plan9-yacc(1) [debian man page]
YACC(1) General Commands Manual YACC(1) NAME
yacc - yet another compiler-compiler SYNOPSIS
yacc [ option ... ] grammar DESCRIPTION
Yacc converts a context-free grammar and translation code into a set of tables for an LR(1) parser and translator. The grammar may be ambiguous; specified precedence rules are used to break ambiguities. The output file, y.tab.c, must be compiled by the C compiler to produce a program This program must be loaded with a lexical analyzer func- tion, yylex(void) (often generated by lex(1)), with a main(int argc, char *argv[]) program, and with an error handling routine, yyer- ror(char*). The options are -o output Direct output to the specified file instead of y.tab.c. -Dn Create file y.debug, containing diagnostic messages. To incorporate them in the parser, compile it with preprocessor symbol yydebug defined. The amount of diagnostic output from the parser is regulated by value n. The value 0 reports errors; 1 reports reductions; higher values (up to 4) include more information about state transitions. -v Create file y.output, containing a description of the parsing tables and of conflicts arising from ambiguities in the grammar. -d Create file y.tab.h, containing #define statements that associate yacc-assigned `token codes' with user-declared `token names'. Include it in source files other than y.tab.c to give access to the token codes. -s stem Change the prefix of the file names y.tab.c, y.tab.h, y.debug, and y.output to stem. -S Write a parser that uses Stdio instead of the print routines in libc. -l Disable #line directives in the generated parser. -a Generate a parser that takes an argument of type Yyarg and passes this argument to each invocation of the lexer function, yylex. Yyarg contains per-instance state and a single user-visible member, arg, of type void*. The specification of yacc itself is essentially the same as the UNIX version described in the references mentioned below. Besides the -D option, the main relevant differences are: The interface to the C environment is by default through <libc.h> rather than <stdio.h>; the -S option reverses this. The parser accepts UTF input text (see utf(7)), which has a couple of effects. First, the return value of yylex() no longer fits in a short; second, the starting value for non-terminals is now 0xE000 rather than 257. The generated parser can be recursive: actions can call yyparse, for example to implement a sort of #include statement in an inter- preter. Finally, some undocumented inner workings of the parser have been changed, which may affect programs that know too much about its structure. FILES
y.output y.tab.c y.tab.h y.debug y.tmp.* temporary file y.acts.* temporary file /lib/yaccpar parser prototype /lib/yaccpars parser prototype using stdio SOURCE
/src/cmd/yacc.c SEE ALSO
lex(1) S. C. Johnson and R. Sethi, ``Yacc: A parser generator'', Unix Research System Programmer's Manual, Tenth Edition, Volume 2 B. W. Kernighan and Rob Pike, The UNIX Programming Environment, Prentice Hall, 1984 BUGS
The parser may not have full information when it writes to y.debug so that the names of the tokens returned by may be missing. YACC(1)
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yacc(1) User Commands yacc(1) NAME
yacc - yet another compiler-compiler SYNOPSIS
/usr/ccs/bin/yacc [-dltVv] [-b file_prefix] [ -Q [y | n] ] [-P parser] [-p sym_prefix] file DESCRIPTION
The yacc command converts a context-free grammar into a set of tables for a simple automaton that executes an LALR(1) parsing algorithm. The grammar may be ambiguous. Specified precedence rules are used to break ambiguities. The output file, y.tab.c, must be compiled by the C compiler to produce a function yyparse(). This program must be loaded with the lexical analyzer program, yylex(), as well as main() and yyerror(), an error handling routine. These routines must be supplied by the user. The lex(1) command is useful for creating lexical analyzers usable by yacc. OPTIONS
The following options are supported: -b file_prefix Uses file_prefix instead of y as the prefix for all output files. The code file y.tab.c, the header file y.tab.h (created when -d is specified), and the description file y.output (created when -v is specified), will be changed to file_pre- fix.tab.c, file_prefix.tab.h, and file_prefix.output, respectively. -d Generates the file y.tab.h with the #define statements that associate the yacc user-assigned "token codes" with the user- declared "token names". This association allows source files other than y.tab.c to access the token codes. -l Specifies that the code produced in y.tab.c will not contain any #line constructs. This option should only be used after the grammar and the associated actions are fully debugged. -p sym_prefix Uses sym_prefix instead of yy as the prefix for all external names produced by yacc. The names affected include the func- tions yyparse(), yylex() and yyerror(), and the variables yylval, yychar and yydebug. (In the remainder of this section, the six symbols cited are referenced using their default names only as a notational convenience.) Local names may also be affected by the -p option. However, the -p option does not affect #define symbols generated by yacc. -P parser Allows you to specify the parser of your choice instead of /usr/ccs/bin/yaccpar. For example, you can specify: example% yacc -P ~/myparser parser.y -Q[y|n] The -Qy option puts the version stamping information in y.tab.c. This allows you to know what version of yacc built the file. The -Qn option (the default) writes no version information. -t Compiles runtime debugging code by default. Runtime debugging code is always generated in y.tab.c under conditional compi- lation control. By default, this code is not included when y.tab.c is compiled. Whether or not the -t option is used, the runtime debugging code is under the control of YYDEBUG , a preprocessor symbol. If YYDEBUG has a non-zero value, then the debugging code is included. If its value is 0, then the code will not be included. The size and execution time of a program produced without the runtime debugging code will be smaller and slightly faster. -v Prepares the file y.output, which contains a description of the parsing tables and a report on conflicts generated by ambi- guities in the grammar. -V Prints on the standard error output the version information for yacc. OPERANDS
The following operand is required: file A path name of a file containing instructions for which a parser is to be created. EXAMPLES
Example 1: Accessing the yacc library Access to the yacc library is obtained with library search operands to cc. To use the yacc library main: example% cc y.tab.c -ly Both the lex library and the yacc library contain main. To access the yacc main: example% cc y.tab.c lex.yy.c -ly -ll This ensures that the yacc library is searched first, so that its main is used. The historical yacc libraries have contained two simple functions that are normally coded by the application programmer. These library functions are similar to the following code: #include <locale.h> int main(void) { extern int yyparse(); setlocale(LC_ALL, ""); /* If the following parser is one created by lex, the application must be careful to ensure that LC_CTYPE and LC_COLLATE are set to the POSIX locale. */ (void) yyparse(); return(0); } #include <stdio.h> int yyerror(const char *msg) { (void) fprintf(stderr, "%s ", msg); return(0); } ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of yacc: LANG, LC_ALL, LC_CTYPE, LC_MES- SAGES, and NLSPATH. yacc can handle characters from EUC primary and supplementary codesets as one-token symbols. EUC codes may only be single character quoted terminal symbols. yacc expects yylex() to return a wide character (wchar_t) value for these one-token symbols. EXIT STATUS
The following exit values are returned: 0 Successful completion. >0 An error occurred. FILES
y.output state transitions of the generated parser y.tab.c source code of the generated parser y.tab.h header file for the generated parser yacc.acts temporary file yacc.debug temporary file yacc.tmp temporary file yaccpar parser prototype for C programs ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWbtool | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
cc(1B), lex(1), attributes(5), environ(5), standards(5) DIAGNOSTICS
The number of reduce-reduce and shift-reduce conflicts is reported on the standard error output. A more detailed report is found in the y.output file. Similarly, if some rules are not reachable from the start symbol, this instance is also reported. NOTES
Because file names are fixed, at most one yacc process can be active in a given directory at a given time. Users are encouraged to avoid using '$' as part of any identifier name. SunOS 5.10 20 Dec 1996 yacc(1)