X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/4b3847c3c0e161b85267d077adb256a880c0f3e3..9bf1eca7c9e24c94f5a7b336ed7cc041586cb905:/doc/bison.texi diff --git a/doc/bison.texi b/doc/bison.texi index fbe780cd..8f98aa5e 100644 --- a/doc/bison.texi +++ b/doc/bison.texi @@ -110,7 +110,7 @@ Reference sections: * Glossary:: Basic concepts are explained. * Copying This Manual:: License for copying this manual. * Bibliography:: Publications cited in this manual. -* Index:: Cross-references to the text. +* Index of Terms:: Cross-references to the text. @detailmenu --- The Detailed Node Listing --- @@ -294,6 +294,7 @@ Handling Context Dependencies Debugging Your Parser * Understanding:: Understanding the structure of your parser. +* Graphviz:: Getting a visual representation of the parser. * Tracing:: Tracing the execution of your parser. Tracing Your Parser @@ -327,6 +328,7 @@ C++ Location Values * C++ position:: One point in the source file * C++ location:: Two points in the source file +* User Defined Location Type:: Required interface for locations A Complete C++ Example @@ -4552,9 +4554,9 @@ code. @deffn {Directive} %initial-action @{ @var{code} @} @findex %initial-action Declare that the braced @var{code} must be invoked before parsing each time -@code{yyparse} is called. The @var{code} may use @code{$$} and -@code{@@$} --- initial value and location of the lookahead --- and the -@code{%parse-param}. +@code{yyparse} is called. The @var{code} may use @code{$$} (or +@code{$<@var{tag}>$}) and @code{@@$} --- initial value and location of the +lookahead --- and the @code{%parse-param}. @end deffn For instance, if your locations use a file name, you may use @@ -4592,11 +4594,11 @@ symbol is automatically discarded. @deffn {Directive} %destructor @{ @var{code} @} @var{symbols} @findex %destructor Invoke the braced @var{code} whenever the parser discards one of the -@var{symbols}. -Within @var{code}, @code{$$} designates the semantic value associated -with the discarded symbol, and @code{@@$} designates its location. -The additional parser parameters are also available (@pxref{Parser Function, , -The Parser Function @code{yyparse}}). +@var{symbols}. Within @var{code}, @code{$$} (or @code{$<@var{tag}>$}) +designates the semantic value associated with the discarded symbol, and +@code{@@$} designates its location. The additional parser parameters are +also available (@pxref{Parser Function, , The Parser Function +@code{yyparse}}). When a symbol is listed among @var{symbols}, its @code{%destructor} is called a per-symbol @code{%destructor}. @@ -4701,6 +4703,10 @@ incoming terminals during the second phase of error recovery, the current lookahead and the entire stack (except the current right-hand side symbols) when the parser returns immediately, and @item +the current lookahead and the entire stack (including the current right-hand +side symbols) when the C++ parser (@file{lalr1.cc}) catches an exception in +@code{parse}, +@item the start symbol, when the parser succeeds. @end itemize @@ -4734,10 +4740,11 @@ Decl, , Freeing Discarded Symbols}). @c This is the same text as for %destructor. Invoke the braced @var{code} whenever the parser displays one of the @var{symbols}. Within @var{code}, @code{yyoutput} denotes the output stream -(a @code{FILE*} in C, and an @code{std::ostream&} in C++), -@code{$$} designates the semantic value associated with the symbol, and -@code{@@$} its location. The additional parser parameters are also -available (@pxref{Parser Function, , The Parser Function @code{yyparse}}). +(a @code{FILE*} in C, and an @code{std::ostream&} in C++), @code{$$} (or +@code{$<@var{tag}>$}) designates the semantic value associated with the +symbol, and @code{@@$} its location. The additional parser parameters are +also available (@pxref{Parser Function, , The Parser Function +@code{yyparse}}). The @var{symbols} are defined as for @code{%destructor} (@pxref{Destructor Decl, , Freeing Discarded Symbols}.): they can be per-type (e.g., @@ -5074,9 +5081,11 @@ default location or at the location specified by @var{qualifier}. @end deffn @deffn {Directive} %debug -In the parser implementation