@value{UPDATED}), the @acronym{GNU} parser generator.
Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998,
-1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
+1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the @acronym{GNU} Free Documentation License,
-Version 1.1 or any later version published by the Free Software
+Version 1.2 or any later version published by the Free Software
Foundation; with no Invariant Sections, with the Front-Cover texts
being ``A @acronym{GNU} Manual,'' and with the Back-Cover Texts as in
(a) below. A copy of the license is included in the section entitled
@end quotation
@end copying
-@dircategory GNU programming tools
+@dircategory Software development
@direntry
* bison: (bison). @acronym{GNU} parser generator (Yacc replacement).
@end direntry
@insertcopying
@sp 2
Published by the Free Software Foundation @*
-59 Temple Place, Suite 330 @*
-Boston, MA 02111-1307 USA @*
+51 Franklin Street, Fifth Floor @*
+Boston, MA 02110-1301 USA @*
Printed copies are available from the Free Software Foundation.@*
@acronym{ISBN} 1-882114-44-2
@sp 2
* Precedence Decl:: Declaring terminals with precedence and associativity.
* Union Decl:: Declaring the set of all semantic value types.
* Type Decl:: Declaring the choice of type for a nonterminal symbol.
+* Initial Action Decl:: Code run before parsing starts.
* Destructor Decl:: Declaring how symbols are freed.
* Expect Decl:: Suppressing warnings about parsing conflicts.
* Start Decl:: Specifying the start symbol.
uniquely determined by the preceding input and a fixed, finite portion
(called a @dfn{look-ahead}) of the remaining input. A context-free
grammar can be @dfn{ambiguous}, meaning that there are multiple ways to
-apply the grammar rules to get the some inputs. Even unambiguous
+apply the grammar rules to get the same inputs. Even unambiguous
grammars can be @dfn{non-deterministic}, meaning that no fixed
look-ahead always suffices to determine the next grammar rule to apply.
With the proper declarations, Bison is also able to parse these more
@ifinfo
@example
int /* @r{keyword `int'} */
-square (int x) /* @r{identifier, open-paren, identifier,}
+square (int x) /* @r{identifier, open-paren, keyword `int',}
@r{identifier, close-paren} */
@{ /* @r{open-brace} */
return x * x; /* @r{keyword `return', identifier, asterisk,
@ifnotinfo
@example
int /* @r{keyword `int'} */
-square (int x) /* @r{identifier, open-paren, identifier, identifier, close-paren} */
+square (int x) /* @r{identifier, open-paren, keyword `int', identifier, close-paren} */
@{ /* @r{open-brace} */
return x * x; /* @r{keyword `return', identifier, asterisk, identifier, semicolon} */
@} /* @r{close-brace} */
value of @samp{a} from the outer scope. So this approach cannot
work.
-A simple solution to this problem is to declare the parser to
+A simple solution to this problem is to declare the parser to
use the @acronym{GLR} algorithm.
When the @acronym{GLR} parser reaches the critical state, it
merely splits into two branches and pursues both syntax rules
The parser can be turned into a @acronym{GLR} parser, while also telling Bison
to be silent about the one known reduce/reduce conflict, by
-adding these two declarations to the Bison input file (before the first
+adding these two declarations to the Bison input file (before the first
@samp{%%}):
@example
intended. A @acronym{GLR} parser splitting inadvertently may cause
problems less obvious than an @acronym{LALR} parser statically choosing the
wrong alternative in a conflict.
-Second, consider interactions with the lexer (@pxref{Semantic Tokens})
+Second, consider interactions with the lexer (@pxref{Semantic Tokens})
with great care. Since a split parser consumes tokens
without performing any actions during the split, the lexer cannot
obtain information via parser actions. Some cases of
@samp{x} as an @code{ID}).
Bison detects this as a reduce/reduce conflict between the rules
@code{expr : ID} and @code{declarator : ID}, which it cannot resolve at the
-time it encounters @code{x} in the example above. Since this is a
-@acronym{GLR} parser, it therefore splits the problem into two parses, one for
+time it encounters @code{x} in the example above. Since this is a
+@acronym{GLR} parser, it therefore splits the problem into two parses, one for
each choice of resolving the reduce/reduce conflict.
