Various DJGGP specific issues in /djgpp.

[bison.git] / doc / bison.texinfo

diff --git a/doc/bison.texinfo b/doc/bison.texinfo
index 74e5381265e4471f92d90735720a2aecc8567d82..c004a842a73125edb6f2b7b49775b5db3d76bc10 100644 (file)
--- a/doc/bison.texinfo
+++ b/doc/bison.texinfo
@@ -44,7 +44,7 @@ This manual is for @acronym{GNU} Bison (version @value{VERSION},
 @value{UPDATED}), the @acronym{GNU} parser generator.
 
 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998,
 @value{UPDATED}), the @acronym{GNU} parser generator.
 
 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1995, 1998,

-1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.

 
 @quotation
 Permission is granted to copy, distribute and/or modify this document
 
 @quotation
 Permission is granted to copy, distribute and/or modify this document


@@ -145,9 +145,10 @@ The Concepts of Bison
 
 Writing @acronym{GLR} Parsers
 
 
 Writing @acronym{GLR} Parsers
 

-* Simple GLR Parsers::       Using @acronym{GLR} parsers on unambiguous grammars
-* Merging GLR Parses::       Using @acronym{GLR} parsers to resolve ambiguities
-* Compiler Requirements::    @acronym{GLR} parsers require a modern C compiler
+* Simple GLR Parsers::      Using @acronym{GLR} parsers on unambiguous grammars.
+* Merging GLR Parses::      Using @acronym{GLR} parsers to resolve ambiguities.
+* GLR Semantic Actions::    Deferred semantic actions have special concerns.
+* Compiler Requirements::   @acronym{GLR} parsers require a modern C compiler.

 
 Examples
 
 
 Examples
 


@@ -733,9 +734,10 @@ user-defined function on the resulting values to produce an arbitrary
 merged result.
 
 @menu
 merged result.
 
 @menu

-* Simple GLR Parsers::       Using @acronym{GLR} parsers on unambiguous grammars
-* Merging GLR Parses::       Using @acronym{GLR} parsers to resolve ambiguities
-* Compiler Requirements::    @acronym{GLR} parsers require a modern C compiler
+* Simple GLR Parsers::      Using @acronym{GLR} parsers on unambiguous grammars.
+* Merging GLR Parses::      Using @acronym{GLR} parsers to resolve ambiguities.
+* GLR Semantic Actions::    Deferred semantic actions have special concerns.
+* Compiler Requirements::   @acronym{GLR} parsers require a modern C compiler.

 @end menu
 
 @node Simple GLR Parsers
 @end menu
 
 @node Simple GLR Parsers


@@ -910,29 +912,27 @@ parser recognizes all valid declarations, according to the
 limited syntax above, transparently.  In fact, the user does not even
 notice when the parser splits.
 
 limited syntax above, transparently.  In fact, the user does not even
 notice when the parser splits.
 

-So here we have a case where we can use the benefits of @acronym{GLR}, almost
-without disadvantages.  Even in simple cases like this, however, there
-are at least two potential problems to beware.
-First, always analyze the conflicts reported by
-Bison to make sure that @acronym{GLR} splitting is only done where it is
-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})
-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
-lexer interactions can be eliminated by using @acronym{GLR} to
-shift the complications from the lexer to the parser.  You must check
-the remaining cases for correctness.
-
-In our example, it would be safe for the lexer to return tokens
-based on their current meanings in some symbol table, because no new
-symbols are defined in the middle of a type declaration.  Though it
-is possible for a parser to define the enumeration
-constants as they are parsed, before the type declaration is
-completed, it actually makes no difference since they cannot be used
-within the same enumerated type declaration.
+So here we have a case where we can use the benefits of @acronym{GLR},
+almost without disadvantages.  Even in simple cases like this, however,
+there are at least two potential problems to beware.  First, always
+analyze the conflicts reported by Bison to make sure that @acronym{GLR}
+splitting is only done where it is 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}) 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 lexer interactions can be
+eliminated by using @acronym{GLR} to shift the complications from the
+lexer to the parser.  You must check the remaining cases for
+correctness.
+
+In our example, it would be safe for the lexer to return tokens based on
+their current meanings in some symbol table, because no new symbols are
+defined in the middle of a type declaration.  Though it is possible for
+a parser to define the enumeration constants as they are parsed, before
+the type declaration is completed, it actually makes no difference since
+they cannot be used within the same enumerated type declaration.