file, define the macro @code{YYDEBUG} to -1 if it is not already defined, so that the debugging facilities are -compiled. @xref{Tracing, ,Tracing Your Parser}. +In the parser implementation file, define the macro @code{YYDEBUG} (or +@code{@var{prefix}DEBUG} with @samp{%define api.prefix @var{prefix}}, see +@ref{Multiple Parsers, ,Multiple Parsers in the Same Program}) to 1 if it is +not already defined, so that the debugging facilities are compiled. +@xref{Tracing, ,Tracing Your Parser}. @end deffn @deffn {Directive} %define @var{variable} @@ -5121,6 +5130,23 @@ Values, ,Semantic Values of Tokens}. If you have declared @code{%code requires} or @code{%code provides}, the output header also contains their code. @xref{%code Summary}. + +@cindex Header guard +The generated header is protected against multiple inclusions with a C +preprocessor guard: @samp{YY_@var{PREFIX}_@var{FILE}_INCLUDED}, where +@var{PREFIX} and @var{FILE} are the prefix (@pxref{Multiple Parsers, +,Multiple Parsers in the Same Program}) and generated file name turned +uppercase, with each series of non alphanumerical characters converted to a +single underscore. + +For instance with @samp{%define api.prefix "calc"} and @samp{%defines +"lib/parse.h"}, the header will be guarded as follows. +@example +#ifndef YY_CALC_LIB_PARSE_H_INCLUDED +# define YY_CALC_LIB_PARSE_H_INCLUDED +... +#endif /* ! YY_CALC_LIB_PARSE_H_INCLUDED */ +@end example @end deffn @deffn {Directive} %defines @var{defines-file} @@ -5301,6 +5327,23 @@ Unaccepted @var{variable}s produce an error. Some of the accepted @var{variable}s are: @itemize @bullet +@c ================================================== api.location.type +@item @code{api.location.type} +@findex %define api.location.type + +@itemize @bullet +@item Language(s): C++, Java + +@item Purpose: Define the location type. +@xref{User Defined Location Type}. + +@item Accepted Values: String + +@item Default Value: none + +@item History: introduced in Bison 2.7 +@end itemize + @c ================================================== api.prefix @item @code{api.prefix} @findex %define api.prefix @@ -5308,12 +5351,14 @@ Some of the accepted @var{variable}s are: @itemize @bullet @item Language(s): All -@item Purpose: Rename exported symbols +@item Purpose: Rename exported symbols. @xref{Multiple Parsers, ,Multiple Parsers in the Same Program}. @item Accepted Values: String @item Default Value: @code{yy} + +@item History: introduced in Bison 2.6 @end itemize @c ================================================== api.pure @@ -5596,20 +5641,22 @@ also need to avoid conflicts on types and macros (e.g., @code{YYSTYPE}) exported in the generated header. The easy way to do this is to define the @code{%define} variable -@code{api.prefix} (possibly using the option -@samp{-Dapi.prefix=@var{prefix}}, see @ref{Invocation, ,Invoking Bison}). -This renames the interface functions and variables of the Bison parser to -start with @var{prefix} instead of @samp{yy}, and all the macros to start by -@var{PREFIX} (i.e., @var{prefix} upper cased) instead of @samp{YY}. You can -use this to give each parser distinct names that do not conflict. +@code{api.prefix}. With different @code{api.prefix}s it is guaranteed that +headers do not conflict when included together, and that compiled objects +can be linked together too. Specifying @samp{%define api.prefix +@var{prefix}} (or passing the option @samp{-Dapi.prefix=@var{prefix}}, see +@ref{Invocation, ,Invoking Bison}) renames the interface functions and +variables of the Bison parser to start with @var{prefix} instead of +@samp{yy}, and all the macros to start by @var{PREFIX} (i.e., @var{prefix} +upper-cased) instead of @samp{YY}. The renamed symbols include @code{yyparse}, @code{yylex}, @code{yyerror}, @code{yynerrs}, @code{yylval}, @code{yylloc}, @code{yychar} and @code{yydebug}. If you use a push parser, @code{yypush_parse}, @code{yypull_parse}, @code{yypstate}, @code{yypstate_new} and @code{yypstate_delete} will also be renamed. The renamed macros include -@code{YYSTYPE}, @code{YYSTYPE_IS_TRIVIAL}, @code{YYSTYPE_IS_DECLARED}, -@code{YYLTYPE}, @code{YYLTYPE_IS_TRIVIAL}, and @code{YYLTYPE_IS_DECLARED}. +@code{YYSTYPE}, @code{YYLTYPE}, and @code{YYDEBUG}, which is treated +specifically --- more about this below. For example, if you use @samp{%define api.prefix c}, the names become @code{cparse}, @code{clex}, @dots{}, @code{CSTYPE}, @code{CLTYPE}, and so @@ -5641,9 +5688,33 @@ extern CSTYPE clval; int cparse (void); @end example -Previously, a similar feature was provided by the obsoleted directive -@code{%name-prefix} (@pxref{Table of Symbols, ,Bison Symbols}) and option -@code{--name-prefix} (@pxref{Bison Options}). +The macro @code{YYDEBUG} is commonly used to enable the tracing support in +parsers. To comply with this tradition, when @code{api.prefix} is used, +@code{YYDEBUG} (not renamed) is used as a default value: + +@example +/* Enabling traces. */ +#ifndef CDEBUG +# if defined YYDEBUG +# if YYDEBUG +# define CDEBUG 1 +# else +# define CDEBUG 0 +# endif +# else +# define CDEBUG 0 +# endif +#endif +#if CDEBUG +extern int cdebug; +#endif +@end example + +@sp 2 + +Prior to Bison 2.6, a feature similar to @code{api.prefix} was provided by +the obsolete directive @code{%name-prefix} (@pxref{Table of Symbols, ,Bison +Symbols}) and the option @code{--name-prefix} (@pxref{Bison Options}). @node Interface @chapter Parser C-Language Interface @@ -5760,9 +5831,9 @@ function is available if either the @code{%define api.push-pull push} or @xref{Push Decl, ,A Push Parser}. @deftypefun int yypush_parse (yypstate *yyps) -The value returned by @code{yypush_parse} is the same as for yyparse with the -following exception. @code{yypush_parse} will return YYPUSH_MORE if more input -is required to finish parsing the grammar. +The value returned by @code{yypush_parse} is the same as for yyparse with +the following exception: it returns @code{YYPUSH_MORE} if more input is +required to finish parsing the grammar. @end deftypefun @node Pull Parser Function @@ -8023,6 +8094,7 @@ automaton, and how to enable and understand the parser run-time traces. @menu * Understanding:: Understanding the structure of your parser. +* Graphviz:: Getting a visual representation of the parser. * Tracing:: Tracing the execution of your parser. @end menu @@ -8439,6 +8511,114 @@ precedence of @samp{/} with respect to @samp{+}, @samp{-}, and @samp{*}, but also because the associativity of @samp{/} is not specified. +@c ================================================= Graphical Representation + +@node Graphviz +@section Visualizing Your Parser +@cindex dot + +As another means to gain better understanding of the shift/reduce +automaton corresponding to the Bison parser, a DOT file can be generated. Note +that debugging a real grammar with this is tedious at best, and impractical +most of the times, because the generated files are huge (the generation of +a PDF or PNG file from it will take very long, and more often than not it will +fail due to memory exhaustion). This option was rather designed for beginners, +to help them understand LR parsers. + +This file is generated when the @option{--graph} option is specified (see +@pxref{Invocation, , Invoking Bison}). Its name is made by removing +@samp{.tab.c} or @samp{.c} from the parser implementation file name, and +adding @samp{.dot} instead. If the grammar file is @file{foo.y}, the +Graphviz output file is called @file{foo.dot}. + +The following grammar file, @file{rr.y}, will be used in the sequel: + +@example +%% +@group +exp: a ";" | b "."; +a: "0"; +b: "0"; +@end group +@end example + +The graphical output is very similar to the textual one, and as such it is +easier understood by making direct comparisons between them. See +@ref{Debugging, , Debugging Your Parser} for a detailled analysis of the +textual report. + +@subheading Graphical Representation of States + +The items (pointed rules) for each state are grouped together in graph nodes. +Their numbering is the same as in the verbose file. See the following points, +about transitions, for examples + +When invoked with @option{--report=lookaheads}, the lookahead tokens, when +needed, are shown next to the relevant rule between square brackets as a +comma separated list. This is the case in