scc

cpp.c (21885B)

---

 #include <assert.h>
 #include <ctype.h>
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
 
 #include <scc/cstd.h>
 #include <scc/scc.h>
 #include "cc1.h"
 
 struct ifstate {
 	unsigned char done;
 	unsigned char enabled;
 	unsigned char iselse;
 };
 
 static unsigned ncmdlines;
 static Symbol *symline, *symfile;
 static struct ifstate ifstate[NR_COND];
 static int cppoff;
 static struct items dirinclude;
 
 unsigned cppctx;
 int disexpand;
 int disescape;
 
 void
 defdefine(char *name, char *val, char *source)
 {
 	char buffer[INPUTSIZ+1];
 	char *def, *fmt = "#define %s %s\n";
 	Symbol *sym = &(Symbol) {
 		.name = name,
 		.flags = SDECLARED,
 	};
 
 	if (!val)
 		val = "";
 	if (strlen(fmt) + strlen(name) + strlen(val) > INPUTSIZ) {
 		errorp("macro definition '%s' too big", name);
 		return;
 	}
 
 	sprintf(buffer, fmt, name, val);
 	lineno = ++ncmdlines;
 
 	addinput(IPARAM, buffer, FAIL);
 	cpp();
 	delinput();
 }
 
 void
 undefmacro(char *s)
 {
 	killsym(lookup(NS_CPP, s, NOALLOC));
 }
 
 void
 icpp(void)
 {
 	struct tm *tm;
 	time_t t;
 	static char sdate[14], stime[11];
 	static struct {
 		char *name;
 		char *value;
 	} *bp, list[] = {
 		{"__STDC__", "1"},
 		{"__STDC_HOSTED__", "1"},
 		{"__SCC__", "1"},
 		{"__DATE__", sdate},
 		{"__TIME__", stime},
 		{"__STDC_VERSION__", STDC_VERSION},
 		{"__LINE__", NULL},
 		{"__FILE__", NULL},
 		{"__FLT_EVAL_METHOD__", "0"},
 		{NULL, NULL}
 	};
 
 	t = time(NULL);
 	tm = localtime(&t);
 	strftime(sdate, sizeof(sdate), "\"%b %d %Y\"", tm);
 	strftime(stime, sizeof(stime), "\"%H:%M:%S\"", tm);
 
 	for (bp = list; bp->name; ++bp)
 		defdefine(bp->name, bp->value, "built-in");
 
 	symline = lookup(NS_CPP, "__LINE__", ALLOC);
 	symfile = lookup(NS_CPP, "__FILE__", ALLOC);
 
 	ncmdlines = 0;
 }
 
 static char *
 appendpar(Macro *mp, char *s, int len)
 {
 	char *arg;
 	int siz = mp->argsiz;
 
 	if (len+1 > INT_MAX - siz) {
 		error("too long argument invoking macro \"%s\"",
 		      mp->sym->name);
 	}
 
 	mp->arg = xrealloc(mp->arg, siz + len + 1);
 	memcpy(mp->arg + siz, s, len);
 	mp->argsiz = siz += len;
 	mp->arg[siz] = '\0';
 }
 
 static void
 paren(Macro *mp)
 {
 	for (;;) {
 		switch (*input->p) {
 		case ')':
 			appendpar(mp, input->p++, 1);
 			return;
 		case '(':
 			appendpar(mp, input->p++, 1);
 			paren(mp);
 			break;
 		case '"':
 		case '\'':
 			next();
 			assert(yytoken == STRING || yytoken == CONSTANT);
 			appendpar(mp, yytext, yylen);
 			break;
 		case '\0':
 			if (!moreinput())
 				goto unterminated;
 			continue;
 		default:
 			appendpar(mp, input->p++, 1);
 			break;
 		}
 	}
 
 unterminated:
 	error("unterminated argument list invoking macro \"%s\"",
 	      mp->sym->name);
 }
 
 static char *
 parameter(Macro *mp)
 {
 	int siz;
 	char *s, *begin, *end;
 
 	mp->arg = NULL;
 	mp->argsiz = 0;
 
 	for (;;) {
 		switch (*input->p) {
 		case '"':
 		case '\'':
 			next();
 			assert(yytoken == STRING || yytoken == CONSTANT);
 			appendpar(mp, yytext, yylen);
 			break;
 		case '(':
 			appendpar(mp, input->p++, 1);
 			paren(mp);
 			break;
 		case ')':
 		case ',':
 			begin = mp->arg;
 			end = begin + mp->argsiz;
 