 
 @node Merging GLR Parses
 @subsection Using @acronym{GLR} to Resolve Ambiguities
 
 @node Merging GLR Parses
 @subsection Using @acronym{GLR} to Resolve Ambiguities


@@ -1096,6 +1096,52 @@ productions that participate in any particular merge have identical
 and the parser will report an error during any parse that results in
 the offending merge.
 
 and the parser will report an error during any parse that results in
 the offending merge.
 

+@node GLR Semantic Actions
+@subsection GLR Semantic Actions
+
+@cindex deferred semantic actions
+By definition, a deferred semantic action is not performed at the same time as
+the associated reduction.
+This raises caveats for several Bison features you might use in a semantic
+action in a @acronym{GLR} parser.
+
+@vindex yychar
+@cindex @acronym{GLR} parsers and @code{yychar}
+@vindex yylval
+@cindex @acronym{GLR} parsers and @code{yylval}
+@vindex yylloc
+@cindex @acronym{GLR} parsers and @code{yylloc}
+In any semantic action, you can examine @code{yychar} to determine the type of
+the look-ahead token present at the time of the associated reduction.
+After checking that @code{yychar} is not set to @code{YYEMPTY} or @code{YYEOF},
+you can then examine @code{yylval} and @code{yylloc} to determine the
+look-ahead token's semantic value and location, if any.
+In a nondeferred semantic action, you can also modify any of these variables to
+influence syntax analysis.
+@xref{Look-Ahead, ,Look-Ahead Tokens}.
+
+@findex yyclearin
+@cindex @acronym{GLR} parsers and @code{yyclearin}
+In a deferred semantic action, it's too late to influence syntax analysis.
+In this case, @code{yychar}, @code{yylval}, and @code{yylloc} are set to
+shallow copies of the values they had at the time of the associated reduction.
+For this reason alone, modifying them is dangerous.
+Moreover, the result of modifying them is undefined and subject to change with
+future versions of Bison.
+For example, if a semantic action might be deferred, you should never write it
+to invoke @code{yyclearin} (@pxref{Action Features}) or to attempt to free
+memory referenced by @code{yylval}.
+
+@findex YYERROR
+@cindex @acronym{GLR} parsers and @code{YYERROR}
+Another Bison feature requiring special consideration is @code{YYERROR}
+(@pxref{Action Features}), which you can invoke in any semantic action to
+initiate error recovery.
+During deterministic @acronym{GLR} operation, the effect of @code{YYERROR} is
+the same as its effect in an @acronym{LALR}(1) parser.
+In a deferred semantic action, its effect is undefined.
+@c The effect is probably a syntax error at the split point.
+

 @node Compiler Requirements
 @subsection Considerations when Compiling @acronym{GLR} Parsers
 @cindex @code{inline}
 @node Compiler Requirements
 @subsection Considerations when Compiling @acronym{GLR} Parsers
 @cindex @code{inline}


@@ -2585,13 +2631,17 @@ continues until end of line.
 @cindex Prologue
 @cindex declarations
 
 @cindex Prologue
 @cindex declarations
 

-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
-@samp{#include} to get the declarations from a header file.  If you don't
-need any C declarations, you may omit the @samp{%@{} and @samp{%@}}
-delimiters that bracket this section.
+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
+@samp{#include} to get the declarations from a header file.  If you
+don't need any C declarations, you may omit the @samp{%@{} and
+@samp{%@}} delimiters that bracket this section.
+
+The @var{Prologue} section is terminated by the the first occurrence
+of @samp{%@}} that is outside a comment, a string literal, or a
+character constant.

 
 You may have more than one @var{Prologue} section, intermixed with the
 @var{Bison declarations}.  This allows you to have C and Bison
 
 You may have more than one @var{Prologue} section, intermixed with the
 @var{Bison declarations}.  This allows you to have C and Bison


@@ -2661,10 +2711,10 @@ even if you define them in the Epilogue.
 If the last section is empty, you may omit the @samp{%%} that separates it
 from the grammar rules.
 
 If the last section is empty, you may omit the @samp{%%} that separates it
 from the grammar rules.
 

-The Bison parser itself contains many macros and identifiers whose
-names start with @samp{yy} or @samp{YY}, so it is a
-good idea to avoid using any such names (except those documented in this
-manual) in the epilogue of the grammar file.
+The Bison parser itself contains many macros and identifiers whose names
+start with @samp{yy} or @samp{YY}, so it is a good idea to avoid using
+any such names (except those documented in this manual) in the epilogue
+of the grammar file.

