lex.l

一个去掉程序中#ifdef #if 等预处理条件为假的程序

%{
/*
 * scpp - selective C preprocessor
 *  Lexical scanner
 *
 * Copyright (c) 1985 by
 * Tektronix, Incorporated Beaverton, Oregon 97077
 * All rights reserved.
 *
 * Permission is hereby granted for personal, non-commercial
 * reproduction and use of this program, provided that this
 * notice and all copyright notices are included in any copy.
 */

# include <stdio.h>

# undef input
# undef unput
# define input() (*nxtin == ATTN ? nxtc() : *nxtin++)
# define YY_INPUT(buf,result,max_size) \
		{ \
                int c; \
		if (*nxtin == ATTN) { \
			c = nxtc(); \
			buf[0] = (char)c; \
			result = (c == EOF) ? 0 : 1; \
			} \
		else	{ \
			c = *nxtin++; \
			buf[0] = (char) c; \
			result = 1; \
			} \
		}
# define unput(c) unc(c)

# include "scpp.h"
# include "y.tab.h"

int lasttok = NL;	/* used to detect ^# when lex can't	*/
# define yield(t) lasttok = t; questr(yytext, yyleng); return(t)

/*
 * All input to higher levels of scpp is provided exclusively by this
 *  lexical analyzer, xxlex().
 * This routine is called xxlex() rather than yylex() because the "#if"
 *  expression parser uses a slightly different lexical analyzer (which
 *  calls xxlex()).
 */

%}
%%

"<"	{yield(LT);}
"<="	{yield(LE);}
">"	{yield(GT);}
">="	{yield(GE);}
","	{yield(CM);}
"/"	{yield(DIV);}
"%"	{yield(MOD);}
"+"	{yield(PLUS);}
"-"	{yield(MINUS);}
"<<"	{yield(LS);}
">>"	{yield(RS);}
"*"	{yield(MUL);}
"=="	{yield(EQ);}
"!="	{yield(NE);}
"&"	{yield(AND);}
"|"	{yield(OR);}
"^"	{yield(ER);}
"&&"	{yield(ANDAND);}
"||"	{yield(OROR);}
"?"	{yield(QUEST);}
":"	{yield(COLON);}
"!"	{yield(NOT);}
"~"	{yield(COMPL);}
"("	{yield(LP);}
")"	{yield(RP);}
","	{yield(CM);}
[ \t]+	{yield(WHITE);	/* whitespace */}
\\\n	{/* escaped newline */
		if (curfile->af_raw) {
			curfile->af_line++;
		}
		yield(QNL);
	}
\n	{/* unescaped newline */
		if (curfile->af_raw) {
			curfile->af_line++;
		}
		yield(NL);
	}
0x[0-9a-fA-F]+[Ll]?	{yield(INT); /* hex constant */}
[0-9]+[Ll]?		{yield(INT); /* decimal or octal constant */}
[0-9]+[Ee]([+-][0-9])?[0-9]*		|
\.[0-9]+([Ee]([+-][0-9])?[0-9]*)?	|
[0-9]+\.[0-9]*([Ee]([+-][0-9])?[0-9]*)?	{yield(FLOAT); /* floating constant */}
[a-zA-Z_][a-zA-Z0-9_]*	{yield(IDENT); /* identifier */}
\'	{yield(QUOTE);}
\"	{yield(DQUOTE);}
\\	{yield(BACKS);}
"/*"	{yield(OPENC); /* start (open) comment */}
"*/"	{yield(CLOSEC);/* finish (close) comment */}
#	{/*
	  * a control line if preceeded immediately by a newline,
	  *  even if that newline was the result of macro interpretation.
	  */
		if (lasttok == NL) {
			yield(POUNDLINE);
		}
		yield(OTHER);
	}
.	{yield(OTHER);}

%%