Unlike the example from the previous section (@pxref{Simple GLR Parsers}),
however, neither of these parses ``dies,'' because the grammar as it stands is
-ambiguous. One of the parsers eventually reduces @code{stmt : expr ';'} and
-the other reduces @code{stmt : decl}, after which both parsers are in an
-identical state: they've seen @samp{prog stmt} and have the same unprocessed
-input remaining. We say that these parses have @dfn{merged.}
+ambiguous. One of the parsers eventually reduces @code{stmt : expr ';'} and
+the other reduces @code{stmt : decl}, after which both parsers are in an
+identical state: they've seen @samp{prog stmt} and have the same unprocessed
+input remaining. We say that these parses have @dfn{merged.}
At this point, the @acronym{GLR} parser requires a specification in the
grammar of how to choose between the competing parses.
In the example above, the two @code{%dprec}
-declarations specify that Bison is to give precedence
+declarations specify that Bison is to give precedence
to the parse that interprets the example as a
@code{decl}, which implies that @code{x} is a declarator.
The parser therefore prints
@end example
@noindent
-This is another example of using @acronym{GLR} to parse an unambiguous
+This is another example of using @acronym{GLR} to parse an unambiguous
construct, as shown in the previous section (@pxref{Simple GLR Parsers}).
Here, there is no ambiguity (this cannot be parsed as a declaration).
However, at the time the Bison parser encounters @code{x}, it does not
@end example
Bison requires that all of the
-productions that participate in any particular merge have identical
+productions that participate in any particular merge have identical
@samp{%merge} clauses. Otherwise, the ambiguity would be unresolvable,
and the parser will report an error during any parse that results in
the offending merge.
arrange for it to call @code{yyparse} or the parser will never run.
@xref{Interface, ,Parser C-Language Interface}.
-Aside from the token type names and the symbols in the actions you
+If your code defines a C preprocessor macro @code{_} (a single
+underscore), Bison assumes that it can be used to translate
+English-language strings to the user's preferred language using a
+function-like syntax, e.g., @code{_("syntax error")}. Otherwise,
+Bison defines a no-op macro by that name that merely returns its
+argument, so strings are not translated.
+
+Aside from @code{_} and the token type names and the symbols in the actions you
write, all symbols defined in the Bison parser file itself
begin with @samp{yy} or @samp{YY}. This includes interface functions
such as the lexical analyzer function @code{yylex}, the error reporting
/* The symbol table: a chain of `struct symrec'. */
extern symrec *sym_table;
-symrec *putsym (char const *, func_t);
+symrec *putsym (char const *, int);
symrec *getsym (char const *);
@end group
@end smallexample
definitions of @code{yylex} and @code{yyerror} often go here. Because
C requires functions to be declared before being used, you often need
to declare functions like @code{yylex} and @code{yyerror} in the Prologue,
-even if you define them int he Epilogue.
+even if you define them in the Epilogue.
@xref{Interface, ,Parser C-Language Interface}.
If the last section is empty, you may omit the @samp{%%} that separates it
The @code{YYLLOC_DEFAULT} macro takes three parameters. The first one is
the location of the grouping (the result of the computation). When a
-rule is matched, the second parameter is an array holding locations of
+rule is matched, the second parameter identifies locations of
all right hand side elements of the rule being matched, and the third
parameter is the size of the rule's right hand side. When processing
-a syntax error, the second parameter is an array holding locations of
+a syntax error, the second parameter identifies locations of
the symbols that were discarded during error processing, and the third
parameter is the number of discarded symbols.