 
 @node Symbols
 @section Symbols, Terminal and Nonterminal
 
 @node Symbols
 @section Symbols, Terminal and Nonterminal


@@ -2680,13 +2730,13 @@ A @dfn{terminal symbol} (also known as a @dfn{token type}) represents a
 class of syntactically equivalent tokens.  You use the symbol in grammar
 rules to mean that a token in that class is allowed.  The symbol is
 represented in the Bison parser by a numeric code, and the @code{yylex}
 class of syntactically equivalent tokens.  You use the symbol in grammar
 rules to mean that a token in that class is allowed.  The symbol is
 represented in the Bison parser by a numeric code, and the @code{yylex}

-function returns a token type code to indicate what kind of token has been
-read.  You don't need to know what the code value is; you can use the
-symbol to stand for it.
+function returns a token type code to indicate what kind of token has
+been read.  You don't need to know what the code value is; you can use
+the symbol to stand for it.

 
 

-A @dfn{nonterminal symbol} stands for a class of syntactically equivalent
-groupings.  The symbol name is used in writing grammar rules.  By convention,
-it should be all lower case.
+A @dfn{nonterminal symbol} stands for a class of syntactically
+equivalent groupings.  The symbol name is used in writing grammar rules.
+By convention, it should be all lower case.

 
 Symbol names can contain letters, digits (not at the beginning),
 underscores and periods.  Periods make sense only in nonterminals.
 
 Symbol names can contain letters, digits (not at the beginning),
 underscores and periods.  Periods make sense only in nonterminals.


@@ -2791,17 +2841,17 @@ characters in the following C-language string:
 "\a\b\t\n\v\f\r !\"#%&'()*+,-./:;<=>?[\\]^_@{|@}~"
 @end example
 
 "\a\b\t\n\v\f\r !\"#%&'()*+,-./:;<=>?[\\]^_@{|@}~"
 @end example
 

-The @code{yylex} function and Bison must use a consistent character
-set and encoding for character tokens.  For example, if you run Bison in an
-@acronym{ASCII} environment, but then compile and run the resulting program
-in an environment that uses an incompatible character set like
-@acronym{EBCDIC}, the resulting program may not work because the
-tables generated by Bison will assume @acronym{ASCII} numeric values for
-character tokens.  It is standard
-practice for software distributions to contain C source files that
-were generated by Bison in an @acronym{ASCII} environment, so installers on
-platforms that are incompatible with @acronym{ASCII} must rebuild those
-files before compiling them.
+The @code{yylex} function and Bison must use a consistent character set
+and encoding for character tokens.  For example, if you run Bison in an
+@acronym{ASCII} environment, but then compile and run the resulting
+program in an environment that uses an incompatible character set like
+@acronym{EBCDIC}, the resulting program may not work because the tables
+generated by Bison will assume @acronym{ASCII} numeric values for
+character tokens.  It is standard practice for software distributions to
+contain C source files that were generated by Bison in an
+@acronym{ASCII} environment, so installers on platforms that are
+incompatible with @acronym{ASCII} must rebuild those files before
+compiling them.

 
 The symbol @code{error} is a terminal symbol reserved for error recovery
 (@pxref{Error Recovery}); you shouldn't use it for any other purpose.
 
 The symbol @code{error} is a terminal symbol reserved for error recovery
 (@pxref{Error Recovery}); you shouldn't use it for any other purpose.


@@ -2853,6 +2903,22 @@ the semantics of the rule.  An action looks like this:
 @end example
 
 @noindent
 @end example
 
 @noindent

+@cindex braced code
+This is an example of @dfn{braced code}, that is, C code surrounded by
+braces, much like a compound statement in C@.  Braced code can contain
+any sequence of C tokens, so long as its braces are balanced.  Bison
+does not check the braced code for correctness directly; it merely
+copies the code to the output file, where the C compiler can check it.
+
+Within braced code, the balanced-brace count is not affected by braces
+within comments, string literals, or character constants, but it is
+affected by the C digraphs @samp{<%} and @samp{%>} that represent
+braces.  At the top level braced code must be terminated by @samp{@}}
+and not by a digraph.  Bison does not look for trigraphs, so if braced
+code uses trigraphs you should ensure that they do not affect the
+nesting of braces or the boundaries of comments, string literals, or
+character constants.
+

 Usually there is only one action and it follows the components.
 @xref{Actions}.
 
