X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/0f39aab92ab23bc067a3aa102bb56a600c045775..6b0d38ab2c1839b38dc6a994223a432f07c3cff9:/doc/bison.texinfo diff --git a/doc/bison.texinfo b/doc/bison.texinfo index 6cef9b5e..ef803899 100644 --- a/doc/bison.texinfo +++ b/doc/bison.texinfo @@ -1373,7 +1373,7 @@ main (void) When @code{yyparse} detects a syntax error, it calls the error reporting function @code{yyerror} to print an error message (usually but not -always @code{"parse error"}). It is up to the programmer to supply +always @code{"syntax error"}). It is up to the programmer to supply @code{yyerror} (@pxref{Interface, ,Parser C-Language Interface}), so here is the definition we will use: @@ -1583,7 +1583,7 @@ line: '\n' @end example This addition to the grammar allows for simple error recovery in the -event of a parse error. If an expression that cannot be evaluated is +event of a syntax error. If an expression that cannot be evaluated is read, the error will be recognized by the third rule for @code{line}, and parsing will continue. (The @code{yyerror} function is still called upon to print its message as well.) The action executes the statement @@ -2302,8 +2302,8 @@ can be done with two @var{Prologue} blocks, one before and one after the @} %@{ -static void yyprint(FILE *, int, YYSTYPE); -#define YYPRINT(F, N, L) yyprint(F, N, L) +static void print_token_value (FILE *, int, YYSTYPE); +#define YYPRINT(F, N, L) print_token_value (F, N, L) %@} @dots{} @@ -3671,7 +3671,7 @@ Generate the code processing the locations (@pxref{Action Features, ,Special Features for Use in Actions}). This mode is enabled as soon as the grammar uses the special @samp{@@@var{n}} tokens, but if your grammar does not use it, using @samp{%locations} allows for more -accurate parse error messages. +accurate syntax error messages. @end deffn @deffn {Directive} %name-prefix="@var{prefix}" @@ -3847,19 +3847,20 @@ If you use a reentrant parser, you can optionally pass additional parameter information to it in a reentrant way. To do so, use the declaration @code{%parse-param}: -@deffn {Directive} %parse-param @{@var{argument-declaration}@}, @{@var{argument-name}@} +@deffn {Directive} %parse-param @{@var{argument-declaration}@} @findex %parse-param -Declare that @code{argument-name} is an additional @code{yyparse} -argument. This argument is also passed to @code{yyerror}. The -@var{argument-declaration} is used when declaring functions or -prototypes. +Declare that an argument declared by @code{argument-declaration} is an +additional @code{yyparse} argument. This argument is also passed to +@code{yyerror}. The @var{argument-declaration} is used when declaring +functions or prototypes. The last identifier in +@var{argument-declaration} must be the argument name. @end deffn Here's an example. Write this in the parser: @example -%parse-param @{int *nastiness@}, @{nastiness@} -%parse-param @{int *randomness@}, @{randomness@} +%parse-param @{int *nastiness@} +%parse-param @{int *randomness@} @end example @noindent @@ -4090,18 +4091,18 @@ If you wish to pass the additional parameter data to @code{yylex}, use @code{%lex-param} just like @code{%parse-param} (@pxref{Parser Function}). -@deffn {Directive} lex-param @{@var{argument-declaration}@}, @{@var{argument-name}@} +@deffn {Directive} lex-param @{@var{argument-declaration}@} @findex %lex-param -Declare that @code{argument-name} is an additional @code{yylex} -argument. +Declare that @code{argument-declaration} is an additional @code{yylex} +argument declaration. @end deffn For instance: @example -%parse-param @{int *nastiness@}, @{nastiness@} -%lex-param @{int *nastiness@}, @{nastiness@} -%parse-param @{int *randomness@}, @{randomness@} +%parse-param @{int *nastiness@} +%lex-param @{int *nastiness@} +%parse-param @{int *randomness@} @end example @noindent @@ -4134,7 +4135,7 @@ int yyparse (int *nastiness, int *randomness); @cindex parse error @cindex syntax error -The Bison parser detects a @dfn{parse error} or @dfn{syntax error} +The Bison parser detects a @dfn{syntax error} or @dfn{parse error} whenever it reads a token which cannot satisfy any syntax rule. An action in the grammar can also explicitly proclaim an error, using the macro @code{YYERROR} (@pxref{Action Features, ,Special Features for Use @@ -4143,14 +4144,14 @@ in Actions}). The Bison parser expects to report the error by calling an error reporting function named @code{yyerror}, which you must supply. It is called by @code{yyparse} whenever a syntax error is found, and it -receives one argument. For a parse error, the string is normally -@w{@code{"parse error"}}. +receives one argument. For a syntax error, the string is normally +@w{@code{"syntax error"}}. @findex %error-verbose If you invoke the directive @code{%error-verbose} in the Bison declarations section (@pxref{Bison Declarations, ,The Bison Declarations Section}), then Bison provides a more verbose and specific error message -string instead of just plain @w{@code{"parse error"}}. +string instead of just plain @w{@code{"syntax error"}}. The parser can detect one other kind of error: stack overflow. This happens when the input contains constructions that are very deeply @@ -4190,7 +4191,7 @@ void yyerror (const char *msg); /* Yacc parsers. */ void yyerror (YYLTYPE *locp, const char *msg); /* GLR parsers. */ @end example -If @samp{%parse-param @{int *nastiness@}, @{nastiness@}} is used, then: +If @samp{%parse-param @{int *nastiness@}} is used, then: @example void yyerror (int *randomness, const char *msg); /* Yacc parsers. */ @@ -4207,10 +4208,10 @@ convention of @code{yylex} @emph{and} the calling convention of %locations /* Pure yylex. */ %pure-parser -%lex-param @{int *nastiness@}, @{nastiness@} +%lex-param @{int *nastiness@} /* Pure yyparse. */ -%parse-param @{int *nastiness@}, @{nastiness@} -%parse-param @{int *randomness@}, @{randomness@} +%parse-param @{int *nastiness@} +%parse-param @{int *randomness@} @end example @noindent @@ -5156,7 +5157,7 @@ provided which addresses this issue. @cindex error recovery @cindex recovery from errors -It is not usually acceptable to have a program terminate on a parse +It is not usually acceptable to have a program terminate on a syntax error. For example, a compiler should recover sufficiently to parse the rest of the input file and check it for errors; a calculator should accept another expression. @@ -5259,7 +5260,7 @@ 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. -For example, suppose that on a parse error, an error handling routine is +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 once again commence. The next symbol returned by the lexical scanner is probably correct. The previous look-ahead token ought to be discarded @@ -5646,7 +5647,7 @@ after having reduced a rule that produced an @code{exp}, the control flow jumps to state 2. If there is no such transition on a nonterminal symbol, and the lookahead is a @code{NUM}, then this token is shifted on the parse stack, and the control flow jumps to state 1. Any other -lookahead triggers a parse error.'' +lookahead triggers a syntax error.'' @cindex core, item set @cindex item set core @@ -5714,7 +5715,7 @@ because of the item @samp{exp -> exp . '+' exp}, if the lookahead if @samp{+}, it will be shifted on the parse stack, and the automaton control will jump to state 4, corresponding to the item @samp{exp -> exp '+' . exp}. Since there is no default action, any other token than -those listed above will trigger a parse error. +those listed above will trigger a syntax error. The state 3 is named the @dfn{final state}, or the @dfn{accepting state}: @@ -5980,15 +5981,15 @@ Here is an example of @code{YYPRINT} suitable for the multi-function calculator (@pxref{Mfcalc Decl, ,Declarations for @code{mfcalc}}): @smallexample -#define YYPRINT(file, type, value) yyprint (file, type, value) +#define YYPRINT(file, type, value) print_token_value (file, type, value) static void -yyprint (FILE *file, int type, YYSTYPE value) +print_token_value (FILE *file, int type, YYSTYPE value) @{ if (type == VAR) - fprintf (file, " %s", value.tptr->name); + fprintf (file, "%s", value.tptr->name); else if (type == NUM) - fprintf (file, " %d", value.val); + fprintf (file, "%d", value.val); @} @end smallexample @@ -6300,7 +6301,7 @@ The predefined token onto which all undefined values returned by 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 parse error, the +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. @@ -6415,7 +6416,7 @@ symbols and parser action. @xref{Tracing, ,Tracing Your Parser}. @deffn {Macro} yyerrok Macro to cause parser to recover immediately to its normal mode -after a parse error. @xref{Error Recovery}. +after a syntax error. @xref{Error Recovery}. @end deffn @deffn {Function} yyerror @@ -6448,7 +6449,7 @@ variable within @code{yyparse}, and its address is passed to @end deffn @deffn {Variable} yynerrs -Global variable which Bison increments each time there is a parse error. +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 @@ -6498,7 +6499,7 @@ Bison declaration to assign left associativity to token(s). @xref{Precedence Decl, ,Operator Precedence}. @end deffn -@deffn {Directive} %lex-param @{@var{argument-declaration}@}. @{@var{argument-name}"@} +@deffn {Directive} %lex-param @{@var{argument-declaration}@} Bison declaration to specifying an additional parameter that @code{yylex} should accept. @xref{Pure Calling,, Calling Conventions for Pure Parsers}. @@ -6530,7 +6531,7 @@ Bison declaration to set the name of the parser file. @xref{Decl Summary}. @end deffn -@deffn {Directive} %parse-param @{@var{argument-declaration}@}, @{@var{argument-name}@} +@deffn {Directive} %parse-param @{@var{argument-declaration}@} Bison declaration to specifying an additional parameter that @code{yyparse} should accept. @xref{Parser Function,, The Parser Function @code{yyparse}}. @@ -6715,10 +6716,6 @@ A grammar symbol standing for a grammatical construct that can be expressed through rules in terms of smaller constructs; in other words, a construct that is not a token. @xref{Symbols}. -@item Parse error -An error encountered during parsing of an input stream due to invalid -syntax. @xref{Error Recovery}. - @item Parser A function that recognizes valid sentences of a language by analyzing the syntax structure of a set of tokens passed to it from a lexical @@ -6771,6 +6768,10 @@ A data structure where symbol names and associated data are stored during parsing to allow for recognition and use of existing information in repeated uses of a symbol. @xref{Multi-function Calc}. +@item Syntax error +An error encountered during parsing of an input stream due to invalid +syntax. @xref{Error Recovery}. + @item Token A basic, grammatically indivisible unit of a language. The symbol that describes a token in the grammar is a terminal symbol.