yacc(CP)

yacc -- yet another compiler-compiler--a parser generator

Syntax

yacc [-vdltwV -Q[y|n] ] filename

Description

The yacc command is used to generate C code that implements a parser. The program that yacc generates is based on an input file consisting of a grammar and possibly some C code fragments and internal declarations. yacc converts a context-free grammar into a set of tables for a simple automaton which executes a parsing algorithm. Code that is executed whenever a grammar production is recognized may be supplied. The grammar may be ambiguous; precedence rules are used to resolve ambiguities.

The output file containing the parser code is called y.tab.c. This program must be compiled by the C compiler; the parsing routine is called yyparse. This program must be linked with a lexical analyzer routine with the name yylex, as well as main and yyerror, an error-handling routine. lex(CP) will generate a lexical analyzer routine called yylex; if the program is linked with the yacc library, main and yyerror will be supplied.

yacc produces C code which may be compiled with C++. All functions produced and used by yacc-produced code explicitly have "C" linkage. In particular, user-supplied version of yylex() and yyerror() may be written in C++, but must have "C" linkage, and the function yyparse, must be declared extern "C" if called by C++ code.

Because file names are fixed, only one yacc process can be active in a given directory.

Options

-d: A file called y.tab.h will be generated. This file contains #define statements associating yacc-assigned token codes with the user-declared token names. This file may be included in other programs which need to access the token codes.
-l: 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.
-S: Obsolete. Silently ignored for backwards compatibility.
-t: Runtime debugging code is always generated in y.tab.c. By default, this code is not compiled. However, when yacc's -t option is used, this debugging code will be compiled. Independent of whether 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 compiled. If its value is zero, then the code will not be compiled. A program compiled without the runtime debugging code will be smaller and slightly faster.
-v: A file called y.output will be generated. This file contains a description of the parsing tables and a report on conflicts generated by ambiguities in the grammar.
-V: Print out version information on standard error.
-Q(y|n): Print out version information to output file lex.yy.c by using -Qy. The -Qn option does not print out version information and is the default.

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. If some rules are not reachable from the start symbol, this is reported.

Files

y.output
y.tab.c
y.tab.h: Defines for token names.
yacc.tmp yacc.debug yacc.acts: Temporary files.
/usr/ccs/lib/yaccpar: Parser prototype for C programs.

Standards conformance

yacc is conformant with:

X/Open Portability Guide, Issue 3, 1989