 Usually there is only one action and it follows the components.
 @xref{Actions}.
 


@@ -2908,10 +2974,10 @@ with no components.
 @section Recursive Rules
 @cindex recursive rule
 
 @section Recursive Rules
 @cindex recursive rule
 

-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 a particular thing.  Consider this recursive definition of a
+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 a particular thing.  Consider this recursive definition of a

 comma-separated sequence of one or more expressions:
 
 @example
 comma-separated sequence of one or more expressions:
 
 @example


@@ -3025,8 +3091,9 @@ This macro definition must go in the prologue of the grammar file
 
 In most programs, you will need different data types for different kinds
 of tokens and groupings.  For example, a numeric constant may need type
 
 In most programs, you will need different data types for different kinds
 of tokens and groupings.  For example, a numeric constant may need type

-@code{int} or @code{long int}, while a string constant needs type @code{char *},
-and an identifier might need a pointer to an entry in the symbol table.
+@code{int} or @code{long int}, while a string constant needs type
+@code{char *}, and an identifier might need a pointer to an entry in the
+symbol table.

 
 To use more than one data type for semantic values in one parser, Bison
 requires you to do two things:
 
 To use more than one data type for semantic values in one parser, Bison
 requires you to do two things:


@@ -3056,14 +3123,8 @@ each time an instance of that rule is recognized.  The task of most actions
 is to compute a semantic value for the grouping built by the rule from the
 semantic values associated with tokens or smaller groupings.
 
 is to compute a semantic value for the grouping built by the rule from the
 semantic values associated with tokens or smaller groupings.
 

-An action consists of C statements surrounded by braces, much like a
-compound statement in C@.  An action can contain any sequence of C
-statements.  Bison does not look for trigraphs, though, so if your C
-code uses trigraphs you should ensure that they do not affect the
-nesting of braces or the boundaries of comments, strings, or character
-literals.
-
-An action can be placed at any position in the rule;
+An action consists of braced code containing C statements, and can be
+placed at any position in the rule;

 it is executed at that position.  Most rules have just one action at the
 end of the rule, following all the components.  Actions in the middle of
 a rule are tricky and used only for special purposes (@pxref{Mid-Rule
 it is executed at that position.  Most rules have just one action at the
 end of the rule, following all the components.  Actions in the middle of
 a rule are tricky and used only for special purposes (@pxref{Mid-Rule


@@ -3141,6 +3202,12 @@ As long as @code{bar} is used only in the fashion shown here, @code{$0}
 always refers to the @code{expr} which precedes @code{bar} in the
 definition of @code{foo}.
 
 always refers to the @code{expr} which precedes @code{bar} in the
 definition of @code{foo}.
 

+@vindex yylval
+It is also possible to access the semantic value of the look-ahead token, if
+any, from a semantic action.
+This semantic value is stored in @code{yylval}.
+@xref{Action Features, ,Special Features for Use in Actions}.
+

 @node Action Types
 @subsection Data Types of Values in Actions
 @cindex action data types
 @node Action Types
 @subsection Data Types of Values in Actions
 @cindex action data types


@@ -3458,6 +3525,12 @@ exp:    @dots{}
 @end group
 @end example
 
 @end group
 @end example
 

+@vindex yylloc
+It is also possible to access the location of the look-ahead token, if any,
+from a semantic action.
+This location is stored in @code{yylloc}.
+@xref{Action Features, ,Special Features for Use in Actions}.
+

 @node Location Default Action
 @subsection Default Action for Locations
 @vindex YYLLOC_DEFAULT
 @node Location Default Action
 @subsection Default Action for Locations
 @vindex YYLLOC_DEFAULT


@@ -3709,10 +3782,10 @@ the one declared later has the higher precedence and is grouped first.
 @cindex value types, declaring
 @findex %union
 
 @cindex value types, declaring
 @findex %union
 

-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.
+The @code{%union} declaration specifies the entire collection of
+possible data types for semantic values.  The keyword @code{%union} is
+followed by braced code containing the same thing that goes inside a
+@code{union} in C@.

 
 For example:
 
 
 For example:
 


@@ -3743,10 +3816,15 @@ As an extension to @acronym{POSIX}, a tag is allowed after the
 @end group
 @end example
 
 @end group
 @end example
 

+@noindent

 specifies the union tag @code{value}, so the corresponding C type is
 @code{union value}.  If you do not specify a tag, it defaults to
 @code{YYSTYPE}.
 
 specifies the union tag @code{value}, so the corresponding C type is
 @code{union value}.  If you do not specify a tag, it defaults to
 @code{YYSTYPE}.
 

