @samp{%%} that separates it
from the grammar rules.
The Bison parser itself contains many static variables whose names start
with @samp{yy} and many macros whose names start with @samp{YY}. It is a
good idea to avoid using any such names (except those documented in this
-manual) in the additional C code section of the grammar file.
+manual) in the epilogue of the grammar file.
@node Symbols, Rules, Grammar Outline, Grammar File
@section Symbols, Terminal and Nonterminal
@item
@cindex string token
@cindex literal string token
-@cindex multi-character literal
+@cindex multicharacter literal
A @dfn{literal string token} is written like a C string constant; for
example, @code{"<="} is a literal string token. A literal string token
doesn't need to be declared unless you need to specify its semantic
-value data type (@pxref{Value Type}), associativity, precedence
+value data type (@pxref{Value Type}), associativity, or precedence
(@pxref{Precedence}).
You can associate the literal string token with a symbolic name as an
By convention, a literal string token is used only to represent a token
that consists of that particular string. Thus, you should use the token
type @code{"<="} to represent the string @samp{<=} as a token. Bison
-does not enforces this convention, but if you depart from it, people who
+does not enforce this convention, but if you depart from it, people who
read your program will be confused.
All the escape sequences used in string literals in C can be used in
the character, so @code{yylex} can use the identical character constant to
generate the requisite code. Each named token type becomes a C macro in
the parser file, so @code{yylex} can use the name to stand for the code.
-(This is why periods don't make sense in terminal symbols.)
+(This is why periods don't make sense in terminal symbols.)
@xref{Calling Convention, ,Calling Convention for @code{yylex}}.
If @code{yylex} is defined in a separate file, you need to arrange for the
@end example
@noindent
-where @var{result} is the nonterminal symbol that this rule describes
+where @var{result} is the nonterminal symbol that this rule describes,
and @var{components} are various terminal and nonterminal symbols that
-are put together by this rule (@pxref{Symbols}).
+are put together by this rule (@pxref{Symbols}).
For example,
A rule is called @dfn{recursive} when its @var{result} nonterminal appears
also on its right hand side. Nearly all Bison grammars need to use
recursion, because that is the only way to define a sequence of any number
-of somethings. Consider this recursive definition of a comma-separated
-sequence of one or more expressions:
+of a particular thing. Consider this recursive definition of a
+comma-separated sequence of one or more expressions:
@example
@group
@dfn{Indirect} or @dfn{mutual} recursion occurs when the result of the
rule does not appear directly on its right hand side, but does appear
in rules for other nonterminals which do appear on its right hand
-side.
+side.
For example:
defines two mutually-recursive nonterminals, since each refers to the
other.
-@node Semantics, Declarations, Recursion, Grammar File
+@node Semantics, Locations, Recursion, Grammar File
@section Defining Language Semantics
@cindex defining language semantics
-@cindex language semantics, defining
+@cindex language semantics, defining
The grammar rules for a language determine only the syntax. The semantics
are determined by the semantic values associated with various tokens and
@end example
@noindent
-This macro definition must go in the C declarations section of the grammar
-file (@pxref{Grammar Outline, ,Outline of a Bison Grammar}).
+This macro definition must go in the prologue of the grammar file
+(@pxref{Grammar Outline, ,Outline of a Bison Grammar}).
@node Multiple Types, Actions, Value Type, Semantics
@subsection More Than One Value Type
@code{%union} Bison declaration (@pxref{Union Decl, ,The Collection of Value Types}).
@item
-Choose one of those types for each symbol (terminal or nonterminal)
-for which semantic values are used. This is done for tokens with the
-@code{%token} Bison declaration (@pxref{Token Decl, ,Token Type Names}) and for groupings
-with the @code{%type} Bison declaration (@pxref{Type Decl, ,Nonterminal Symbols}).
+Choose one of those types for each symbol (terminal or nonterminal) for
+which semantic values are used. This is done for tokens with the
+@code{%token} Bison declaration (@pxref{Token Decl, ,Token Type Names})
+and for groupings with the @code{%type} Bison declaration (@pxref{Type
+Decl, ,Nonterminal Symbols}).
@end itemize
@node Actions, Action Types, Multiple Types, Semantics
its value with an assignment to @code{$$}, and actions later in the rule
can refer to the value using @code{$@var{n}}. Since there is no symbol
to name the action, there is no way to declare a data type for the value
-in advance, so you must use the @samp{$<@dots{}>} construct to specify a
-data type each time you refer to this value.
+in advance, so you must use the @samp{$<@dots{}>@var{n}} construct to
+specify a data type each time you refer to this value.
There is no way to set the value of the entire rule with a mid-rule
action, because assignments to @code{$$} do not have that effect. The
converted to an end-of-rule action in this way, and this is what Bison
actually does to implement mid-rule actions.
-@node Declarations, Multiple Parsers, Semantics, Grammar File
+@node Locations, Declarations, Semantics, Grammar File
+@section Tracking Locations
+@cindex location
+@cindex textual position
+@cindex position, textual
+
+Though grammar rules and semantic actions are enough to write a fully
+functional parser, it can be useful to process some additionnal informations,
+especially symbol locations.
+
+@c (terminal or not) ?
+
+The way locations are handled is defined by providing a data type, and actions
+to take when rules are matched.
+
+@menu
+* Location Type:: Specifying a data type for locations.
+* Actions and Locations:: Using locations in actions.
+* Location Default Action:: Defining a general way to compute locations.
+@end menu
+
+@node Location Type, Actions and Locations, , Locations
+@subsection Data Type of Locations
+@cindex data type of locations
+@cindex default location type
+
+Defining a data type for locations is much simpler than for semantic values,
+since all tokens and groupings always use the same type.
+
+The type of locations is specified by defining a macro called @code{YYLTYPE}.
+When @code{YYLTYPE} is not defined, Bison uses a default structure type with
+four members:
+
+@example
+struct
+@{
+ int first_line;
+ int first_column;
+ int last_line;
+ int last_column;
+@}
+@end example
+
+@node Actions and Locations, Location Default Action, Location Type, Locations
+@subsection Actions and Locations
+@cindex location actions
+@cindex actions, location
+@vindex @@$
+@vindex @@@var{n}
+
+Actions are not only useful for defining language semantics, but also for
+describing the behavior of the output parser with locations.
