-.\" $Id: yacc.1,v 1.26 2018/06/10 00:57:07 tom Exp $
+.\" $Id: yacc.1,v 1.35 2020/09/10 19:30:12 tom Exp $
.\"
.\" .TH YACC 1 "July\ 15,\ 1990"
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+.ds N Yacc
+.ds n yacc
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+.RS +7
+.PP
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+.ft CW
..
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+.de Ee
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-.TH YACC 1 "June 9, 2018" "Berkeley Yacc" "User Commands"
+.TH YACC 1 "September 10, 2020" "Berkeley Yacc" "User Commands"
.SH NAME
-Yacc \- an LALR(1) parser generator
+\*N \- an LALR(1) parser generator
.SH SYNOPSIS
-.B yacc [ -BdgilLPrtvVy ] [ \-b
+.B \*n [ \-BdgilLPrtvVy ] [ \-b
.I file_prefix
+.B ] [ \-H
+.I defines_file
.B ] [ \-o
.I output_file
.B ] [ \-p
.B ]
.I filename
.SH DESCRIPTION
-.B Yacc
+.B \*N
reads the grammar specification in the file
.I filename
and generates an LALR(1) parser for it.
The parsers consist of a set of LALR(1) parsing tables and a driver routine
written in the C programming language.
-.B Yacc
+.B \*N
normally writes the parse tables and the driver routine to the file
-.I y.tab.c.
+.IR y.tab.c .
.PP
The following options are available:
.TP 5
create a backtracking parser (compile-time configuration for \fBbtyacc\fP).
.TP
.B \-d
-The \fB-d\fR option causes the header file
+causes the header file
.B y.tab.h
to be written.
It contains #define's for the token identifiers.
.TP
+\fB\-H \fP\fIdefines_file\fR
+causes #define's for the token identifiers
+to be written to the given \fIdefines_file\fP rather
+than the \fBy.tab.h\fP file used by the \fB\-d\fP option.
+.TP
.B \-g
The
.B \-g
option causes a graphical description of the generated LALR(1) parser to
be written to the file
.B y.dot
-in graphviz format, ready to be processed by dot(1).
+in graphviz format, ready to be processed by
+.BR dot (1).
.TP
.B \-i
-The \fB-i\fR option causes a supplementary header file
+The \fB\-i\fR option causes a supplementary header file
.B y.tab.i
to be written.
It contains extern declarations
and supplementary #define's as needed to map the conventional \fIyacc\fP
-\fByy\fP-prefixed names to whatever the \fB-p\fP option may specify.
+\fByy\fP-prefixed names to whatever the \fB\-p\fP option may specify.
The code file, e.g., \fBy.tab.c\fP is modified to #include this file
as well as the \fBy.tab.h\fP file, enforcing consistent usage of the
symbols defined in those files.
If the
.B \-l
option is not specified,
-.B yacc
+.B \*n
will insert \fI#line\fP directives in the generated code.
The \fI#line\fP directives let the C compiler relate errors in the
generated code to the user's original code.
-If the \fB-l\fR option is specified,
-.B yacc
+If the \fB\-l\fR option is specified,
+.B \*n
will not insert the \fI#line\fP directives.
\&\fI#line\fP directives specified by the user will be retained.
.TP
specify the filename for the parser file.
If this option is not given, the output filename is
the file prefix concatenated with the file suffix, e.g., \fBy.tab.c\fP.
-This overrides the \fB-b\fP option.
+This overrides the \fB\-b\fP option.
.TP
\fB\-p \fP\fIsymbol_prefix\fR
The
.B yy.
.TP
.B \-P
-create a reentrant parser, e.g., \*(``%pure-parser\*(''.
+create a reentrant parser, e.g., \*(``%pure\-parser\*(''.
.TP
.B \-r
The
.B \-r
option causes
-.B yacc
+.B \*n
to produce separate files for code and tables.
The code file is named
-.I y.code.c,
+.IR y.code.c ,
and the tables file is named
-.I y.tab.c.
+.IR y.tab.c .
The prefix \*(``\fIy.\fP\*('' can be overridden using the \fB\-b\fP option.
.TP
.B \-s
to more closely match original \fByacc\fP behavior.
.IP
Normally when \fByacc\fP sees a line such as
-.ES
+.Ex
%token OP_ADD "ADD"
-.XE
+.Ee
.IP
it notices that the quoted \*(``ADD\*('' is a valid C identifier,
and generates a #define not only for OP_ADD,
but for ADD as well,
e.g.,
-.ES
+.Ex
#define OP_ADD 257
.br
#define ADD 258
-.XE
+.Ee
.IP
The original \fByacc\fP does not generate the second \*(``\fB#define\fP\*(''.