+As another extension to @acronym{POSIX}, you may specify multiple
+@code{%union} declarations; their contents are concatenated.  However,
+only the first @code{%union} declaration can specify a tag.
+

 Note that, unlike making a @code{union} declaration in C, you need not write
 a semicolon after the closing brace.
 
 Note that, unlike making a @code{union} declaration in C, you need not write
 a semicolon after the closing brace.
 


@@ -3788,7 +3866,7 @@ code.
 
 @deffn {Directive} %initial-action @{ @var{code} @}
 @findex %initial-action
 
 @deffn {Directive} %initial-action @{ @var{code} @}
 @findex %initial-action

-Declare that the @var{code} must be invoked before parsing each time
+Declare that the braced @var{code} must be invoked before parsing each time

 @code{yyparse} is called.  The @var{code} may use @code{$$} and
 @code{@@$} --- initial value and location of the look-ahead --- and the
 @code{%parse-param}.
 @code{yyparse} is called.  The @var{code} may use @code{$$} and
 @code{@@$} --- initial value and location of the look-ahead --- and the
 @code{%parse-param}.


@@ -3827,7 +3905,8 @@ symbol is automatically discarded.
 
 @deffn {Directive} %destructor @{ @var{code} @} @var{symbols}
 @findex %destructor
 
 @deffn {Directive} %destructor @{ @var{code} @} @var{symbols}
 @findex %destructor

-Invoke @var{code} whenever the parser discards one of the @var{symbols}.
+Invoke the braced @var{code} whenever the parser discards one of the
+@var{symbols}.

 Within @var{code}, @code{$$} designates the semantic value associated
 with the discarded symbol.  The additional parser parameters are also
 available (@pxref{Parser Function, , The Parser Function
 Within @var{code}, @code{$$} designates the semantic value associated
 with the discarded symbol.  The additional parser parameters are also
 available (@pxref{Parser Function, , The Parser Function


@@ -4068,13 +4147,12 @@ is named @file{@var{name}.h}.
 
 Unless @code{YYSTYPE} is already defined as a macro, the output header
 declares @code{YYSTYPE}.  Therefore, if you are using a @code{%union}
 
 Unless @code{YYSTYPE} is already defined as a macro, the output header
 declares @code{YYSTYPE}.  Therefore, if you are using a @code{%union}

-(@pxref{Multiple Types, ,More Than One Value Type}) with components
-that require other definitions, or if you have defined a
-@code{YYSTYPE} macro (@pxref{Value Type, ,Data Types of Semantic
-Values}), you need to arrange for these definitions to be propagated to
-all modules, e.g., by putting them in a
-prerequisite header that is included both by your parser and by any
-other module that needs @code{YYSTYPE}.
+(@pxref{Multiple Types, ,More Than One Value Type}) with components that
+require other definitions, or if you have defined a @code{YYSTYPE} macro
+(@pxref{Value Type, ,Data Types of Semantic Values}), you need to
+arrange for these definitions to be propagated to all modules, e.g., by
+putting them in a prerequisite header that is included both by your
+parser and by any other module that needs @code{YYSTYPE}.

 
 Unless your parser is pure, the output header declares @code{yylval}
 as an external variable.  @xref{Pure Decl, ,A Pure (Reentrant)
 
 Unless your parser is pure, the output header declares @code{yylval}
 as an external variable.  @xref{Pure Decl, ,A Pure (Reentrant)


@@ -4085,11 +4163,11 @@ If you have also used locations, the output header declares
 @code{YYSTYPE} and @code{yylval}.  @xref{Locations, ,Tracking
 Locations}.
 
 @code{YYSTYPE} and @code{yylval}.  @xref{Locations, ,Tracking
 Locations}.
 

-This output file is normally essential if you wish to put the
-definition of @code{yylex} in a separate source file, because
-@code{yylex} typically needs to be able to refer to the
-above-mentioned declarations and to the token type codes.
-@xref{Token Values, ,Semantic Values of Tokens}.
+This output file is normally essential if you wish to put the definition
+of @code{yylex} in a separate source file, because @code{yylex}
+typically needs to be able to refer to the above-mentioned declarations
+and to the token type codes.  @xref{Token Values, ,Semantic Values of
+Tokens}.