the figure for the representation of +reductions, below. + +@sp 1 + +The transitions are represented as directed edges between the current and +the target states. + +@subheading Graphical Representation of Shifts + +Shifts are shown as solid arrows, labelled with the lookahead token for that +shift. The following describes a reduction in the @file{rr.output} file: + +@example +@group +state 3 + + 1 exp: a . ";" + + ";" shift, and go to state 6 +@end group +@end example + +A Graphviz rendering of this portion of the graph could be: + +@center @image{figs/example-shift, 100pt} + +@subheading Graphical Representation of Reductions + +Reductions are shown as solid arrows, leading to a diamond-shaped node +bearing the number of the reduction rule. The arrow is labelled with the +appropriate comma separated lookahead tokens. If the reduction is the default +action for the given state, there is no such label. + +This is how reductions are represented in the verbose file @file{rr.output}: +@example +state 1 + + 3 a: "0" . [";"] + 4 b: "0" . ["."] + + "." reduce using rule 4 (b) + $default reduce using rule 3 (a) +@end example + +A Graphviz rendering of this portion of the graph could be: + +@center @image{figs/example-reduce, 120pt} + +When unresolved conflicts are present, because in deterministic parsing +a single decision can be made, Bison can arbitrarily choose to disable a +reduction, see @ref{Shift/Reduce, , Shift/Reduce Conflicts}. Discarded actions +are distinguished by a red filling color on these nodes, just like how they are +reported between square brackets in the verbose file. + +The reduction corresponding to the rule number 0 is the acceptation state. It +is shown as a blue diamond, labelled "Acc". + +@subheading Graphical representation of go tos + +The @samp{go to} jump transitions are represented as dotted lines bearing +the name of the rule being jumped to. + +@c ================================================= Tracing @node Tracing @section Tracing Your Parser @@ -8468,18 +8648,24 @@ parser. This is compliant with POSIX Yacc. You could use YYDEBUG 1} in the prologue of the grammar file (@pxref{Prologue, , The Prologue}). -@item the option @option{-t}, @option{--debug} -Use the @samp{-t} option when you run Bison (@pxref{Invocation, -,Invoking Bison}). This is POSIX compliant too. +If the @code{%define} variable @code{api.prefix} is used (@pxref{Multiple +Parsers, ,Multiple Parsers in the Same Program}), for instance @samp{%define +api.prefix x}, then if @code{CDEBUG} is defined, its value controls the +tracing feature (enabled if and only if nonzero); otherwise tracing is +enabled if and only if @code{YYDEBUG} is nonzero. + +@item the option @option{-t} (POSIX Yacc compliant) +@itemx the option @option{--debug} (Bison extension) +Use the @samp{-t} option when you run Bison (@pxref{Invocation, ,Invoking +Bison}). With @samp{%define api.prefix c}, it defines @code{CDEBUG} to 1, +otherwise it defines @code{YYDEBUG} to 1. @item the directive @samp{%debug} @findex %debug -Add the @code{%debug} directive (@pxref{Decl Summary, ,Bison -Declaration Summary}). This is a Bison extension, which will prove -useful when Bison will output parsers for languages that don't use a -preprocessor. Unless POSIX and Yacc portability matter to -you, this is -the preferred solution. +Add the @code{%debug} directive (@pxref{Decl Summary, ,Bison Declaration +Summary}). This is a Bison extension, especially useful for languages that +don't use a preprocessor. Unless POSIX and Yacc portability matter to you, +this is the preferred solution. @end table We suggest that you always enable the debug option so that debugging is @@ -9018,13 +9204,23 @@ separated list of @var{things} among: Description of the grammar, conflicts (resolved and unresolved), and parser's automaton. +@item itemset +Implies @code{state} and augments the description of the automaton with +the full set of items for each state, instead of its core only. + @item lookahead Implies @code{state} and augments the description of the automaton with each rule's lookahead set. -@item itemset -Implies @code{state} and augments the description