-By default, @code{YYLLOC_DEFAULT} is defined this way for simple
-@acronym{LALR}(1) parsers:
+By default, @code{YYLLOC_DEFAULT} is defined this way:
-@example
+@smallexample
@group
-# define YYLLOC_DEFAULT(Current, Rhs, N) \
- ((Current).first_line = (Rhs)[1].first_line, \
- (Current).first_column = (Rhs)[1].first_column, \
- (Current).last_line = (Rhs)[N].last_line, \
- (Current).last_column = (Rhs)[N].last_column)
+# define YYLLOC_DEFAULT(Current, Rhs, N) \
+ do \
+ if (N) \
+ @{ \
+ (Current).first_line = YYRHSLOC(Rhs, 1).first_line; \
+ (Current).first_column = YYRHSLOC(Rhs, 1).first_column; \
+ (Current).last_line = YYRHSLOC(Rhs, N).last_line; \
+ (Current).last_column = YYRHSLOC(Rhs, N).last_column; \
+ @} \
+ else \
+ @{ \
+ (Current).first_line = (Current).last_line = \
+ YYRHSLOC(Rhs, 0).last_line; \
+ (Current).first_column = (Current).last_column = \
+ YYRHSLOC(Rhs, 0).last_column; \
+ @} \
+ while (0)
@end group
-@end example
+@end smallexample
-@noindent
-and like this for @acronym{GLR} parsers:
-
-@example
-@group
-# define YYLLOC_DEFAULT(yyCurrent, yyRhs, YYN) \
- ((yyCurrent).first_line = YYRHSLOC(yyRhs, 1).first_line, \
- (yyCurrent).first_column = YYRHSLOC(yyRhs, 1).first_column, \
- (yyCurrent).last_line = YYRHSLOC(yyRhs, YYN).last_line, \
- (yyCurrent).last_column = YYRHSLOC(yyRhs, YYN).last_column)
-@end group
-@end example
+where @code{YYRHSLOC (rhs, k)} is the location of the @var{k}th symbol
+in @var{rhs} when @var{k} is positive, and the location of the symbol
+just before the reduction when @var{k} and @var{n} are both zero.
When defining @code{YYLLOC_DEFAULT}, you should consider that:
result) should be modified by @code{YYLLOC_DEFAULT}.
@item
-For consistency with semantic actions, valid indexes for the location
-array range from 1 to @var{n}.
+For consistency with semantic actions, valid indexes within the
+right hand side range from 1 to @var{n}. When @var{n} is zero, only 0 is a
+valid index, and it refers to the symbol just before the reduction.
+During error processing @var{n} is always positive.
@item
Your macro should parenthesize its arguments, if need be, since the
* Precedence Decl:: Declaring terminals with precedence and associativity.
* Union Decl:: Declaring the set of all semantic value types.
* Type Decl:: Declaring the choice of type for a nonterminal symbol.
+* Initial Action Decl:: Code run before parsing starts.
* Destructor Decl:: Declaring how symbols are freed.
* Expect Decl:: Suppressing warnings about parsing conflicts.
* Start Decl:: Specifying the start symbol.
terminal symbol. All kinds of token declarations allow
@code{<@var{type}>}.
+@node Initial Action Decl
+@subsection Performing Actions before Parsing
+@findex %initial-action
+
+Sometimes your parser needs to perform some initializations before
+parsing. The @code{%initial-action} directive allows for such arbitrary
+code.
+
+@deffn {Directive} %initial-action @{ @var{code} @}
+@findex %initial-action
+Declare that the @var{code} must be invoked before parsing each time
+@code{yyparse} is called. The @var{code} may use @code{$$} and
+@code{@@$} --- initial value and location of the look-ahead --- and the
+@code{%parse-param}.
+@end deffn
+
+For instance, if your locations use a file name, you may use
+
+@example
+%parse-param @{ const char *filename @};
+%initial-action
+@{
+ @@$.begin.filename = @@$.end.filename = filename;
+@};
+@end example
+
+
@node Destructor Decl
@subsection Freeing Discarded Symbols
@cindex freeing discarded symbols
@findex %destructor
-Some symbols can be discarded by the parser, typically during error
-recovery (@pxref{Error Recovery}). Basically, during error recovery,
-embarrassing symbols already pushed on the stack, and embarrassing
-tokens coming from the rest of the file are thrown away until the parser
-falls on its feet. If these symbols convey heap based information, this
-memory is lost. While this behavior is tolerable for batch parsers,
-such as in compilers, it is unacceptable for parsers that can
-possibility ``never end'' such as shells, or implementations of
+Some symbols can be discarded by the parser. For instance, during error
+recovery (@pxref{Error Recovery}), embarrassing symbols already pushed
+on the stack, and embarrassing tokens coming from the rest of the file
+are thrown away until the parser falls on its feet. If these symbols
+convey heap based information, this memory is lost. While this behavior
+can be tolerable for batch parsers, such as in compilers, it is not for
+possibly ``never ending'' parsers such as shells, or implementations of
communication protocols.