 @end deffn
 
 @deffn {Directive} %destructor
 @end deffn
 
 @deffn {Directive} %destructor


@@ -4304,8 +4382,8 @@ declaration @code{%parse-param}:
 
 @deffn {Directive} %parse-param @{@var{argument-declaration}@}
 @findex %parse-param
 
 @deffn {Directive} %parse-param @{@var{argument-declaration}@}
 @findex %parse-param

-Declare that an argument declared by @code{argument-declaration} is an
-additional @code{yyparse} argument.
+Declare that an argument declared by the braced-code
+@var{argument-declaration} is an additional @code{yyparse} argument.

 The @var{argument-declaration} is used when declaring
 functions or prototypes.  The last identifier in
 @var{argument-declaration} must be the argument name.
 The @var{argument-declaration} is used when declaring
 functions or prototypes.  The last identifier in
 @var{argument-declaration} must be the argument name.


@@ -4500,12 +4578,11 @@ then the code in @code{yylex} might look like this:
 
 @vindex yylloc
 If you are using the @samp{@@@var{n}}-feature (@pxref{Locations, ,
 
 @vindex yylloc
 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.
+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
 
 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


@@ -4550,8 +4627,8 @@ Function}).
 
 @deffn {Directive} lex-param @{@var{argument-declaration}@}
 @findex %lex-param
 
 @deffn {Directive} lex-param @{@var{argument-declaration}@}
 @findex %lex-param

-Declare that @code{argument-declaration} is an additional @code{yylex}
-argument declaration.
+Declare that the braced-code @var{argument-declaration} is an
+additional @code{yylex} argument declaration.

 @end deffn
 
 For instance:
 @end deffn
 
 For instance:


@@ -4766,6 +4843,12 @@ In either case, the rest of the action is not executed.
 Value stored in @code{yychar} when there is no look-ahead token.
 @end deffn
 
 Value stored in @code{yychar} when there is no look-ahead token.
 @end deffn
 

+@deffn {Macro} YYEOF
+@vindex YYEOF
+Value stored in @code{yychar} when the look-ahead is the end of the input
+stream.
+@end deffn
+

 @deffn {Macro} YYERROR;
 @findex YYERROR
 Cause an immediate syntax error.  This statement initiates error
 @deffn {Macro} YYERROR;
 @findex YYERROR
 Cause an immediate syntax error.  This statement initiates error


@@ -4782,15 +4865,20 @@ is recovering from a syntax error, and 0 the rest of the time.
 @end deffn
 
 @deffn {Variable} yychar
 @end deffn
 
 @deffn {Variable} yychar

-Variable containing the current look-ahead token.  (In a pure parser,
-this is actually a local variable within @code{yyparse}.)  When there is
-no look-ahead token, the value @code{YYEMPTY} is stored in the variable.
+Variable containing either the look-ahead token, or @code{YYEOF} when the
+look-ahead is the end of the input stream, or @code{YYEMPTY} when no look-ahead
+has been performed so the next token is not yet known.
+Do not modify @code{yychar} in a deferred semantic action (@pxref{GLR Semantic
+Actions}).

 @xref{Look-Ahead, ,Look-Ahead Tokens}.
 @end deffn
 
 @deffn {Macro} yyclearin;
 Discard the current look-ahead token.  This is useful primarily in
 @xref{Look-Ahead, ,Look-Ahead Tokens}.
 @end deffn
 
 @deffn {Macro} yyclearin;
 Discard the current look-ahead token.  This is useful primarily in

-error rules.  @xref{Error Recovery}.
+error rules.
+Do not invoke @code{yyclearin} in a deferred semantic action (@pxref{GLR
+Semantic Actions}).
+@xref{Error Recovery}.

 @end deffn
 
 @deffn {Macro} yyerrok;
 @end deffn
 
 @deffn {Macro} yyerrok;


@@ -4799,6 +4887,22 @@ errors.  This is useful primarily in error rules.
 @xref{Error Recovery}.
 @end deffn
 
 @xref{Error Recovery}.
 @end deffn
 

+@deffn {Variable} yylloc
+Variable containing the look-ahead token location when @code{yychar} is not set
+to @code{YYEMPTY} or @code{YYEOF}.
+Do not modify @code{yylloc} in a deferred semantic action (@pxref{GLR Semantic
+Actions}).
+@xref{Actions and Locations, ,Actions and Locations}.
+@end deffn
+
+@deffn {Variable} yylval
+Variable containing the look-ahead token semantic value when @code{yychar} is
+not set to @code{YYEMPTY} or @code{YYEOF}.
+Do not modify @code{yylval} in a deferred semantic action (@pxref{GLR Semantic
+Actions}).
+@xref{Actions, ,Actions}.
+@end deffn
+

 @deffn {Value} @@$
 @findex @@$
 Acts like a structure variable containing information on the textual location
 @deffn {Value} @@$
 @findex @@$
 Acts like a structure variable containing information on the textual location


@@ -4842,12 +4946,11 @@ Tracking Locations}.
 
