C/C++ Interactive Guide/c-cplusplus-interactive-guide.iso/c_ref/csource2/sclib_2/2_5/v6n5018a.txt

Text File | 1995-11-01 | 9.2 KB | 304 lines

/***************************  yref2.y  ****************************/
/*  This version expands the grammar rules so that a more involved
    C source file can be successfully parsed to find identifiers,
    their line number locations, and where they are declared. Use
    "yylex.c" as a test input file, then experiment by making changes
    in both the input file and the grammar rules. */

      /* Beginning of declarations section */
%{
         int line_num = 1;
         char identifier[32];
%}

      /* Union defined for sending multiple data types from
         yylex() to yyparse() via the reserved internal yacc
         variable yylval. */
%union
    {
    int  char_value;       /* value of single characters */
    char *str_value;       /* value of strings */
    };

%token   <str_value> SC_SPEC, TYPE_SPEC, QUAL_SPEC, STRUCT_UNION
%token   <str_value> KEYWORD, IDENTIFIER, ENUM

%token   <char_value> STRING CHAR_CONST PRE_PROC OPERATOR NUM_CONST

%left ','
%right '='
%left  OPERATOR
%left '*'
%left '(' ')' '[' ']' '.'
%start   source_file

%%    /* End of declarations, beginning of grammar rules section. */


/*  User-defined grammar rules and associated actions go here.
    The actual rules presented here are a partial specification
    of the C language grammar, based on the ANSI X3J11 draft
    (November 9, 1987, Appendix A) for the "external definitions"
    and "declarations" rules, and on K&R (1978, pages 214 to 219)
    for the "statements" and "expressions" rules. Note that the
    rules presented here have been freely adapted, and often differ
    substantially from the original sources cited.  */

/* external definitions */
source_file: /* nothing */
         | external_declaration
                { printf("\n\t\t\t*** Back to top level ***\n"); }
         | source_file external_declaration
                { printf("\n\t\t\t*** Back to top level ***\n"); }
         ;

external_declaration:
           function_definition
         | declaration
         ;

function_definition:
           declarator compound_statement
                { printf("\n\t*** End of function definition -- Type 1 ***"); }
         | declarator declaration_list compound_statement
                { printf("\n\t*** End of function definition -- Type 2 ***"); }
         | declaration_specifiers declarator compound_statement
                { printf("\n\t*** End of function definition -- Type 3 ***"); }
         | declaration_specifiers declarator declaration_list compound_statement
                { printf("\n\t*** End of function definition -- Type 4 ***"); }
         ;

/* Declarations */
declaration:
           declaration_specifiers ';'
         | declaration_specifiers init_declarator_list ';'
         ;

declaration_specifiers:
           storage_class_specifier
         | storage_class_specifier declaration_specifiers
         | type_specifier
         | type_specifier declaration_specifiers
         | type_qualifier
         | type_qualifier declaration_specifiers
         ;

init_declarator_list:
           init_declarator
         | init_declarator_list ',' init_declarator
         ;

init_declarator:
           declarator
         | declarator '=' initializer
         ;

initializer:
           expression
         | '{' initializer_list '}'
         | '{' initializer_list ',' '}'
         ;

initializer_list:
           initializer
         | initializer_list ',' initializer
         ;

storage_class_specifier:
           SC_SPEC
         ;

type_specifier:
           TYPE_SPEC
         ;

type_qualifier:
           QUAL_SPEC
         ;

declarator:
           direct_declarator
         | pointer  direct_declarator
                { printf(" (Pointer)"); }
         ;

direct_declarator:
           IDENTIFIER
                { printf("\n\tLine %3d: %s  Basic declarator", line_num, $1); }
         | '(' declarator ')'
                { printf(" -- Parenthesized declarator"); }
         | direct_declarator '[' ']'  %prec '*'
                { printf(" --  Array declarator 1"); }
         | direct_declarator '[' constant ']' %prec '*' /* Variant */
                { printf(" --  Array declarator 2"); }
         | direct_declarator '(' parameter_type_list ')' %prec '*'
                { printf(" --  Function declarator 1"); }
         | direct_declarator '(' ')' %prec '*'
                { printf(" --  Function declarator 2"); }
         | direct_declarator '(' identifier_list ')' %prec '*'
                { printf(" --  Function declarator 3"); }
         ;