The @code{%destructor} directive allows for the definition of code that
typefull: string; // $$ = $1 applies, $1 is not destroyed.
@end smallexample
+@sp 1
+
+@cindex discarded symbols
+@dfn{Discarded symbols} are the following:
+
+@itemize
+@item
+stacked symbols popped during the first phase of error recovery,
+@item
+incoming terminals during the second phase of error recovery,
+@item
+the current look-ahead when the parser aborts (either via an explicit
+call to @code{YYABORT}, or as a consequence of a failed error recovery).
+@end itemize
+
+
@node Expect Decl
@subsection Suppressing Conflict Warnings
@cindex suppressing conflict warnings
parser stack can become before a stack overflow occurs. Define the
macro with a value that is an integer. This value is the maximum number
of tokens that can be shifted (and not reduced) before overflow.
-It must be a constant expression whose value is known at compile time.
The stack space allowed is not necessarily allocated. If you specify a
large value for @code{YYMAXDEPTH}, the parser actually allocates a small
you do not need to make @code{YYMAXDEPTH} painfully small merely to save
space for ordinary inputs that do not need much stack.
+However, do not allow @code{YYMAXDEPTH} to be a value so large that
+arithmetic overflow could occur when calculating the size of the stack
+space. Also, do not allow @code{YYMAXDEPTH} to be less than
+@code{YYINITDEPTH}.
+
@cindex default stack limit
The default value of @code{YYMAXDEPTH}, if you do not define it, is
10000.
@vindex YYINITDEPTH
You can control how much stack is allocated initially by defining the
-macro @code{YYINITDEPTH}. This value too must be a compile-time
-constant integer. The default is 200.
+macro @code{YYINITDEPTH} to a positive integer. For the C
+@acronym{LALR}(1) parser, this value must be a compile-time constant
+unless you are assuming C99 or some other target language or compiler
+that allows variable-length arrays. The default is 200.
+
+Do not allow @code{YYINITDEPTH} to be a value so large that arithmetic
+overflow would occur when calculating the size of the stack space.
+Also, do not allow @code{YYINITDEPTH} to be greater than
+@code{YYMAXDEPTH}.
@c FIXME: C++ output.
Because of semantical differences between C and C++, the
-@acronym{LALR}(1) parsers
-in C produced by Bison by compiled as C++ cannot grow. In this precise
-case (compiling a C parser as C++) you are suggested to grow
-@code{YYINITDEPTH}. In the near future, a C++ output output will be
-provided which addresses this issue.
+@acronym{LALR}(1) parsers in C produced by Bison by compiled as C++
+cannot grow. In this precise case (compiling a C parser as C++) you are
+suggested to grow @code{YYINITDEPTH}. In the near future, a C++ output
+output will be provided which addresses this issue.
@node Error Recovery
@chapter Error Recovery
earlier:
@example
-typedef int foo, bar, lose;
-static foo (bar); /* @r{redeclare @code{bar} as static variable} */
-static int foo (lose); /* @r{redeclare @code{foo} as function} */
+typedef int foo, bar;
+int baz (void)
+@{
+ static bar (bar); /* @r{redeclare @code{bar} as static variable} */
+ extern foo foo (foo); /* @r{redeclare @code{foo} as function} */
+ return foo (bar);
+@}
@end example
Unfortunately, the name being declared is separated from the declaration
How can I generate parsers in C++?
@end display
-We are working on a C++ output for Bison, but unfortunately, for lack
-of time, the skeleton is not finished. It is functional, but in
-numerous respects, it will require additional work which @emph{might}
-break backward compatibility. Since the skeleton for C++ is not
-documented, we do not consider ourselves bound to this interface,
-nevertheless, as much as possible we will try to keep compatibility.