 A Bison-generated parser can print diagnostics, including error and
 tracing messages.  By default, they appear in English.  However, Bison
 
 A Bison-generated parser can print diagnostics, including error and
 tracing messages.  By default, they appear in English.  However, Bison

-also supports outputting diagnostics in the user's native language.
-To make this work, the user should set the usual environment
-variables.  @xref{Users, , The User's View, gettext, GNU
-@code{gettext} utilities}.  For
-example, the shell command @samp{export LC_ALL=fr_CA.UTF-8} might set
-the user's locale to French Canadian using the @acronym{UTF}-8
+also supports outputting diagnostics in the user's native language.  To
+make this work, the user should set the usual environment variables.
+@xref{Users, , The User's View, gettext, GNU @code{gettext} utilities}.
+For example, the shell command @samp{export LC_ALL=fr_CA.UTF-8} might
+set the user's locale to French Canadian using the @acronym{UTF}-8

 encoding.  The exact set of available locales depends on the user's
 installation.
 
 encoding.  The exact set of available locales depends on the user's
 installation.
 


@@ -5037,7 +5140,11 @@ doing so would produce on the stack the sequence of symbols @code{expr
 '!'}.  No rule allows that sequence.
 
 @vindex yychar
 '!'}.  No rule allows that sequence.
 
 @vindex yychar

-The current look-ahead token is stored in the variable @code{yychar}.
+@vindex yylval
+@vindex yylloc
+The look-ahead token is stored in the variable @code{yychar}.
+Its semantic value and location, if any, are stored in the variables
+@code{yylval} and @code{yylloc}.

 @xref{Action Features, ,Special Features for Use in Actions}.
 
 @node Shift/Reduce
 @xref{Action Features, ,Special Features for Use in Actions}.
 
 @node Shift/Reduce


@@ -5854,6 +5961,7 @@ The previous look-ahead token is reanalyzed immediately after an error.  If
 this is unacceptable, then the macro @code{yyclearin} may be used to clear
 this token.  Write the statement @samp{yyclearin;} in the error rule's
 action.
 this is unacceptable, then the macro @code{yyclearin} may be used to clear
 this token.  Write the statement @samp{yyclearin;} in the error rule's
 action.

+@xref{Action Features, ,Special Features for Use in Actions}.

 
 For example, suppose that on a syntax error, an error handling routine is
 called that advances the input stream to some point where parsing should
 
 For example, suppose that on a syntax error, an error handling routine is
 called that advances the input stream to some point where parsing should


@@ -6681,13 +6789,14 @@ Print the version number of Bison and exit.
 @item --print-localedir
 Print the name of the directory containing locale-dependent data.
 
 @item --print-localedir
 Print the name of the directory containing locale-dependent data.
 

-@need 1750

 @item -y
 @itemx --yacc
 @item -y
 @itemx --yacc

-Equivalent to @samp{-o y.tab.c}; the parser output file is called
+Act more like the traditional Yacc command.  This can cause
+different diagnostics to be generated, and may change behavior in
+other minor ways.  Most importantly, imitate Yacc's output
+file name conventions, so that the parser output file is called

 @file{y.tab.c}, and the other outputs are called @file{y.output} and
 @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
+@file{y.tab.h}.  Thus, the following shell script can substitute

 for Yacc, and the Bison distribution contains such a script for
 compatibility with @acronym{POSIX}:
 
 for Yacc, and the Bison distribution contains such a script for
 compatibility with @acronym{POSIX}:
 


@@ -6695,6 +6804,12 @@ compatibility with @acronym{POSIX}:
 #! /bin/sh
 bison -y "$@@"
 @end example
 #! /bin/sh
 bison -y "$@@"
 @end example

+
+The @option{-y}/@option{--yacc} option is intended for use with
+traditional Yacc grammars.  If your grammar uses a Bison extension
+like @samp{%glr-parser}, Bison might not be Yacc-compatible even if
+this option is specified.
+