+
+The most obvious way for building locations of syntactic groupings is very
+similar to the way semantic values are computed. In a given rule, several
+constructs can be used to access the locations of the elements being matched.
+The location of the @var{n}th component of the right hand side is
+@code{@@@var{n}}, while the location of the left hand side grouping is
+@code{@@$}.
+
+Here is a basic example using the default data type for locations:
+
+@example
+@group
+exp: @dots{}
+ | exp '/' exp
+ @{
+ @@$.first_column = @@1.first_column;
+ @@$.first_line = @@1.first_line;
+ @@$.last_column = @@3.last_column;
+ @@$.last_line = @@3.last_line;
+ if ($3)
+ $$ = $1 / $3;
+ else
+ @{
+ $$ = 1;
+ printf("Division by zero, l%d,c%d-l%d,c%d",
+ @@3.first_line, @@3.first_column,
+ @@3.last_line, @@3.last_column);
+ @}
+ @}
+@end group
+@end example
+
+As for semantic values, there is a default action for locations that is
+run each time a rule is matched. It sets the beginning of @code{@@$} to the
+beginning of the first symbol, and the end of @code{@@$} to the end of the
+last symbol.
+
+With this default action, the location tracking can be fully automatic. The
+example above simply rewrites this way:
+
+@example
+@group
+exp: @dots{}
+ | exp '/' exp
+ @{
+ if ($3)
+ $$ = $1 / $3;
+ else
+ @{
+ $$ = 1;
+ printf("Division by zero, l%d,c%d-l%d,c%d",
+ @@3.first_line, @@3.first_column,
+ @@3.last_line, @@3.last_column);
+ @}
+ @}
+@end group
+@end example
+
+@node Location Default Action, , Actions and Locations, Locations
+@subsection Default Action for Locations
+@vindex YYLLOC_DEFAULT
+
+Actually, actions are not the best place to compute locations. Since locations
+are much more general than semantic values, there is room in the output parser
+to redefine the default action to take for each rule. The
+@code{YYLLOC_DEFAULT} macro is called each time a rule is matched, before the
+associated action is run.
+
+Most of the time, this macro is general enough to suppress location
+dedicated code from semantic actions.
+
+The @code{YYLLOC_DEFAULT} macro takes three parameters. The first one is
+the location of the grouping (the result of the computation). The second one
+is an array holding locations of all right hand side elements of the rule
+being matched. The last one is the size of the right hand side rule.
+
+By default, it is defined this way:
+
+@example
+@group
+#define YYLLOC_DEFAULT(Current, Rhs, N) \
+ Current.last_line = Rhs[N].last_line; \
+ Current.last_column = Rhs[N].last_column;
+@end group
+@end example
+
+When defining @code{YYLLOC_DEFAULT}, you should consider that:
+
+@itemize @bullet
+@item
+All arguments are free of side-effects. However, only the first one (the
+result) should be modified by @code{YYLLOC_DEFAULT}.
+
+@item
+Before @code{YYLLOC_DEFAULT} is executed, the output parser sets @code{@@$}
+to @code{@@1}.
+
+@item
+For consistency with semantic actions, valid indexes for the location array
+range from 1 to @var{n}.
+@end itemize
+
+@node Declarations, Multiple Parsers, Locations, Grammar File
@section Bison Declarations
@cindex declarations, Bison
@cindex Bison declarations
the parser, so that the function @code{yylex} (if it is in this file)
can use the name @var{name} to stand for this token type's code.
-Alternatively, you can use @code{%left}, @code{%right}, or @code{%nonassoc}
-instead of @code{%token}, if you wish to specify precedence.
-@xref{Precedence Decl, ,Operator Precedence}.
+Alternatively, you can use @code{%left}, @code{%right}, or
+@code{%nonassoc} instead of @code{%token}, if you wish to specify
+associativity and precedence. @xref{Precedence Decl, ,Operator
+Precedence}.
You can explicitly specify the numeric code for a token type by appending
an integer value in the field immediately following the token name:
In the event that the stack type is a union, you must augment the
@code{%token} or other token declaration to include the data type
-alternative delimited by angle-brackets (@pxref{Multiple Types, ,More Than One Value Type}).
+alternative delimited by angle-brackets (@pxref{Multiple Types, ,More Than One Value Type}).
For example:
The @code{%union} declaration specifies the entire collection of possible
data types for semantic values. The keyword @code{%union} is followed by a
pair of braces containing the same thing that goes inside a @code{union} in
-C.
+C.
For example:
A @dfn{reentrant} program is one which does not alter in the course of
execution; in other words, it consists entirely of @dfn{pure} (read-only)
code. Reentrancy is important whenever asynchronous execution is possible;
-for example, a nonreentrant program may not be safe to call from a signal
-handler. In systems with multiple threads of control, a nonreentrant
+for example, a non-reentrant program may not be safe to call from a signal
+handler. In systems with multiple threads of control, a non-reentrant
program must be called only within interlocks.
Normally, Bison generates a parser which is not reentrant. This is
(@pxref{Type Decl, ,Nonterminal Symbols}).
@item %start
-Specify the grammar's start symbol (@pxref{Start Decl, ,The Start-Symbol}).
+Specify the grammar's start symbol (@pxref{Start Decl, ,The
+Start-Symbol}).
@item %expect
Declare the expected number of shift-reduce conflicts
(@pxref{Expect Decl, ,Suppressing Conflict Warnings}).
+@item %yacc
+@itemx %fixed_output_files
+Pretend the option @option{--yacc} was given, i.e., imitate Yacc,
+including its naming conventions. @xref{Bison Options}, for more.
+
+@item %locations
+Generate the code processing the locations (@pxref{Action Features,
+,Special Features for Use in Actions}). This mode is enabled as soon as
+the grammar uses the special @samp{@@@var{n}} tokens, but if your
+grammar does not use it, using @samp{%locations} allows for more
+accurate parse error messages.
+
@item %pure_parser
-Request a pure (reentrant) parser program (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}).
+Request a pure (reentrant) parser program (@pxref{Pure Decl, ,A Pure
+(Reentrant) Parser}).
+
+@item %no_parser
+Do not include any C code in the parser file; generate tables only. The
+parser file contains just @code{#define} directives and static variable
+declarations.