+We are working on a C++ output for Bison, but unfortunately, for lack of
+time, the skeleton is not finished. It is functional, but in numerous
+respects, it will require additional work which @emph{might} break
+backward compatibility. Since the skeleton for C++ is not documented,
+we do not consider ourselves bound to this interface, nevertheless, as
+much as possible we will try to keep compatibility.
-Another possibility is to use the regular C parsers, and to compile
-them with a C++ compiler. This works properly, provided that you bear
-some simple C++ rules in mind, such as not including ``real classes''
-(i.e., structure with constructors) in unions. Therefore, in the
-@code{%union}, use pointers to classes, or better yet, a single
-pointer type to the root of your lexical/syntactic hierarchy.
+Another possibility is to use the regular C parsers, and to compile them
+with a C++ compiler. This works properly, provided that you bear some
+simple C++ rules in mind, such as not including ``real classes'' (i.e.,
+structure with constructors) in unions. Therefore, in the
+@code{%union}, use pointers to classes.
@node Implementing Gotos/Loops
right-hand side of the rule. @xref{Actions}.
@end deffn
-@deffn {Symbol} $accept
-The predefined nonterminal whose only rule is @samp{$accept: @var{start}
-$end}, where @var{start} is the start symbol. @xref{Start Decl, , The
-Start-Symbol}. It cannot be used in the grammar.
-@end deffn
-
-@deffn {Symbol} $end
-The predefined token marking the end of the token stream. It cannot be
-used in the grammar.
-@end deffn
-
-@deffn {Symbol} $undefined
-The predefined token onto which all undefined values returned by
-@code{yylex} are mapped. It cannot be used in the grammar, rather, use
-@code{error}.
-@end deffn
-
-@deffn {Symbol} error
-A token name reserved for error recovery. This token may be used in
-grammar rules so as to allow the Bison parser to recognize an error in
-the grammar without halting the process. In effect, a sentence
-containing an error may be recognized as valid. On a syntax error, the
-token @code{error} becomes the current look-ahead token. Actions
-corresponding to @code{error} are then executed, and the look-ahead
-token is reset to the token that originally caused the violation.
-@xref{Error Recovery}.
-@end deffn
-
-@deffn {Macro} 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}}.
-@end deffn
-
-@deffn {Macro} YYACCEPT
-Macro to pretend that a complete utterance of the language has been
-read, by making @code{yyparse} return 0 immediately.
-@xref{Parser Function, ,The Parser Function @code{yyparse}}.
-@end deffn
-
-@deffn {Macro} YYBACKUP
-Macro to discard a value from the parser stack and fake a look-ahead
-token. @xref{Action Features, ,Special Features for Use in Actions}.
-@end deffn
-
-@deffn {Macro} YYDEBUG
-Macro to define to equip the parser with tracing code. @xref{Tracing,
-,Tracing Your Parser}.
-@end deffn
-
-@deffn {Macro} YYERROR
-Macro to pretend that a syntax error has just been detected: call
-@code{yyerror} and then perform normal error recovery if possible
-(@pxref{Error Recovery}), or (if recovery is impossible) make
-@code{yyparse} return 1. @xref{Error Recovery}.
-@end deffn
-
-@deffn {Macro} YYERROR_VERBOSE
-An obsolete macro that you define with @code{#define} in the prologue
-to request verbose, specific error message strings
-when @code{yyerror} is called. It doesn't matter what definition you
-use for @code{YYERROR_VERBOSE}, just whether you define it. Using
-@code{%error-verbose} is preferred.
-@end deffn
-
-@deffn {Macro} YYINITDEPTH
-Macro for specifying the initial size of the parser stack.
-@xref{Stack Overflow}.
-@end deffn
-
-@deffn {Macro} YYLEX_PARAM
-An obsolete macro for specifying an extra argument (or list of extra
-arguments) for @code{yyparse} to pass to @code{yylex}. he use of this
-macro is deprecated, and is supported only for Yacc like parsers.
-@xref{Pure Calling,, Calling Conventions for Pure Parsers}.
-@end deffn
-
-@deffn {Type} YYLTYPE
-Data type of @code{yylloc}; by default, a structure with four
-members. @xref{Location Type, , Data Types of Locations}.
