Writing re-entrant lexer with Flex
- by Viet
I'm newbie to flex. I'm trying to write a simple re-entrant lexer/scanner with flex. The lexer definition goes below. I get stuck with compilation errors as shown below (yyg issue):
reentrant.l:
/* Definitions */
digit [0-9]
letter [a-zA-Z]
alphanum [a-zA-Z0-9]
identifier [a-zA-Z_][a-zA-Z0-9_]+
integer [0-9]+
natural [0-9]*[1-9][0-9]*
decimal ([0-9]+\.|\.[0-9]+|[0-9]+\.[0-9]+)
%{
#include <stdio.h>
#define ECHO fwrite(yytext, yyleng, 1, yyout)
int totalNums = 0;
%}
%option reentrant
%option prefix="simpleit_"
%%
^(.*)\r?\n printf("%d\t%s", yylineno++, yytext);
%%
/* Routines */
int yywrap(yyscan_t yyscanner)
{
return 1;
}
int main(int argc, char* argv[])
{
yyscan_t yyscanner;
if(argc < 2) {
printf("Usage: %s fileName\n", argv[0]);
return -1;
}
yyin = fopen(argv[1], "rb");
yylex(yyscanner);
return 0;
}
Compilation errors:
vietlq@mylappie:~/Desktop/parsers/reentrant$ gcc lex.simpleit_.c
reentrant.l: In function ‘main’:
reentrant.l:44: error: ‘yyg’ undeclared (first use in this function)
reentrant.l:44: error: (Each undeclared identifier is reported only once
reentrant.l:44: error: for each function it appears in.)