The \fB\-s\fP option suppresses this \*(``\fB#define\fP\*(''.
The
.B \-t
option changes the preprocessor directives generated by
-.B yacc
+.B \*n
so that debugging statements will be incorporated in the compiled code.
.TP
.B \-v
.B \-y
\fByacc\fP ignores this option,
which bison supports for ostensible POSIX compatibility.
+.PP
+The \fIfilename\fP parameter is not optional.
+However, \fByacc\fP accepts a single \*(``\-\*('' to read the grammar
+from the standard input.
+A double \*(``\-\-\*('' marker denotes the end of options.
+A single \fIfilename\fP parameter is expected after a \*(``\-\-\*('' marker.
.SH EXTENSIONS
-.B yacc
+.B \*N
provides some extensions for
compatibility with bison and other implementations of yacc.
The \fB%destructor\fP and \fB%locations\fP features are available
-only if \fByacc\fP has been configured and compiled to support the
+only if \fB\*n\fP has been configured and compiled to support the
back-tracking (\fBbtyacc\fP) functionality.
The remaining features are always available:
.TP
+\fB %code\fP \fIkeyword\fP { \fIcode\fP }
+Adds the indicated source \fIcode\fP at a given point in the output file.
+The optional \fIkeyword\fP tells \fB\*n\fP where to insert the \fIcode\fP:
+.RS 7
+.TP 5
+\fBtop\fP
+just after the version-definition in the generated code-file.
+.TP 5
+\fBrequires\fP
+just after the declaration of public parser variables.
+If the \fB\-d\fP option is given, the code is inserted at the
+beginning of the defines-file.
+.TP 5
+\fBprovides\fP
+just after the declaration of private parser variables.
+If the \fB\-d\fP option is given, the code is inserted at the
+end of the defines-file.
+.RE
+.IP
+If no \fIkeyword\fP is given, the code is inserted at the
+beginning of the section of code copied verbatim from the source file.
+Multiple \fB%code\fP directives may be given;
+\fB\*n\fP inserts those into the corresponding code- or defines-file
+in the order that they appear in the source file.
+.TP
\fB %destructor\fP { \fIcode\fP } \fIsymbol+\fP
defines code that is invoked when a symbol is automatically
discarded during error recovery.
pointers to dynamically allocated memory.
.IP
The bracketed \fIcode\fP is invoked whenever the parser discards one of
-the symbols. Within \fIcode\fP, \*(``\fB$$\fP\*('' or
+the symbols.
+Within \fIcode\fP, \*(``\fB$$\fP\*('' or
\*(``\fB$<tag>$\fP\*('' designates the semantic value associated with the
-discarded symbol, and \*(``\fB@$\fP\*('' designates its location (see
+discarded symbol, and \*(``\fB@$\fP\*('' designates its location (see
\fB%locations\fP directive).
.IP
A per-symbol destructor is defined by listing a grammar symbol
-in \fIsymbol+\fP. A per-type destructor is defined by listing
+in \fIsymbol+\fP. A per-type destructor is defined by listing
a semantic type tag (e.g., \*(``<some_tag>\*('') in \fIsymbol+\fP; in this
case, the parser will invoke \fIcode\fP whenever it discards any grammar
symbol that has that semantic type tag, unless that symbol has its own
tells \fByacc\fP the expected number of shift/reduce conflicts.
That makes it only report the number if it differs.
.TP
-\fB %expect-rr\fP \fInumber\fP
+\fB %expect\-rr\fP \fInumber\fP
tell \fByacc\fP the expected number of reduce/reduce conflicts.
That makes it only report the number if it differs.
This is (unlike bison) allowable in LALR parsers.
.TP
\fB %locations\fP
-tells \fByacc\fP to enable management of position information associated
+tells \fByacc\fP to enable management of position information associated
with each token, provided by the lexer in the global variable \fByylloc\fP,
similar to management of semantic value information provided in \fByylval\fP.
.IP
As for semantic values, locations can be referenced within actions using
\fB@$\fP to refer to the location of the left hand side symbol, and \fB@N\fP
(\fBN\fP an integer) to refer to the location of one of the right hand side
-symbols. Also as for semantic values, when a rule is matched, a default
+symbols.
+Also as for semantic values, when a rule is matched, a default
action is used the compute the location represented by \fB@$\fP as the
beginning of the first symbol and the end of the last symbol in the right
-hand side of the rule. This default computation can be overridden by
+hand side of the rule.