+
+This option also tells Bison to write the C code for the grammar actions
+into a file named @file{@var{filename}.act}, in the form of a
+brace-surrounded body fit for a @code{switch} statement.
@item %no_lines
Don't generate any @code{#line} preprocessor commands in the parser
associate errors with the parser file, treating it an independent source
file in its own right.
-@item %raw
-The output file @file{@var{name}.h} normally defines the tokens with
-Yacc-compatible token numbers. If this option is specified, the
-internal Bison numbers are used instead. (Yacc-compatible numbers start
-at 257 except for single character tokens; Bison assigns token numbers
-sequentially for all tokens starting at 3.)
+@item %debug
+Output a definition of the macro @code{YYDEBUG} into the parser file, so
+that the debugging facilities are compiled. @xref{Debugging, ,Debugging
+Your Parser}.
+
+@item %defines
+Write an extra output file containing macro definitions for the token
+type names defined in the grammar and the semantic value type
+@code{YYSTYPE}, as well as a few @code{extern} variable declarations.
+
+If the parser output file is named @file{@var{name}.c} then this file
+is named @file{@var{name}.h}.@refill
+
+This output file is essential if you wish to put the definition of
+@code{yylex} in a separate source file, because @code{yylex} needs to
+be able to refer to token type codes and the variable
+@code{yylval}. @xref{Token Values, ,Semantic Values of Tokens}.@refill
+
+@c @item %source_extension
+@c Specify the extension of the parser output file.
+@c
+@c For example, a grammar file named @file{foo.yy} and containing a
+@c @code{%source_extension .cpp} directive will produce a parser file
+@c named @file{foo.tab.cpp}
+@c
+@c @item %header_extension
+@c Specify the extension of the parser header file generated when
+@c @code{%define} or @samp{-d} are used.
+@c
+@c For example, a garmmar file named @file{foo.ypp} and containing a
+@c @code{%header_extension .hh} directive will produce a header file
+@c named @file{foo.tab.hh}
+
+@item %verbose
+Write an extra output file containing verbose descriptions of the
+parser states and what is done for each type of look-ahead token in
+that state.
+
+This file also describes all the conflicts, both those resolved by
+operator precedence and the unresolved ones.
+
+The file's name is made by removing @samp{.tab.c} or @samp{.c} from
+the parser output file name, and adding @samp{.output} instead.@refill
+
+Therefore, if the input file is @file{foo.y}, then the parser file is
+called @file{foo.tab.c} by default. As a consequence, the verbose
+output file is called @file{foo.output}.@refill
@item %token_table
Generate an array of token names in the parser file. The name of the
@item YYNTOKENS
The highest token number, plus one.
@item YYNNTS
-The number of non-terminal symbols.
+The number of nonterminal symbols.
@item YYNRULES
The number of grammar rules,
@item YYNSTATES
Keep in mind that the parser uses many C identifiers starting with
@samp{yy} and @samp{YY} for internal purposes. If you use such an
-identifier (aside from those in this manual) in an action or in additional
-C code in the grammar file, you are likely to run into trouble.
+identifier (aside from those in this manual) in an action or in epilogue
+in the grammar file, you are likely to run into trouble.
@menu
* Parser Function:: How to call @code{yyparse} and what it returns.
-* Lexical:: You must supply a function @code{yylex}
+* Lexical:: You must supply a function @code{yylex}
which reads tokens.
* Error Reporting:: You must supply a function @code{yyerror}.
* Action Features:: Special features for use in actions.
You call the function @code{yyparse} to cause parsing to occur. This
function reads tokens, executes actions, and ultimately returns when it
encounters end-of-input or an unrecoverable syntax error. You can also
-write an action which directs @code{yyparse} to return immediately without
-reading further.
+write an action which directs @code{yyparse} to return immediately
+without reading further.
The value returned by @code{yyparse} is 0 if parsing was successful (return
is due to end-of-input).
Here is an example showing these things:
@example
-yylex ()
+int
+yylex (void)
@{
@dots{}
if (c == EOF) /* Detect end of file. */
the grammar file has no effect on @code{yylex}.
@item
-@code{yylex} can find the multi-character token in the @code{yytname}
+@code{yylex} can find the multicharacter token in the @code{yytname}
table. The index of the token in the table is the token type's code.
-The name of a multi-character token is recorded in @code{yytname} with a
+The name of a multicharacter token is recorded in @code{yytname} with a
double-quote, the token's characters, and another double-quote. The
token's characters are not escaped in any way; they appear verbatim in
the contents of the string in the table.
@{
if (yytname[i] != 0
&& yytname[i][0] == '"'
- && strncmp (yytname[i] + 1, token_buffer, strlen (token_buffer))
+ && strncmp (yytname[i] + 1, token_buffer,
+ strlen (token_buffer))
&& yytname[i][strlen (token_buffer) + 1] == '"'
&& yytname[i][strlen (token_buffer) + 2] == 0)
break;
@subsection Semantic Values of Tokens
@vindex yylval
-In an ordinary (nonreentrant) parser, the semantic value of the token must
+In an ordinary (non-reentrant) parser, the semantic value of the token must
be stored into the global variable @code{yylval}. When you are using
just one data type for semantic values, @code{yylval} has that type.
Thus, if the type is @code{int} (the default), you might write this in
@subsection Textual Positions of Tokens
@vindex yylloc
-If you are using the @samp{@@@var{n}}-feature (@pxref{Action Features, ,Special Features for Use in Actions}) in
-actions to keep track of the textual locations of tokens and groupings,
-then you must provide this information in @code{yylex}. The function
-@code{yyparse} expects to find the textual location of a token just parsed
-in the global variable @code{yylloc}. So @code{yylex} must store the
-proper data in that variable. The value of @code{yylloc} is a structure
-and you need only initialize the members that are going to be used by the
-actions. The four members are called @code{first_line},
-@code{first_column}, @code{last_line} and @code{last_column}. Note that
-the use of this feature makes the parser noticeably slower.
+If you are using the @samp{@@@var{n}}-feature (@pxref{Locations, ,
+Tracking Locations}) in actions to keep track of the
+textual locations of tokens and groupings, then you must provide this
+information in @code{yylex}. The function @code{yyparse} expects to
+find the textual location of a token just parsed in the global variable
+@code{yylloc}. So @code{yylex} must store the proper data in that
+variable.