-@end deffn
-
-@deffn {Macro} YYMAXDEPTH
-Macro for specifying the maximum size of the parser stack. @xref{Stack
-Overflow}.
-@end deffn
-
-@deffn {Macro} YYPARSE_PARAM
-An obsolete macro for specifying the name of a parameter that
-@code{yyparse} should accept. The use of this macro is deprecated, and
-is supported only for Yacc like parsers. @xref{Pure Calling,, Calling
-Conventions for Pure Parsers}.
-@end deffn
-
-@deffn {Macro} YYRECOVERING
-Macro whose value indicates whether the parser is recovering from a
-syntax error. @xref{Action Features, ,Special Features for Use in Actions}.
-@end deffn
-
-@deffn {Macro} 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.
-@end deffn
-
-@deffn {Type} YYSTYPE
-Data type of semantic values; @code{int} by default.
-@xref{Value Type, ,Data Types of Semantic Values}.
-@end deffn
-
-@deffn {Variable} 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}.
-@end deffn
-
-@deffn {Variable} yyclearin
-Macro used in error-recovery rule actions. It clears the previous
-look-ahead token. @xref{Error Recovery}.
-@end deffn
-
-@deffn {Variable} yydebug
-External integer variable set to zero by default. If @code{yydebug}
-is given a nonzero value, the parser will output information on input
-symbols and parser action. @xref{Tracing, ,Tracing Your Parser}.
-@end deffn
-
-@deffn {Macro} yyerrok
-Macro to cause parser to recover immediately to its normal mode
-after a syntax error. @xref{Error Recovery}.
+@deffn {Delimiter} %%
+Delimiter used to separate the grammar rule section from the
+Bison declarations section or the epilogue.
+@xref{Grammar Layout, ,The Overall Layout of a Bison Grammar}.
@end deffn
-@deffn {Function} yyerror
-User-supplied function to be called by @code{yyparse} on error.
-@xref{Error Reporting, ,The Error
-Reporting Function @code{yyerror}}.
+@c Don't insert spaces, or check the DVI output.
+@deffn {Delimiter} %@{@var{code}%@}
+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}.
@end deffn
-@deffn {Function} yylex
-User-supplied lexical analyzer function, called with no arguments to get
-the next token. @xref{Lexical, ,The Lexical Analyzer Function
-@code{yylex}}.
+@deffn {Construct} /*@dots{}*/
+Comment delimiters, as in C.
@end deffn
-@deffn {Variable} yylval
-External variable in which @code{yylex} should place the semantic
-value associated with a token. (In a pure parser, it is a local
-variable within @code{yyparse}, and its address is passed to
-@code{yylex}.) @xref{Token Values, ,Semantic Values of Tokens}.
+@deffn {Delimiter} :
+Separates a rule's result from its components. @xref{Rules, ,Syntax of
+Grammar Rules}.
@end deffn
-@deffn {Variable} 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
-@code{yylex}.) You can ignore this variable if you don't use the
-@samp{@@} feature in the grammar actions. @xref{Token Locations,
-,Textual Locations of Tokens}.
+@deffn {Delimiter} ;
+Terminates a rule. @xref{Rules, ,Syntax of Grammar Rules}.
@end deffn
-@deffn {Variable} yynerrs
-Global variable which Bison increments each time there is a syntax error.
-(In a pure parser, it is a local variable within @code{yyparse}.)
-@xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}.
+@deffn {Delimiter} |
+Separates alternate rules for the same result nonterminal.
+@xref{Rules, ,Syntax of Grammar Rules}.
@end deffn
-@deffn {Function} yyparse
-The parser function produced by Bison; call this function to start
-parsing. @xref{Parser Function, ,The Parser Function @code{yyparse}}.
+@deffn {Symbol} $accept
+The predefined nonterminal whose only rule is @samp{$accept: @var{start}
+$end}, where @var{start} is the start symbol. @xref{Start Decl, , The
+Start-Symbol}. It cannot be used in the grammar.
@end deffn
@deffn {Directive} %debug
@acronym{GLR} Parsers}.
@end deffn
+@deffn {Symbol} $end
+The predefined token marking the end of the token stream. It cannot be
+used in the grammar.