pointer:
           '*'
         | '*' type_specifier_list
         | '*' pointer
         | '*' type_specifier_list pointer
         ;

type_specifier_list:
           type_specifier
         | type_specifier_list type_specifier
         ;

parameter_type_list:
           parameter_list
                { printf("\n\tLine %3d: ANSI Function Prototype", line_num); }
         ;

parameter_list:
           parameter_declaration
         | parameter_list ',' parameter_declaration
         ;

parameter_declaration:
           declaration_specifiers declarator
         | declaration_specifiers
         | declaration_specifiers abstract_declarator
         ;

abstract_declarator:
           pointer
         | direct_abstract_declarator
         | pointer direct_abstract_declarator
         ;

direct_abstract_declarator:
           '(' abstract_declarator ')'
         | '[' ']'
         | '[' constant ']'
         | direct_abstract_declarator '[' ']'
         | direct_abstract_declarator '[' constant ']'
         | '(' ')'
         | '(' parameter_type_list ')'
         | direct_abstract_declarator '(' ')'
         | direct_abstract_declarator '(' parameter_type_list ')'
         ;

identifier_list:
           IDENTIFIER
                { printf("\n\tLine %3d: Identifier: %14s", line_num, $1); }
         | identifier_list ',' IDENTIFIER
                { printf("\n\tLine %3d: Identifier: %14s", line_num, $3); }
         ;

/* Statements */
statement:
           compound_statement
         | expression ';'
         | KEYWORD '(' expression ')' statement
         | KEYWORD for_construct statement
         | KEYWORD statement
         | KEYWORD constant ':' statement
         | KEYWORD ':' statement
         | KEYWORD IDENTIFIER ';'
                { printf("\n\tLine %3d: Identifier: %14s", line_num, $2); }
         | IDENTIFIER ':' statement
                { printf("\n\tLine %3d: Identifier: %14s", line_num, $1); }
         | ';'
         ;

compound_statement:
           '{' '}'
         | '{' declaration_list '}'
         | '{' statement_list '}'
         | '{' declaration_list statement_list '}'
         ;

declaration_list:
           declaration
         | declaration_list declaration
         ;

statement_list:
           statement
         | statement_list statement
         ;

for_construct:
           '(' ';' ';' ')'
         | '(' expression ';' ';' ')'
         | '(' ';' expression ';' ')'
         | '(' ';' ';' expression ')'
         | '(' expression ';' expression ';' ')'
         | '(' ';' expression ';' expression ')'
         | '(' expression ';' expression ';' expression ')'
         ;

/* Expressions */
expression:
           primary_expression
         | '*' expression   %prec '*'
         | OPERATOR expression
         | expression OPERATOR
         | expression OPERATOR expression
         | expression '=' expression
         | expression '=' '=' expression  %prec '*'
         | expression '*' expression  %prec OPERATOR
         | expression ',' expression
         ;

primary_expression:
           IDENTIFIER
                { printf("\n\tLine %3d: Identifier: %14s", line_num, $1); }
         | constant
         | STRING
         | '(' expression ')'
         | primary_expression '(' ')'
                { printf("\n\t\t\t ** End of function call **"); }
         | primary_expression '(' expression ')'
                { printf("\n\t\t\t ** End of function call **"); }
         | primary_expression '[' expression ']'
                { printf("\n\t\t\t ** End of array reference **"); }
         | primary_expression '.' IDENTIFIER
                { printf("\n\tLine %3d: Identifier: %14s", line_num, $3);
                  printf("\n\t\t\t ** End of structure reference **"); }
         ;

constant:
           CHAR_CONST
         | NUM_CONST
         ;


%%    /* End of grammar rules section, beginning of program section. */

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>

#include "yylex.c"

/* Required by yacc */
int yyerror( message)

         char *message;
{
         printf("\n\tLine %d, %s", line_num, message);
}

/* Simplest version of main() -- yyparse continuously calls yylex to
   read input until yylex returns zero at end of file.  Main() will
   usually perform additional tasks, such as handling command line
   arguments, opening input streams, error handling, etc. */

main()
{
      /* yyparse is a finite state machine generated by yacc
         based on the user's grammar rule and action sequences. */

         yyparse();
}