+
+By default, the value of @code{yylloc} is a structure and you need only
+initialize the members that are going to be used by the actions. The
+four members are called @code{first_line}, @code{first_column},
+@code{last_line} and @code{last_column}. Note that the use of this
+feature makes the parser noticeably slower.
@tindex YYLTYPE
The data type of @code{yylloc} has the name @code{YYLTYPE}.
pointers.
@example
-yylex (lvalp, llocp)
- YYSTYPE *lvalp;
- YYLTYPE *llocp;
+int
+yylex (YYSTYPE *lvalp, YYLTYPE *llocp)
@{
@dots{}
*lvalp = value; /* Put value onto Bison stack. */
@cindex syntax error
The Bison parser detects a @dfn{parse error} or @dfn{syntax error}
-whenever it reads a token which cannot satisfy any syntax rule. A
+whenever it reads a token which cannot satisfy any syntax rule. An
action in the grammar can also explicitly proclaim an error, using the
-macro @code{YYERROR} (@pxref{Action Features, ,Special Features for Use in Actions}).
+macro @code{YYERROR} (@pxref{Action Features, ,Special Features for Use
+in Actions}).
The Bison parser expects to report the error by calling an error
reporting function named @code{yyerror}, which you must supply. It is
@findex YYERROR_VERBOSE
If you define the macro @code{YYERROR_VERBOSE} in the Bison declarations
-section (@pxref{Bison Declarations, ,The Bison Declarations Section}), then Bison provides a more verbose
-and specific error message string instead of just plain @w{@code{"parse
-error"}}. It doesn't matter what definition you use for
-@code{YYERROR_VERBOSE}, just whether you define it.
+section (@pxref{Bison Declarations, ,The Bison Declarations Section}),
+then Bison provides a more verbose and specific error message string
+instead of just plain @w{@code{"parse error"}}. It doesn't matter what
+definition you use for @code{YYERROR_VERBOSE}, just whether you define
+it.
The parser can detect one other kind of error: stack overflow. This
happens when the input contains constructions that are very deeply
@example
@group
-yyerror (s)
- char *s;
+void
+yyerror (char *s)
@{
@end group
@group
@item $<@var{typealt}>@var{n}
Like @code{$@var{n}} but specifies alternative @var{typealt} in the
-union specified by the @code{%union} declaration.
+union specified by the @code{%union} declaration.
@xref{Action Types, ,Data Types of Values in Actions}.@refill
@item YYABORT;
@item yyerrok;
Resume generating error messages immediately for subsequent syntax
-errors. This is useful primarily in error rules.
+errors. This is useful primarily in error rules.
@xref{Error Recovery}.
-@item @@@var{n}
-@findex @@@var{n}
-Acts like a structure variable containing information on the line
-numbers and column numbers of the @var{n}th component of the current
-rule. The structure has four members, like this:
+@item @@$
+@findex @@$
+Acts like a structure variable containing information on the textual position
+of the grouping made by the current rule. @xref{Locations, ,
+Tracking Locations}.
-@example
-struct @{
- int first_line, last_line;
- int first_column, last_column;
-@};
-@end example
+@c Check if those paragraphs are still useful or not.
+
+@c @example
+@c struct @{
+@c int first_line, last_line;
+@c int first_column, last_column;
+@c @};
+@c @end example
+
+@c Thus, to get the starting line number of the third component, you would
+@c use @samp{@@3.first_line}.
-Thus, to get the starting line number of the third component, use
-@samp{@@3.first_line}.
+@c In order for the members of this structure to contain valid information,
+@c you must make @code{yylex} supply this information about each token.
+@c If you need only certain members, then @code{yylex} need only fill in
+@c those members.
-In order for the members of this structure to contain valid information,
-you must make @code{yylex} supply this information about each token.
-If you need only certain members, then @code{yylex} need only fill in
-those members.
+@c The use of this feature makes the parser noticeably slower.
+
+@item @@@var{n}
+@findex @@@var{n}
+Acts like a structure variable containing information on the textual position
+of the @var{n}th component of the current rule. @xref{Locations, ,
+Tracking Locations}.
-The use of this feature makes the parser noticeably slower.
@end table
@node Algorithm, Error Recovery, Interface, Top
-@chapter The Bison Parser Algorithm
-@cindex Bison parser algorithm
+@chapter The Bison Parser Algorithm
+@cindex Bison parser algorithm
@cindex algorithm of parser
@cindex shifting
@cindex reduction
@noindent
Suppose the parser has seen the tokens @samp{1}, @samp{-} and @samp{2};
-should it reduce them via the rule for the addition operator? It depends
-on the next token. Of course, if the next token is @samp{)}, we must
-reduce; shifting is invalid because no single rule can reduce the token
-sequence @w{@samp{- 2 )}} or anything starting with that. But if the next
-token is @samp{*} or @samp{<}, we have a choice: either shifting or
-reduction would allow the parse to complete, but with different
-results.
-
-To decide which one Bison should do, we must consider the
-results. If the next operator token @var{op} is shifted, then it
-must be reduced first in order to permit another opportunity to
-reduce the sum. The result is (in effect) @w{@samp{1 - (2
-@var{op} 3)}}. On the other hand, if the subtraction is reduced
-before shifting @var{op}, the result is @w{@samp{(1 - 2) @var{op}
-3}}. Clearly, then, the choice of shift or reduce should depend
-on the relative precedence of the operators @samp{-} and
-@var{op}: @samp{*} should be shifted first, but not @samp{<}.
+should it reduce them via the rule for the subtraction operator? It
+depends on the next token. Of course, if the next token is @samp{)}, we
+must reduce; shifting is invalid because no single rule can reduce the
+token sequence @w{@samp{- 2 )}} or anything starting with that. But if
+the next token is @samp{*} or @samp{<}, we have a choice: either
+shifting or reduction would allow the parse to complete, but with
+different results.
+
+To decide which one Bison should do, we must consider the results. If
+the next operator token @var{op} is shifted, then it must be reduced
+first in order to permit another opportunity to reduce the difference.
+The result is (in effect) @w{@samp{1 - (2 @var{op} 3)}}. On the other
+hand, if the subtraction is reduced before shifting @var{op}, the result
+is @w{@samp{(1 - 2) @var{op} 3}}. Clearly, then, the choice of shift or
+reduce should depend on the relative precedence of the operators
+@samp{-} and @var{op}: @samp{*} should be shifted first, but not
+@samp{<}.