 @end table
 
 @noindent
 @end table
 
 @noindent


@@ -6774,8 +6889,6 @@ Implies @code{state} and augments the description of the automaton with
 the full set of items for each state, instead of its core only.
 @end table
 
 the full set of items for each state, instead of its core only.
 @end table
 

-For instance, on the following grammar
-

 @item -v
 @itemx --verbose
 Pretend that @code{%verbose} was specified, i.e, write an extra output
 @item -v
 @itemx --verbose
 Pretend that @code{%verbose} was specified, i.e, write an extra output


@@ -7395,6 +7508,7 @@ avoid name clashes.
 To enable memory deallocation during error recovery, use
 @code{%destructor}.
 
 To enable memory deallocation during error recovery, use
 @code{%destructor}.
 

+@c FIXME: Document %printer, and mention that it takes a braced-code operand.

 @comment file: calc++-parser.yy
 @example
 %printer    @{ debug_stream () << *$$; @} "identifier"
 @comment file: calc++-parser.yy
 @example
 %printer    @{ debug_stream () << *$$; @} "identifier"


@@ -8036,7 +8150,7 @@ token.  @xref{Action Features, ,Special Features for Use in Actions}.
 @end deffn
 
 @deffn {Variable} yychar
 @end deffn
 
 @deffn {Variable} yychar

-External integer variable that contains the integer value of the current
+External integer variable that contains the integer value of the

 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}.
 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}.


@@ -8097,7 +8211,7 @@ the next token.  @xref{Lexical, ,The Lexical Analyzer Function
 
 @deffn {Macro} YYLEX_PARAM
 An obsolete macro for specifying an extra argument (or list of extra
 
 @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
+arguments) for @code{yyparse} to pass to @code{yylex}.  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
 macro is deprecated, and is supported only for Yacc like parsers.
 @xref{Pure Calling,, Calling Conventions for Pure Parsers}.
 @end deffn


@@ -8106,9 +8220,12 @@ macro is deprecated, and is supported only for Yacc like parsers.
 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 Locations,
-,Textual Locations of Tokens}.
+@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}.
+In semantic actions, it stores the location of the look-ahead token.
+@xref{Actions and Locations, ,Actions and Locations}.

 @end deffn
 
 @deffn {Type} YYLTYPE
 @end deffn
 
 @deffn {Type} YYLTYPE


@@ -8120,7 +8237,10 @@ members.  @xref{Location Type, , Data Types of Locations}.
 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
 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}.
+@code{yylex}.)
+@xref{Token Values, ,Semantic Values of Tokens}.
+In semantic actions, it stores the semantic value of the look-ahead token.
+@xref{Actions, ,Actions}.

 @end deffn
 
 @deffn {Macro} YYMAXDEPTH
 @end deffn
 
 @deffn {Macro} YYMAXDEPTH


@@ -8381,7 +8501,7 @@ grammatically indivisible.  The piece of text it represents is a token.
 @c LocalWords: yychar yydebug msg YYNTOKENS YYNNTS YYNRULES YYNSTATES
 @c LocalWords: cparse clex deftypefun NE defmac YYACCEPT YYABORT param
 @c LocalWords: strncmp intval tindex lvalp locp llocp typealt YYBACKUP
 @c LocalWords: yychar yydebug msg YYNTOKENS YYNNTS YYNRULES YYNSTATES
 @c LocalWords: cparse clex deftypefun NE defmac YYACCEPT YYABORT param
 @c LocalWords: strncmp intval tindex lvalp locp llocp typealt YYBACKUP

-@c LocalWords: YYEMPTY YYRECOVERING yyclearin GE def UMINUS maybeword
+@c LocalWords: YYEMPTY YYEOF YYRECOVERING yyclearin GE def UMINUS maybeword

 @c LocalWords: Johnstone Shamsa Sadaf Hussain Tomita TR uref YYMAXDEPTH
 @c LocalWords: YYINITDEPTH stmnts ref stmnt initdcl maybeasm VCG notype
 @c LocalWords: hexflag STR exdent itemset asis DYYDEBUG YYFPRINTF args
 @c LocalWords: Johnstone Shamsa Sadaf Hussain Tomita TR uref YYMAXDEPTH
 @c LocalWords: YYINITDEPTH stmnts ref stmnt initdcl maybeasm VCG notype
 @c LocalWords: hexflag STR exdent itemset asis DYYDEBUG YYFPRINTF args