+This default computation can be overridden by
explicit assignment to \fB@$\fP in a rule action.
.IP
The type of \fByylloc\fP is \fBYYLTYPE\fP, which is defined by default as:
-.ES
+.Ex
typedef struct YYLTYPE {
int first_line;
int first_column;
int last_line;
int last_column;
} YYLTYPE;
-.XE
+.Ee
.IP
\fBYYLTYPE\fP can be redefined by the user
(\fBYYLTYPE_IS_DEFINED\fP must be defined, to inhibit the default)
redefined by the user.
.IP
This directive adds a \fBYYLTYPE\fP parameter to \fByyerror()\fP.
-If the \fB%pure-parser\fP directive is present,
+If the \fB%pure\-parser\fP directive is present,
a \fBYYLTYPE\fP parameter is added to \fByylex()\fP calls.
.TP
-\fB %lex-param\fP { \fIargument-declaration\fP }
+\fB %lex\-param\fP { \fIargument-declaration\fP }
By default, the lexer accepts no parameters, e.g., \fByylex()\fP.
Use this directive to add parameter declarations for your customized lexer.
.TP
-\fB %parse-param\fP { \fIargument-declaration\fP }
+\fB %parse\-param\fP { \fIargument-declaration\fP }
By default, the parser accepts no parameters, e.g., \fByyparse()\fP.
Use this directive to add parameter declarations for your customized parser.
.TP
-\fB %pure-parser\fP
+\fB %pure\-parser\fP
Most variables (other than \fByydebug\fP and \fByynerrs\fP) are
allocated on the stack within \fByyparse\fP, making the parser reasonably
reentrant.
.TP
-\fB %token-table\fP
+\fB %token\-table\fP
Make the parser's names for tokens available in the \fByytname\fP array.
However,
-.B yacc
+.B \*n
does not predefine \*(``$end\*('', \*(``$error\*(''
or \*(``$undefined\*('' in this array.
.SH PORTABILITY
According to Robert Corbett,
-.ES
- Berkeley Yacc is an LALR(1) parser generator. Berkeley Yacc has been made
-as compatible as possible with AT&T Yacc. Berkeley Yacc can accept any input
-specification that conforms to the AT&T Yacc documentation. Specifications
-that take advantage of undocumented features of AT&T Yacc will probably be
-rejected.
-.XE
+.Ex
+Berkeley Yacc is an LALR(1) parser generator. Berkeley Yacc
+has been made as compatible as possible with AT&T Yacc.
+Berkeley Yacc can accept any input specification that
+conforms to the AT&T Yacc documentation. Specifications
+that take advantage of undocumented features of AT&T Yacc
+will probably be rejected.
+.Ee
.PP
The rationale in
-.ES
+.Ex
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/yacc.html
-.XE
+.Ee
.PP
documents some features of AT&T yacc which are no longer required for POSIX
compliance.
.bP
\fBYacc\fP accepts an equals mark preceding the left curly brace
of an action (as in the original grammar file \fBftp.y\fP):
-.ES
- | STAT CRLF
- = {
- statcmd();
- }
-.XE
+.Ex
+ | STAT CRLF
+ = {
+ statcmd();
+ }
+.Ee
.bP
\fBYacc\fP and bison emit code in different order, and in particular bison
makes forward reference to common functions such as yylex, yyparse and
Bison's support for \*(``%expect\*('' is broken in more than one release.
For best results using bison, delete that directive.
.bP
-Bison has no equivalent for some of \fByacc\fP's commmand-line options,
+Bison has no equivalent for some of \fByacc\fP's command-line options,
relying on directives embedded in the grammar file.
.bP
Bison's \*(``\fB\-y\fP\*('' option does not affect bison's lack of support for
features of AT&T yacc which were deemed obsolescent.
.bP
\fBYacc\fP accepts multiple parameters
-with \fB%lex-param\fP and \fB%parse-param\fP in two forms
-.ES
+with \fB%lex\-param\fP and \fB%parse\-param\fP in two forms
+.Ex
{type1 name1} {type2 name2} ...
{type1 name1, type2 name2 ...}
-.XE
+.Ee
.IP
Bison accepts the latter (though undocumented), but depending on the
release may generate bad code.
.bP
-Like bison, \fByacc\fP will add parameters specified via \fB%parse-param\fP
+Like bison, \fByacc\fP will add parameters specified via \fB%parse\-param\fP
to \fByyparse\fP, \fByyerror\fP and (if configured for back-tracking)
to the destructor declared using \fB%destructor\fP.
Bison puts the additional parameters \fIfirst\fP for
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