@cindex associativity
What about input such as @w{@samp{1 - 2 - 5}}; should this be
-@w{@samp{(1 - 2) - 5}} or should it be @w{@samp{1 - (2 - 5)}}? For
-most operators we prefer the former, which is called @dfn{left
-association}. The latter alternative, @dfn{right association}, is
-desirable for assignment operators. The choice of left or right
-association is a matter of whether the parser chooses to shift or
-reduce when the stack contains @w{@samp{1 - 2}} and the look-ahead
-token is @samp{-}: shifting makes right-associativity.
+@w{@samp{(1 - 2) - 5}} or should it be @w{@samp{1 - (2 - 5)}}? For most
+operators we prefer the former, which is called @dfn{left association}.
+The latter alternative, @dfn{right association}, is desirable for
+assignment operators. The choice of left or right association is a
+matter of whether the parser chooses to shift or reduce when the stack
+contains @w{@samp{1 - 2}} and the look-ahead token is @samp{-}: shifting
+makes right-associativity.
@node Using Precedence, Precedence Examples, Why Precedence, Precedence
@subsection Specifying Operator Precedence
@end example
It would seem that this grammar can be parsed with only a single token
-of look-ahead: when a @code{param_spec} is being read, an @code{ID} is
+of look-ahead: when a @code{param_spec} is being read, an @code{ID} is
a @code{name} if a comma or colon follows, or a @code{type} if another
@code{ID} follows. In other words, this grammar is LR(1).
is always defined (you need not declare it) and reserved for error
handling. The Bison parser generates an @code{error} token whenever a
syntax error happens; if you have provided a rule to recognize this token
-in the current context, the parse can continue.
+in the current context, the parse can continue.
For example:
Unfortunately, the name being declared is separated from the declaration
construct itself by a complicated syntactic structure---the ``declarator''.
-As a result, the part of Bison parser for C needs to be duplicated, with
-all the nonterminal names changed: once for parsing a declaration in which
-a typedef name can be redefined, and once for parsing a declaration in
-which that can't be done. Here is a part of the duplication, with actions
-omitted for brevity:
+As a result, part of the Bison parser for C needs to be duplicated, with
+all the nonterminal names changed: once for parsing a declaration in
+which a typedef name can be redefined, and once for parsing a
+declaration in which that can't be done. Here is a part of the
+duplication, with actions omitted for brevity:
@example
initdcl:
it is nonzero, all integers are parsed in hexadecimal, and tokens starting
with letters are parsed as integers if possible.
-The declaration of @code{hexflag} shown in the C declarations section of
-the parser file is needed to make it accessible to the actions
-(@pxref{C Declarations, ,The C Declarations Section}). You must also write the code in @code{yylex}
-to obey the flag.
+The declaration of @code{hexflag} shown in the prologue of the parser file
+is needed to make it accessible to the actions (@pxref{Prologue, ,The Prologue}).
+You must also write the code in @code{yylex} to obey the flag.
@node Tie-in Recovery, , Lexical Tie-ins, Context Dependency
@section Lexical Tie-ins and Error Recovery
runs, the @code{yydebug} parser-trace feature can help you figure out why.
To enable compilation of trace facilities, you must define the macro
-@code{YYDEBUG} when you compile the parser. You could use
-@samp{-DYYDEBUG=1} as a compiler option or you could put @samp{#define
-YYDEBUG 1} in the C declarations section of the grammar file
-(@pxref{C Declarations, ,The C Declarations Section}). Alternatively, use the @samp{-t} option when
-you run Bison (@pxref{Invocation, ,Invoking Bison}). We always define @code{YYDEBUG} so that
-debugging is always possible.
+@code{YYDEBUG} when you compile the parser. You could use @samp{-DYYDEBUG=1}
+as a compiler option or you could put @samp{#define YYDEBUG 1} in the prologue
+of the grammar file (@pxref{Prologue, , The Prologue}). Alternatively, use the
+@samp{-t} option when you run Bison (@pxref{Invocation, ,Invoking Bison}).
+We always define @code{YYDEBUG} so that debugging is always possible.
-The trace facility uses @code{stderr}, so you must add @w{@code{#include
-<stdio.h>}} to the C declarations section unless it is already there.
+The trace facility uses @code{stderr}, so you must add
+@w{@code{#include <stdio.h>}} to the prologue unless it is already there.
Once you have compiled the program with trace facilities, the way to
request a trace is to store a nonzero value in the variable @code{yydebug}.
#define YYPRINT(file, type, value) yyprint (file, type, value)
static void
-yyprint (file, type, value)
- FILE *file;
- int type;
- YYSTYPE value;
+yyprint (FILE *file, int type, YYSTYPE value)
@{
if (type == VAR)
fprintf (file, " %s", value.tptr->name);
@samp{.y}. The parser file's name is made by replacing the @samp{.y}
with @samp{.tab.c}. Thus, the @samp{bison foo.y} filename yields
@file{foo.tab.c}, and the @samp{bison hack/foo.y} filename yields
-@file{hack/foo.tab.c}.@refill
+@file{hack/foo.tab.c}. It's is also possible, in case you are writting
+C++ code instead of C in your grammar file, to name it @file{foo.ypp}
+or @file{foo.y++}. Then, the output files will take an extention like
+the given one as input (repectively @file{foo.tab.cpp} and @file{foo.tab.c++}).
+This feature takes effect with all options that manipulate filenames like
+@samp{-o} or @samp{-d}.
+
+For example :
+
+@example
+bison -d @var{infile.yxx}
+@end example
+@noindent
+will produce @file{infile.tab.cxx} and @file{infile.tab.hxx}. and
+
+@example
+bison -d @var{infile.y} -o @var{output.c++}
+@end example
+@noindent
+will produce @file{output.c++} and @file{outfile.h++}.
+
@menu
-* Bison Options:: All the options described in detail,
+* Bison Options:: All the options described in detail,
in alphabetical order by short options.
+* Environment Variables:: Variables which affect Bison execution.
* Option Cross Key:: Alphabetical list of long options.
* VMS Invocation:: Bison command syntax on VMS.