+@end deffn
+
+@deffn {Symbol} error
+A token name reserved for error recovery. This token may be used in
+grammar rules so as to allow the Bison parser to recognize an error in
+the grammar without halting the process. In effect, a sentence
+containing an error may be recognized as valid. On a syntax error, the
+token @code{error} becomes the current look-ahead token. Actions
+corresponding to @code{error} are then executed, and the look-ahead
+token is reset to the token that originally caused the violation.
+@xref{Error Recovery}.
+@end deffn
+
@deffn {Directive} %error-verbose
Bison declaration to request verbose, specific error message strings
when @code{yyerror} is called.
Parsers, ,Writing @acronym{GLR} Parsers}.
@end deffn
+@deffn {Directive} %initial-action
+Run user code before parsing. @xref{Initial Action Decl, , Performing Actions before Parsing}.
+@end deffn
+
@deffn {Directive} %left
Bison declaration to assign left associativity to token(s).
@xref{Precedence Decl, ,Operator Precedence}.
,Nonterminal Symbols}.
@end deffn
+@deffn {Symbol} $undefined
+The predefined token onto which all undefined values returned by
+@code{yylex} are mapped. It cannot be used in the grammar, rather, use
+@code{error}.
+@end deffn
+
@deffn {Directive} %union
Bison declaration to specify several possible data types for semantic
values. @xref{Union Decl, ,The Collection of Value Types}.
@end deffn
-@sp 1
+@deffn {Macro} 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}}.
+@end deffn
-These are the punctuation and delimiters used in Bison input:
+@deffn {Macro} YYACCEPT
+Macro to pretend that a complete utterance of the language has been
+read, by making @code{yyparse} return 0 immediately.
+@xref{Parser Function, ,The Parser Function @code{yyparse}}.
+@end deffn
-@deffn {Delimiter} %%
-Delimiter used to separate the grammar rule section from the
-Bison declarations section or the epilogue.
-@xref{Grammar Layout, ,The Overall Layout of a Bison Grammar}.
+@deffn {Macro} YYBACKUP
+Macro to discard a value from the parser stack and fake a look-ahead
+token. @xref{Action Features, ,Special Features for Use in Actions}.
@end deffn
-@c Don't insert spaces, or check the DVI output.
-@deffn {Delimiter} %@{@var{code}%@}
-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}.
+@deffn {Variable} 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}.
@end deffn
-@deffn {Construct} /*@dots{}*/
-Comment delimiters, as in C.
+@deffn {Variable} yyclearin
+Macro used in error-recovery rule actions. It clears the previous
+look-ahead token. @xref{Error Recovery}.
@end deffn
-@deffn {Delimiter} :
-Separates a rule's result from its components. @xref{Rules, ,Syntax of
-Grammar Rules}.
+@deffn {Macro} YYDEBUG
+Macro to define to equip the parser with tracing code. @xref{Tracing,
+,Tracing Your Parser}.
@end deffn
-@deffn {Delimiter} ;
-Terminates a rule. @xref{Rules, ,Syntax of Grammar Rules}.
+@deffn {Variable} yydebug
+External integer variable set to zero by default. If @code{yydebug}
+is given a nonzero value, the parser will output information on input
+symbols and parser action. @xref{Tracing, ,Tracing Your Parser}.
@end deffn
-@deffn {Delimiter} |
-Separates alternate rules for the same result nonterminal.
-@xref{Rules, ,Syntax of Grammar Rules}.
+@deffn {Macro} yyerrok
+Macro to cause parser to recover immediately to its normal mode
+after a syntax error. @xref{Error Recovery}.
+@end deffn
+
+@deffn {Macro} YYERROR
+Macro to pretend that a syntax error has just been detected: call
+@code{yyerror} and then perform normal error recovery if possible
+(@pxref{Error Recovery}), or (if recovery is impossible) make
+@code{yyparse} return 1. @xref{Error Recovery}.
+@end deffn
+
+@deffn {Function} yyerror
+User-supplied function to be called by @code{yyparse} on error.
+@xref{Error Reporting, ,The Error
+Reporting Function @code{yyerror}}.