 			while (begin < end && isspace(*begin))
 				begin++;
 			while (end > begin && isspace(*end))
 				end--;
 
 			siz = end - begin;
 			s = memcpy(xmalloc(siz + 1), begin, siz);
 			s[siz] = '\0';
 
 			return s;
 		case '\0':
 			if (!moreinput())
 				goto unterminated;
 			continue;
 		default:
 			appendpar(mp, input->p++, 1);
 			break;
 		}
 	}
 
 unterminated:
 	error("unterminated argument list invoking macro \"%s\"",
 	      mp->sym->name);
 }
 
 static int
 parsepars(Macro *mp)
 {
 	int c, n;
 	char *name;
 
 	if (mp->npars == -1)
 		return 1;
 	if (ahead() != '(')
 		return 0;
 
 	input->p++;
 	name = mp->sym->name;
 
 	if (mp->npars == 0 && ahead() == ')') {
 		input->p++;
 		return 1;
 	}
 
 	disexpand = 1;
 	for (n = 0; n < NR_MACROARG; ++n) {
 		mp->arglist = xrealloc(mp->arglist, (n+1)*sizeof(char *));
 		mp->arglist[n] = parameter(mp);
 		DBG("MACRO fetched arg '%s'", mp->arglist[n]);
 
 		c = *input->p++;
 		if (c == ')')
 			break;
 		if (c != ',')
 			error("incorrect macro function-alike invocation of \"%s\"", name);
 	}
 	disexpand = 0;
 
 checknpars:
 	if (n+1 == mp->npars)
 		return 1;
 	error("macro \"%s\" received %d arguments, but it takes %d",
 	      mp->sym->name, n, mp->npars);
 }
 
 static int
 concatoper(char *def, char *cur)
 {
 	char *s;
 
 	for (s = cur + 4; isspace(*s); ++s)
 		;
 	if (*s == CONCAT)
 		return 1;
 
 	for (s = cur; s > def && isspace(s[-1]); --s)
 		;
 	if (s > def && s[-1] == CONCAT)
 		return 1;
 
 	return 0;
 }
 
 static int
 expandarg(char *arg, char *def, char *curdef, char *buf, int bufsiz)
 {
 	int siz;
 	char *s = buf;
 
 	/* gives priority to concatenation operators */
 	if (concatoper(def, curdef)) {
 		siz = strlen(arg);
 		if (siz >= bufsiz) {
 			siz = -1;
 		} else {
 			memcpy(buf, arg, siz);
 			buf += siz;
 		}
 	} else {
 		addinput(IPARAM, arg, FAIL);
 		for (siz = 0; next() != EOFTOK; siz += yylen+1) {
 			if (yylen > bufsiz-2) {
 				siz = -1;
 				break;
 			}
 			memcpy(buf, yytext, yylen);
 			bufsiz -= yylen + 1;
 			buf += yylen;
 			*buf++ = ' ';
 		}
 
 		delinput();
 	}
 	*buf = '\0';
 
 	DBG("MACRO parameter '%s' expanded to '%s'", arg, s);
 
 	return siz;
 }
 
 static int
 copymacro(Macro *mp)
 {
 	int delim, c, esc;
 	char *s, *p, *arg, *bp;
 	int size, bufsiz;
 
 	if (mp->sym == symfile)
 		return sprintf(mp->buffer, "\"%s\" ", filenam);
 	if (mp->sym == symline)
 		return sprintf(mp->buffer, "%d ", lineno);
 
 	bp = mp->buffer;
 	bufsiz = mp->bufsiz;
 	for (s = mp->def; c = *s; ++s) {
 		switch (c) {
 		case '\'':
 			delim = '\'';
 			goto search_delim;
 		case '\"':
 			delim = '"';
 		search_delim:
 			esc = 0;
 			p = s;
 			for (++s; c = *s; ++s) {
 				if (c == '\\' && !esc)
 					esc = 1;
 				else if (c == delim &&!esc)
 					break;
 				else
 					esc = 0;
 			}
 			size = s - p + 1;
 			if (size > bufsiz)
 				goto expansion_too_long;
 			memcpy(bp, p, size);
 			bufsiz -= size;
 			bp += size;
 			break;
 		case CONCAT:
 			/* token concatenation operator */
 			DBG("MACRO concat");
 			while (bp[-1] == ' ')
 				--bp, ++bufsiz;
 			while (s[1] == ' ')
 				++s;
 			break;
 		case STRINGIZE:
 			/* stringfier operator */
 			DBG("MACRO stringize");
 			arg = mp->arglist[atoi(s += 2)];
 			s += 2;
 
 			if (bufsiz < 3)
 				goto expansion_too_long;
 