@end menu
-@node Bison Options, Option Cross Key, , Invocation
+@node Bison Options, Environment Variables, , Invocation
@section Bison Options
Bison supports both traditional single-letter options and mnemonic long
short option. It is followed by a cross key alphabetized by long
option.
-@table @samp
-@item -b @var{file-prefix}
-@itemx --file-prefix=@var{prefix}
-Specify a prefix to use for all Bison output file names. The names are
-chosen as if the input file were named @file{@var{prefix}.c}.
-
-@item -d
-@itemx --defines
-Write an extra output file containing macro definitions for the token
-type names defined in the grammar and the semantic value type
-@code{YYSTYPE}, as well as a few @code{extern} variable declarations.
+@c Please, keep this ordered as in `bison --help'.
+@noindent
+Operations modes:
+@table @option
+@item -h
+@itemx --help
+Print a summary of the command-line options to Bison and exit.
-If the parser output file is named @file{@var{name}.c} then this file
-is named @file{@var{name}.h}.@refill
+@item -V
+@itemx --version
+Print the version number of Bison and exit.
-This output file is essential if you wish to put the definition of
-@code{yylex} in a separate source file, because @code{yylex} needs to
-be able to refer to token type codes and the variable
-@code{yylval}. @xref{Token Values, ,Semantic Values of Tokens}.@refill
+@need 1750
+@item -y
+@itemx --yacc
+@itemx --fixed-output-files
+Equivalent to @samp{-o y.tab.c}; the parser output file is called
+@file{y.tab.c}, and the other outputs are called @file{y.output} and
+@file{y.tab.h}. The purpose of this option is to imitate Yacc's output
+file name conventions. Thus, the following shell script can substitute
+for Yacc:@refill
-@item -l
-@itemx --no-lines
-Don't put any @code{#line} preprocessor commands in the parser file.
-Ordinarily Bison puts them in the parser file so that the C compiler
-and debuggers will associate errors with your source file, the
-grammar file. This option causes them to associate errors with the
-parser file, treating it as an independent source file in its own right.
+@example
+bison -y $*
+@end example
+@end table
-@item -n
-@itemx --no-parser
-Do not include any C code in the parser file; generate tables only. The
-parser file contains just @code{#define} directives and static variable
-declarations.
+@noindent
+Tuning the parser:
-This option also tells Bison to write the C code for the grammar actions
-into a file named @file{@var{filename}.act}, in the form of a
-brace-surrounded body fit for a @code{switch} statement.
+@table @option
+@item -S @var{file}
+@itemx --skeleton=@var{file}
+Specify the skeleton to use. You probably don't need this option unless
+you are developing Bison.
-@item -o @var{outfile}
-@itemx --output-file=@var{outfile}
-Specify the name @var{outfile} for the parser file.
+@item -t
+@itemx --debug
+Output a definition of the macro @code{YYDEBUG} into the parser file, so
+that the debugging facilities are compiled. @xref{Debugging, ,Debugging
+Your Parser}.
-The other output files' names are constructed from @var{outfile}
-as described under the @samp{-v} and @samp{-d} options.
+@item --locations
+Pretend that @code{%locactions} was specified. @xref{Decl Summary}.
@item -p @var{prefix}
@itemx --name-prefix=@var{prefix}
@xref{Multiple Parsers, ,Multiple Parsers in the Same Program}.
-@item -r
-@itemx --raw
-Pretend that @code{%raw} was specified. @xref{Decl Summary}.
+@item -l
+@itemx --no-lines
+Don't put any @code{#line} preprocessor commands in the parser file.
+Ordinarily Bison puts them in the parser file so that the C compiler
+and debuggers will associate errors with your source file, the
+grammar file. This option causes them to associate errors with the
+parser file, treating it as an independent source file in its own right.
-@item -t
-@itemx --debug
-Output a definition of the macro @code{YYDEBUG} into the parser file,
-so that the debugging facilities are compiled. @xref{Debugging, ,Debugging Your Parser}.
+@item -n
+@itemx --no-parser
+Pretend that @code{%no_parser} was specified. @xref{Decl Summary}.
+
+@item -k
+@itemx --token-table
+Pretend that @code{%token_table} was specified. @xref{Decl Summary}.
+@end table
+
+@noindent
+Adjust the output:
+
+@table @option
+@item -d
+@itemx --defines
+Pretend that @code{%verbose} was specified, i.e., write an extra output
+file containing macro definitions for the token type names defined in
+the grammar and the semantic value type @code{YYSTYPE}, as well as a few
+@code{extern} variable declarations. @xref{Decl Summary}.
+
+@item -b @var{file-prefix}
+@itemx --file-prefix=@var{prefix}
+Specify a prefix to use for all Bison output file names. The names are
+chosen as if the input file were named @file{@var{prefix}.c}.
@item -v
@itemx --verbose
-Write an extra output file containing verbose descriptions of the
-parser states and what is done for each type of look-ahead token in
-that state.
-
-This file also describes all the conflicts, both those resolved by
-operator precedence and the unresolved ones.
+Pretend that @code{%verbose} was specified, i.e, write an extra output
+file containing verbose descriptions of the grammar and
+parser. @xref{Decl Summary}, for more.
-The file's name is made by removing @samp{.tab.c} or @samp{.c} from
-the parser output file name, and adding @samp{.output} instead.@refill
+@item -o @var{outfile}
+@itemx --output-file=@var{outfile}
+Specify the name @var{outfile} for the parser file.
-Therefore, if the input file is @file{foo.y}, then the parser file is
-called @file{foo.tab.c} by default. As a consequence, the verbose
-output file is called @file{foo.output}.@refill
+The other output files' names are constructed from @var{outfile}
+as described under the @samp{-v} and @samp{-d} options.
+@end table
-@item -V
-@itemx --version
-Print the version number of Bison and exit.
+@node Environment Variables, Option Cross Key, Bison Options, Invocation
+@section Environment Variables
+@cindex environment variables
+@cindex BISON_HAIRY
+@cindex BISON_SIMPLE
-@item -h
-@itemx --help
-Print a summary of the command-line options to Bison and exit.
+Here is a list of environment variables which affect the way Bison
+runs.