+@end deffn
+
+@deffn {Macro} YYERROR_VERBOSE
+An obsolete macro that you define with @code{#define} in the prologue
+to request verbose, specific error message strings
+when @code{yyerror} is called. It doesn't matter what definition you
+use for @code{YYERROR_VERBOSE}, just whether you define it. Using
+@code{%error-verbose} is preferred.
+@end deffn
+
+@deffn {Macro} YYINITDEPTH
+Macro for specifying the initial size of the parser stack.
+@xref{Stack Overflow}.
+@end deffn
+
+@deffn {Function} yylex
+User-supplied lexical analyzer function, called with no arguments to get
+the next token. @xref{Lexical, ,The Lexical Analyzer Function
+@code{yylex}}.
+@end deffn
+
+@deffn {Macro} YYLEX_PARAM
+An obsolete macro for specifying an extra argument (or list of extra
+arguments) for @code{yyparse} to pass to @code{yylex}. he use of this
+macro is deprecated, and is supported only for Yacc like parsers.
+@xref{Pure Calling,, Calling Conventions for Pure Parsers}.
+@end deffn
+
+@deffn {Variable} 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
+@code{yylex}.) You can ignore this variable if you don't use the
+@samp{@@} feature in the grammar actions. @xref{Token Locations,
+,Textual Locations of Tokens}.
+@end deffn
+
+@deffn {Type} YYLTYPE
+Data type of @code{yylloc}; by default, a structure with four
+members. @xref{Location Type, , Data Types of Locations}.
+@end deffn
+
+@deffn {Variable} yylval
+External variable in which @code{yylex} should place the semantic
+value associated with a token. (In a pure parser, it is a local
+variable within @code{yyparse}, and its address is passed to
+@code{yylex}.) @xref{Token Values, ,Semantic Values of Tokens}.
+@end deffn
+
+@deffn {Macro} YYMAXDEPTH
+Macro for specifying the maximum size of the parser stack. @xref{Stack
+Overflow}.
+@end deffn
+
+@deffn {Variable} yynerrs
+Global variable which Bison increments each time there is a syntax error.
+(In a pure parser, it is a local variable within @code{yyparse}.)
+@xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}.
+@end deffn
+
+@deffn {Function} yyparse
+The parser function produced by Bison; call this function to start
+parsing. @xref{Parser Function, ,The Parser Function @code{yyparse}}.
+@end deffn
+
+@deffn {Macro} YYPARSE_PARAM
+An obsolete macro for specifying the name of a parameter that
+@code{yyparse} should accept. The use of this macro is deprecated, and
+is supported only for Yacc like parsers. @xref{Pure Calling,, Calling
+Conventions for Pure Parsers}.
+@end deffn
+
+@deffn {Macro} YYRECOVERING
+Macro whose value indicates whether the parser is recovering from a
+syntax error. @xref{Action Features, ,Special Features for Use in Actions}.
+@end deffn
+
+@deffn {Macro} YYSTACK_USE_ALLOCA
+Macro used to control the use of @code{alloca} when the C
+@acronym{LALR}(1) parser needs to extend its stacks. If defined to 0,
+the parser will use @code{malloc} to extend its stacks. If defined to
+1, the parser will use @code{alloca}. Values other than 0 and 1 are
+reserved for future Bison extensions. If not defined,
+@code{YYSTACK_USE_ALLOCA} defaults to 0.
+
+If you define @code{YYSTACK_USE_ALLOCA} to 1, it is your
+responsibility to make sure that @code{alloca} is visible, e.g., by
+using @acronym{GCC} or by including @code{<stdlib.h>}. Furthermore,
+in the all-too-common case where your code may run on a host with a
+limited stack and with unreliable stack-overflow checking, you should
+set @code{YYMAXDEPTH} to a value that cannot possibly result in
+unchecked stack overflow on any of your target hosts when
+@code{alloca} is called. You can inspect the code that Bison
+generates in order to determine the proper numeric values. This will
+require some expertise in low-level implementation details.
+@end deffn
+
+@deffn {Type} YYSTYPE
+Data type of semantic values; @code{int} by default.
+@xref{Value Type, ,Data Types of Semantic Values}.
@end deffn
@node Glossary
projects / bison.git / blobdiff