 			*bp++ = '"';
 			while ((c = *arg++) != '\0') {
 				if (c == '"') {
 					if (bufsiz < 3)
 						goto expansion_too_long;
 					*bp++ = '\\';
 					*bp++ = '"';
 					bufsiz -= 2;
 				} else {
 					if (bufsiz < 2)
 						goto expansion_too_long;
 					*bp++ = c;
 					bufsiz--;
 				}
 			}
 			*bp++ = '"';
 
 			break;
 		case MACROPAR:
 			/* parameter substitution */
 			arg = mp->arglist[atoi(s+1)];
 			size = expandarg(arg, mp->def, s, bp, bufsiz);
 			if (size < 0)
 				goto expansion_too_long;
 			bp += size;
 			bufsiz -= size;
 			s += 3;
 			break;
 		default:
 			if (bufsiz-- == 0)
 				goto expansion_too_long;
 			*bp++ = c;
 			break;
 		}
 	}
 	*bp = '\0';
 
 	return bp - mp->buffer;
 
 expansion_too_long:
 	error("macro expansion of \"%s\" too long", mp->sym->name);
 }
 
 static void
 addhideset(Input *ip,  Symbol *sym)
 {
 	Symbol **set;
 	Symbol **p;
 
 	set = ip->macro->hideset;
 	for (p = set; p < &set[NR_MACROARG] && *p; ++p) {
 		if (*p == sym)
 			return;
 	}
 
 	if (p == &set[NR_MACROARG])
 		error("too complex macro expansion");
 
 	*p = sym;
 	DBG("MACRO Adding %s to hideset of %s",
 	    sym->name, ip->macro->sym->name);
 }
 
 static void
 hide(Symbol *sym)
 {
 	DBG("SYM: hidding symbol %s %d", sym->name, sym->hide);
 	sym->hide = 1;
 }
 
 static void
 unhide(Symbol *sym)
 {
 	DBG("SYM: unhidding symbol %s %d", sym->name, sym->hide);
 	sym->hide = 0;
 }
 
 void
 delmacro(Macro *mp)
 {
 	int i;
 	Symbol **p;
 
 	if (!mp)
 		return;
 
 	if (mp->arglist) {
 		for (i = 0; i < mp->npars; i++)
 			free(mp->arglist[i]);
 	}
 
 	for (p = mp->hideset; p < &mp->hideset[NR_MACROARG] && *p; ++p)
 		unhide(*p);
 
 	free(mp->arglist);
 	free(mp);
 }
 
 Macro *
 newmacro(Symbol *sym)
 {
 	Macro *mp;
 
 	mp = xmalloc(sizeof(*mp));
 	*mp = (Macro) {0};
 	mp->sym = sym;
 	mp->def = sym->u.s + 3;
 	if (sym->u.s)
 		mp->npars = atoi(sym->u.s);
 
 	return mp;
 }
 
 int
 expand(Symbol *sym)
 {
 	int siz;
 	Macro *mp;
 	Input *ip;
 	Symbol **p;
 
 	DBG("MACRO '%s' detected disexpand=%d hide=%d",
 	    sym->name, disexpand, sym->hide);
 
 	if (disexpand || sym->hide || sym->token != IDEN)
 		return 0;
 
 	mp = newmacro(sym);
 	mp->fname = filenam;
 
 	if (!parsepars(mp)) {
 		delmacro(mp);
 		return 0;
 	}
 
 	addinput(IMACRO, mp, FAIL);
 	mp->buffer = input->line;
 	mp->bufsiz = INPUTSIZ-1;
 
 	siz = copymacro(mp);
 	mp->buffer[siz] = '\0';
 
 	for (ip = input; ip; ip = ip->next) {
                 if ((ip->flags & ITYPE) == IMACRO)
 			addhideset(ip, sym);
 	}
 
 	for (p = mp->hideset; p < &mp->hideset[NR_MACROARG] && *p; ++p)
 		hide(*p);
 