-@need 1750
-@item -y
-@itemx --yacc
-@itemx --fixed-output-files
-Equivalent to @samp{-o y.tab.c}; the parser output file is called
-@file{y.tab.c}, and the other outputs are called @file{y.output} and
-@file{y.tab.h}. The purpose of this option is to imitate Yacc's output
-file name conventions. Thus, the following shell script can substitute
-for Yacc:@refill
+@table @samp
+@item BISON_SIMPLE
+@itemx BISON_HAIRY
+Much of the parser generated by Bison is copied verbatim from a file
+called @file{bison.simple}. If Bison cannot find that file, or if you
+would like to direct Bison to use a different copy, setting the
+environment variable @code{BISON_SIMPLE} to the path of the file will
+cause Bison to use that copy instead.
+
+When the @samp{%semantic_parser} declaration is used, Bison copies from
+a file called @file{bison.hairy} instead. The location of this file can
+also be specified or overridden in a similar fashion, with the
+@code{BISON_HAIRY} environment variable.
-@example
-bison -y $*
-@end example
@end table
-@node Option Cross Key, VMS Invocation, Bison Options, Invocation
+@node Option Cross Key, VMS Invocation, Environment Variables, Invocation
@section Option Cross Key
Here is a list of options, alphabetized by long option, to help you find
\line{ --no-lines \leaderfill -l}
\line{ --no-parser \leaderfill -n}
\line{ --output-file \leaderfill -o}
-\line{ --raw \leaderfill -r}
\line{ --token-table \leaderfill -k}
\line{ --verbose \leaderfill -v}
\line{ --version \leaderfill -V}
--no-lines -l
--no-parser -n
--output-file=@var{outfile} -o @var{outfile}
---raw -r
--token-table -k
--verbose -v
--version -V
@item YYABORT
Macro to pretend that an unrecoverable syntax error has occurred, by
making @code{yyparse} return 1 immediately. The error reporting
-function @code{yyerror} is not called. @xref{Parser Function, ,The Parser Function @code{yyparse}}.
+function @code{yyerror} is not called. @xref{Parser Function, ,The
+Parser Function @code{yyparse}}.
@item YYACCEPT
Macro to pretend that a complete utterance of the language has been
-read, by making @code{yyparse} return 0 immediately.
+read, by making @code{yyparse} return 0 immediately.
@xref{Parser Function, ,The Parser Function @code{yyparse}}.
@item YYBACKUP
@item YYLTYPE
Macro for the data type of @code{yylloc}; a structure with four
-members. @xref{Token Positions, ,Textual Positions of Tokens}.
+members. @xref{Location Type, , Data Types of Locations}.
@item yyltype
Default value for YYLTYPE.
Macro whose value indicates whether the parser is recovering from a
syntax error. @xref{Action Features, ,Special Features for Use in Actions}.
+@item YYSTACK_USE_ALLOCA
+Macro used to control the use of @code{alloca}. If defined to @samp{0},
+the parser will not use @code{alloca} but @code{malloc} when trying to
+grow its internal stacks. Do @emph{not} define @code{YYSTACK_USE_ALLOCA}
+to anything else.
+
@item YYSTYPE
Macro for the data type of semantic values; @code{int} by default.
@xref{Value Type, ,Data Types of Semantic Values}.
@item yychar
-External integer variable that contains the integer value of the
-current look-ahead token. (In a pure parser, it is a local variable
-within @code{yyparse}.) Error-recovery rule actions may examine this
-variable. @xref{Action Features, ,Special Features for Use in Actions}.
+External integer variable that contains the integer value of the current
+look-ahead token. (In a pure parser, it is a local variable within
+@code{yyparse}.) Error-recovery rule actions may examine this variable.
+@xref{Action Features, ,Special Features for Use in Actions}.
@item yyclearin
Macro used in error-recovery rule actions. It clears the previous
@item yyerror
User-supplied function to be called by @code{yyparse} on error. The
function receives one argument, a pointer to a character string
-containing an error message. @xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}.
+containing an error message. @xref{Error Reporting, ,The Error
+Reporting Function @code{yyerror}}.
@item yylex
User-supplied lexical analyzer function, called with no arguments
@code{yylex}.) @xref{Token Values, ,Semantic Values of Tokens}.
@item yylloc
-External variable in which @code{yylex} should place the line and
-column numbers associated with a token. (In a pure parser, it is a
-local variable within @code{yyparse}, and its address is passed to
+External variable in which @code{yylex} should place the line and column
+numbers associated with a token. (In a pure parser, it is a local
+variable within @code{yyparse}, and its address is passed to
@code{yylex}.) You can ignore this variable if you don't use the
-@samp{@@} feature in the grammar actions. @xref{Token Positions, ,Textual Positions of Tokens}.
+@samp{@@} feature in the grammar actions. @xref{Token Positions,
+,Textual Positions of Tokens}.
@item yynerrs
-Global variable which Bison increments each time there is a parse
-error. (In a pure parser, it is a local variable within
-@code{yyparse}.) @xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}.
+Global variable which Bison increments each time there is a parse error.
+(In a pure parser, it is a local variable within @code{yyparse}.)
+@xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}.
@item yyparse
The parser function produced by Bison; call this function to start
parsing. @xref{Parser Function, ,The Parser Function @code{yyparse}}.
+@item %debug
+Equip the parser for debugging. @xref{Decl Summary}.
+
+@item %defines
+Bison declaration to create a header file meant for the scanner.
+@xref{Decl Summary}.
+
+@c @item %source_extension
+@c Bison declaration to specify the generated parser output file extension.
+@c @xref{Decl Summary}.
+@c
+@c @item %header_extension
+@c Bison declaration to specify the generated parser header file extension
+@c if required. @xref{Decl Summary}.
+
@item %left
Bison declaration to assign left associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
parser file. @xref{Decl Summary}.
@item %nonassoc
-Bison declaration to assign nonassociativity to token(s).
+Bison declaration to assign non-associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
@item %prec
Bison declaration to request a pure (reentrant) parser.
@xref{Pure Decl, ,A Pure (Reentrant) Parser}.
-@item %raw
-Bison declaration to use Bison internal token code numbers in token
-tables instead of the usual Yacc-compatible token code numbers.
-@xref{Decl Summary}.
-
@item %right
Bison declaration to assign right associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
@table @samp
@item %%
Delimiter used to separate the grammar rule section from the
-Bison declarations section or the additional C code section.
