Extracted CMake lexer

cmake.l

%{
#include <stdio.h>
#include <errno.h>
int file_num;
int file_num_max;
char **files;
extern int errno;
%}

%pointer
%x STRING

MAKEVAR \$\([A-Za-z0-9_]*\)

%%

\n {
  fprintf(stderr, "newline\n");
  return 1;
}

#.* {
  fprintf(stderr, "comment: '%s'\n", yytext);
}

\( {
  fprintf(stderr, "lparen\n");
  return 1;
}

\) {
  fprintf(stderr, "rparen\n");
  return 1;
}

[A-Za-z_][A-Za-z0-9_]+ {
  fprintf(stderr, "identifier: '%s'\n", yytext);
  return 1;
}

({MAKEVAR}|[^ \t\r\n\(\)#\\\"]|\\.)({MAKEVAR}|[^ \t\r\n\(\)#\\\"]|\\.|\"({MAKEVAR}|[^\r\n\(\)#\\\"]|\\.)*\")* {
  fprintf(stderr, "unquoted-argument: '%s'\n", yytext);
  return 1;
}

\" {
  fprintf(stderr, "quoted: '%s'\n", yytext);
  BEGIN(STRING);
}

<STRING>([^\\\n\"]|\\(.|\n))+ {
  fprintf(stderr, "string1: '%s'\n", yytext);
}

<STRING>\n {
  fprintf(stderr, "string2: '%s'\n", yytext);
}

<STRING>\" {
  fprintf(stderr, "string3: '%s'\n", yytext);
  BEGIN(INITIAL);
  return 1;
}

<STRING>. {
  fprintf(stderr, "string4: '%s'\n", yytext);
}

<STRING><<EOF>> {
  fprintf(stderr, "string5: '%s'\n", yytext);
  BEGIN(INITIAL);
  return 1;
}

[ \t\r] {
  fprintf(stderr, "ws: '%s'\n", yytext);
}

. {
  fprintf(stderr, "badchar: '%s'\n", yytext);
  return 1;
}

<<EOF>> {
  fprintf(stderr, "eof\n");
  return 0;
}

%%

int main(int argc, char *argv[]) {
	file_num=1;
	file_num_max = argc;
	files = argv;
	if ( argc > 1 ) {
		if ( (yyin = fopen(argv[file_num],"r")) == 0 ) {
			perror(argv[file_num]);
			exit(1);
		}
	}
	while( yylex() )
		;
	return 0;
}

int yywrap() {
	fclose(yyin);
	if ( ++file_num < file_num_max ) {
		if ( (yyin = fopen(files[file_num],"r")) == 0 ) {
			perror(files[file_num]);
			exit(1);
		}
		return 0;
	} else {
		return 1;
	}
}