of the automaton with -the full set of items for each state, instead of its core only. +@item solved +Implies @code{state}. Explain how conflicts were solved thanks to +precedence and associativity directives. + +@item all +Enable all the items. + +@item none +Do not generate the report. @end table @item --report-file=@var{file} @@ -9142,8 +9338,9 @@ generated in the following files: @table @file @item position.hh @itemx location.hh -The definition of the classes @code{position} and @code{location}, -used for location tracking. @xref{C++ Location Values}. +The definition of the classes @code{position} and @code{location}, used for +location tracking. These files are not generated if the @code{%define} +variable @code{api.location.type} is defined. @xref{C++ Location Values}. @item stack.hh An auxiliary class @code{stack} used by the parser. @@ -9199,18 +9396,22 @@ Symbols}. @c - %define filename_type "const symbol::Symbol" When the directive @code{%locations} is used, the C++ parser supports -location tracking, see @ref{Tracking Locations}. Two auxiliary classes -define a @code{position}, a single point in a file, and a @code{location}, a -range composed of a pair of @code{position}s (possibly spanning several -files). +location tracking, see @ref{Tracking Locations}. + +By default, two auxiliary classes define a @code{position}, a single point +in a file, and a @code{location}, a range composed of a pair of +@code{position}s (possibly spanning several files). But if the +@code{%define} variable @code{api.location.type} is defined, then these +classes will not be generated, and the user defined type will be used. @tindex uint In this section @code{uint} is an abbreviation for @code{unsigned int}: in genuine code only the latter is used. @menu -* C++ position:: One point in the source file -* C++ location:: Two points in the source file +* C++ position:: One point in the source file +* C++ location:: Two points in the source file +* User Defined Location Type:: Required interface for locations @end menu @node C++ position @@ -9314,6 +9515,63 @@ Report @var{p} on @var{o}, taking care of special cases such as: no @code{filename} defined, or equal filename/line or column. @end deftypefun +@node User Defined Location Type +@subsubsection User Defined Location Type +@findex %define api.location.type + +Instead of using the built-in types you may use the @code{%define} variable +@code{api.location.type} to specify your own type: + +@example +%define api.location.type @var{LocationType} +@end example + +The requirements over your @var{LocationType} are: +@itemize +@item +it must be copyable; + +@item +in order to compute the (default) value of @code{@@$} in a reduction, the +parser basically runs +@example +@@$.begin = @@$1.begin; +@@$.end = @@$@var{N}.end; // The location of last right-hand side symbol. +@end example +@noindent +so there must be copyable @code{begin} and @code{end} members; + +@item +alternatively you may redefine the computation of the default location, in +which case these members are not required (@pxref{Location Default Action}); + +@item +if traces are enabled, then there must exist an @samp{std::ostream& + operator<< (std::ostream& o, const @var{LocationType}& s)} function. +@end itemize + +@sp 1 + +In programs with several C++ parsers, you may also use the @code{%define} +variable @code{api.location.type} to share a common set of built-in +definitions for @code{position} and @code{location}. For instance, one +parser @file{master/parser.yy} might use: + +@example +%defines +%locations +%define namespace "master::" +@end example + +@noindent +to generate the @file{master/position.hh} and @file{master/location.hh} +files, reused by other parsers as follows: + +@example +%define api.location.type "master::location" +%code requires @{ #include @} +@end example + @node C++ Parser Interface @subsection C++ Parser Interface @c - define parser_class_name @@ -9351,6 +9609,11 @@ Build a new parser object. There are no arguments by default, unless @deftypemethod {parser} {int} parse () Run the syntactic analysis, and return 0 on success, 1 otherwise. + +@cindex exceptions +The whole function is wrapped in a @code{try}/@code{catch} block, so that +when an exception is thrown, the @code{%destructor}s are called to release +the lookahead symbol, and the symbols pushed on the stack. @end deftypemethod @deftypemethod {parser} {std::ostream&} debug_stream () @@ -10022,11 +10285,11 @@ class defines a @dfn{position}, a single point in a file; Bison itself defines a class representing a @dfn{location}, a range composed of a pair of positions (possibly spanning several files). The location class is an inner class of the parser; the name is @code{Location} by default, and may also be -renamed using @code{%define location_type "@var{class-name}"}. +renamed using @code{%define api.location.type "@var{class-name}"}. The location class treats the position as a completely opaque value. By default, the class name is @code{Position}, but this can be changed -with @code{%define position_type "@var{class-name}"}. This class must +with @code{%define api.position.type "@var{class-name}"}. This class must be supplied by the user. @@ -10161,7 +10424,7 @@ In both cases, the scanner has to implement the following methods. @deftypemethod {Lexer} {void} yyerror (Location @var{loc}, String @var{msg}) This method is defined by the user to emit an error message. The first parameter is omitted if location tracking is not active. Its type can be -changed using @code{%define location_type "@var{class-name}".} +changed using @code{%define api.location.type "@var{class-name}".} @end deftypemethod @deftypemethod {Lexer} {int} yylex () @@ -10179,7 +10442,7 @@ Return respectively the first position of the last token that @code{yylex} returned, and the first position beyond it. These methods are not needed unless location tracking is active. -The return type can be changed using @code{%define position_type +The return type can be changed using @code{%define api.position.type "@var{class-name}".} @end deftypemethod @@ -10424,10 +10687,11 @@ comma-separated list. Default is @code{java.io.IOException}. @xref{Java Scanner Interface}. @end deffn -@deffn {Directive} {%define location_type} "@var{class}" +@deffn {Directive} {%define api.location.type} "@var{class}" The name of the class used for locations (a range between two positions). This class is generated as an inner class of the parser class by @command{bison}. Default is @code{Location}. +Formerly named @code{location_type}. @xref{Java Location Values}. @end deffn @@ -10442,9 +10706,10 @@ The name of the parser class. Default is @code{YYParser} or @xref{Java Bison Interface}. @end deffn -@deffn {Directive} {%define position_type} "@var{class}" +@deffn {Directive} {%define api.position.type} "@var{class}" The name of the class used for positions. This class must be supplied by the user. Default is @code{Position}. +Formerly named @code{position_type}. @xref{Java Location Values}. @end deffn @@ -11668,8 +11933,8 @@ London, Department of Computer Science, TR-00-12 (December 2000). @uref{http://www.cs.rhul.ac.uk/research/languages/publications/tomita_style_1.ps} @end table -@node Index -@unnumbered Index +@node Index of Terms +@unnumbered Index of Terms @printindex cp @@ -11724,10 +11989,12 @@ London, Department of Computer Science, TR-00-12 (December 2000). @c LocalWords: toString deftypeivar deftypeivarx deftypeop YYParser strictfp @c LocalWords: superclasses boolean getErrorVerbose setErrorVerbose deftypecv @c LocalWords: getDebugStream setDebugStream getDebugLevel setDebugLevel url -@c LocalWords: bisonVersion deftypecvx bisonSkeleton getStartPos getEndPos +@c LocalWords: bisonVersion deftypecvx bisonSkeleton getStartPos getEndPos uint @c LocalWords: getLVal defvar deftypefn deftypefnx gotos msgfmt Corbett LALR's -@c LocalWords: subdirectory Solaris nonassociativity perror schemas Malloy -@c LocalWords: Scannerless ispell american +@c LocalWords: subdirectory Solaris nonassociativity perror schemas Malloy ints +@c LocalWords: Scannerless ispell american ChangeLog smallexample CSTYPE CLTYPE +@c LocalWords: clval CDEBUG cdebug deftypeopx yyterminate LocationType +@c LocalWords: errorVerbose @c Local Variables: @c ispell-dictionary: "american"