+Bison declarations section or the epilogue.
@xref{Grammar Layout, ,The Overall Layout of a Bison Grammar}.
@item %@{ %@}
-All code listed between @samp{%@{} and @samp{%@}} is copied directly
-to the output file uninterpreted. Such code forms the ``C
-declarations'' section of the input file. @xref{Grammar Outline, ,Outline of a Bison Grammar}.
+All code listed between @samp{%@{} and @samp{%@}} is copied directly to
+the output file uninterpreted. Such code forms the prologue of the input
+file. @xref{Grammar Outline, ,Outline of a Bison
+Grammar}.
@item /*@dots{}*/
Comment delimiters, as in C.
@item :
-Separates a rule's result from its components. @xref{Rules, ,Syntax of Grammar Rules}.
+Separates a rule's result from its components. @xref{Rules, ,Syntax of
+Grammar Rules}.
@item ;
Terminates a rule. @xref{Rules, ,Syntax of Grammar Rules}.
@xref{Rules, ,Syntax of Grammar Rules}.
@end table
-@node Glossary, Index, Table of Symbols, Top
+@node Glossary, Copying This Manual, Table of Symbols, Top
@appendix Glossary
@cindex glossary
@table @asis
@item Backus-Naur Form (BNF)
Formal method of specifying context-free grammars. BNF was first used
-in the @cite{ALGOL-60} report, 1963. @xref{Language and Grammar, ,Languages and Context-Free Grammars}.
+in the @cite{ALGOL-60} report, 1963. @xref{Language and Grammar,
+,Languages and Context-Free Grammars}.
@item Context-free grammars
Grammars specified as rules that can be applied regardless of context.
Thus, if there is a rule which says that an integer can be used as an
expression, integers are allowed @emph{anywhere} an expression is
-permitted. @xref{Language and Grammar, ,Languages and Context-Free Grammars}.
+permitted. @xref{Language and Grammar, ,Languages and Context-Free
+Grammars}.
@item Dynamic allocation
Allocation of memory that occurs during execution, rather than at
@item Grouping
A language construct that is (in general) grammatically divisible;
-for example, `expression' or `declaration' in C.
+for example, `expression' or `declaration' in C.
@xref{Language and Grammar, ,Languages and Context-Free Grammars}.
@item Infix operator
@samp{c}. @xref{Precedence, ,Operator Precedence}.
@item Left recursion
-A rule whose result symbol is also its first component symbol;
-for example, @samp{expseq1 : expseq1 ',' exp;}. @xref{Recursion, ,Recursive Rules}.
+A rule whose result symbol is also its first component symbol; for
+example, @samp{expseq1 : expseq1 ',' exp;}. @xref{Recursion, ,Recursive
+Rules}.
@item Left-to-right parsing
Parsing a sentence of a language by analyzing it token by token from
tokens are parsed. @xref{Lexical Tie-ins}.
@item Literal string token
-A token which constists of two or more fixed characters.
-@xref{Symbols}.
+A token which consists of two or more fixed characters. @xref{Symbols}.
@item Look-ahead token
-A token already read but not yet shifted. @xref{Look-Ahead, ,Look-Ahead Tokens}.
+A token already read but not yet shifted. @xref{Look-Ahead, ,Look-Ahead
+Tokens}.
@item LALR(1)
The class of context-free grammars that Bison (like most other parser
@item Reduction
Replacing a string of nonterminals and/or terminals with a single
-nonterminal, according to a grammar rule. @xref{Algorithm, ,The Bison Parser Algorithm }.
+nonterminal, according to a grammar rule. @xref{Algorithm, ,The Bison
+Parser Algorithm }.
@item Reentrant
A reentrant subprogram is a subprogram which can be in invoked any
A language in which all operators are postfix operators.
@item Right recursion
-A rule whose result symbol is also its last component symbol;
-for example, @samp{expseq1: exp ',' expseq1;}. @xref{Recursion, ,Recursive Rules}.
+A rule whose result symbol is also its last component symbol; for
+example, @samp{expseq1: exp ',' expseq1;}. @xref{Recursion, ,Recursive
+Rules}.
@item Semantics
In computer languages, the semantics are specified by the actions
@item Start symbol
The nonterminal symbol that stands for a complete valid utterance in
the language being parsed. The start symbol is usually listed as the
-first nonterminal symbol in a language specification.
+first nonterminal symbol in a language specification.
@xref{Start Decl, ,The Start-Symbol}.
@item Symbol table
the lexical analyzer. @xref{Symbols}.
@item Terminal symbol
-A grammar symbol that has no rules in the grammar and therefore
-is grammatically indivisible. The piece of text it represents
-is a token. @xref{Language and Grammar, ,Languages and Context-Free Grammars}.
+A grammar symbol that has no rules in the grammar and therefore is
+grammatically indivisible. The piece of text it represents is a token.
+@xref{Language and Grammar, ,Languages and Context-Free Grammars}.
@end table
-@node Index, , Glossary, Top
-@unnumbered Index
-
-@printindex cp
-
-@contents
-
-@bye
-
-
-\f
+@node Copying This Manual, Index, Glossary, Top
+@appendix Copying This Manual
-@c old menu
+@menu
+* GNU Free Documentation License:: License for copying this manual.
+@end menu
-* Introduction::
-* Conditions::
-* Copying:: The GNU General Public License says
- how you can copy and share Bison
+@include fdl.texi
-Tutorial sections:
-* Concepts:: Basic concepts for understanding Bison.
-* Examples:: Three simple explained examples of using Bison.
+@node Index, , Copying This Manual, Top
+@unnumbered Index
-Reference sections:
-* Grammar File:: Writing Bison declarations and rules.
-* Interface:: C-language interface to the parser function @code{yyparse}.
-* Algorithm:: How the Bison parser works at run-time.
-* Error Recovery:: Writing rules for error recovery.
-* Context Dependency::What to do if your language syntax is too
- messy for Bison to handle straightforwardly.
-* Debugging:: Debugging Bison parsers that parse wrong.
-* Invocation:: How to run Bison (to produce the parser source file).
-* Table of Symbols:: All the keywords of the Bison language are explained.
-* Glossary:: Basic concepts are explained.
-* Index:: Cross-references to the text.
+@printindex cp
+@bye
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