 	DBG("MACRO '%s' expanded to :'%s'", mp->sym->name, mp->buffer);
 
 	return 1;
 }
 
 static int
 getpars(Symbol *args[NR_MACROARG])
 {
 	int n, c;
 	Symbol *sym;
 
 	if (*input->p != '(')
 		return -1;
 
 	/* skip the '(' */
 	next();
 	next();
 	if (yytoken == ')')
 		return 0;
 
 	n = 0;
 	do {
 		if (n == NR_MACROARG) {
 			cpperror("too many parameters in macro");
 			return NR_MACROARG;
 		}
 		if (accept(ELLIPSIS)) {
 			args[n++] = NULL;
 			break;
 		}
 		if (yytoken != IDEN) {
 			cpperror("macro arguments must be identifiers");
 			return NR_MACROARG;
 		}
 		if ((sym = install(NS_IDEN, yylval.sym)) == NULL) {
 			errorp("duplicated macro parameter '%s'", yytext);
 		} else {
 			sym->flags |= SUSED;
 			args[n++] = sym;
 		}
 		next();
 	} while (accept(','));
 
 	if (yytoken != ')') {
 		cpperror("expected ')' at the end of macro argument list");
 		return NR_MACROARG;
 	}
 
 	return n;
 }
 
 static int
 getdefs(Symbol *args[NR_MACROARG], int nargs, char *buffer, size_t bufsiz)
 {
 	size_t len;
 	char *bp, *p;
 	Symbol **argp, *sym;
 	int c, id, token, prevc, ispar;
 
 	while (isspace(*input->p))
 		++input->p;
 
 	bp = buffer;
 	for (prevc = 0; (c = *input->p) != '\n' && c != '\0'; ++input->p) {
 		len = 1;
 		ispar = 0;
 		token = c;
 		sym = NULL;
 
 		if (c == '#') {
 			if (input->p[1] == '#') {
 				token = CONCAT;
 				++input->p;
 			} else {
 				token = STRINGIZE;
 			}
 		} else if (c == '_' || isalpha(c)) {
 			token = IDEN;
 			for (p = input->p; isalnum(*p) || *p == '_'; ++p)
 				;
 			len = p - input->p;
 			if (len >  INTIDENTSIZ) {
 				cpperror("identifier too long in macro definition");
 				return 0;
 			}
 			memcpy(yytext, input->p, len);
 			yytext[len] = '\0';
 			yylen = len;
 			input->p = p - 1;
 			sym = lookup(NS_IDEN, yytext, NOALLOC);
 		} else if (c == '"' || c == '\'') {
 			next();
 			assert(yytoken == STRING || yytoken == CONSTANT);
 			token = yytoken;
 			len = yylen;
 		}
 
 		if (sym && nargs > 0) {
 			for (argp = args; argp < &args[nargs]; ++argp) {
 				if (*argp == sym)
 					break;
 			}
 			if (argp != &args[nargs]) {
 				id = argp - args;
 				sprintf(yytext,
 					"%c%02d%c", MACROPAR, id, MACROPAR);
 				ispar = 1;
 				yylen = len = 4;
 			}
 		}
 
 		if (prevc == 0 && token == CONCAT)
 			goto wrong_concat;
 
 		if (prevc == STRINGIZE && !ispar) {
 			cpperror("'#' is not followed by a macro parameter");
 			return 0;
 		}
 
 		if (len >= bufsiz) {
 			cpperror("macro too long");
 			return 0;
 		}
 
 		if (token == IDEN || token == STRING || token == CONSTANT)
 			memcpy(bp, yytext, yylen);
 		else
 			*bp = token;
 
 		bp += len;
 		bufsiz -= len;
 		prevc = token;
 	}
 
 end_loop:
 	if ((yytoken = c) == '\0')
 		yytoken = EOFTOK;
 	if (prevc == CONCAT)
 		goto wrong_concat;
 	for ( ; bp > buffer && isspace(bp[-1]); --bp);
 		;
 	*bp = '\0';
 	return 1;
 
 wrong_concat:
 	cpperror("'##' cannot appear at either ends of a macro expansion");
 	return 0;
 }
 
 static void
 define(void)
 {
 	Symbol *sym,*args[NR_MACROARG];
 	char buff[LINESIZ+1];
 	int n;
 
 	if (cppoff)
 		return;
 
 	disescape = 1;
 	namespace = NS_CPP;
 	next();
 
 	if (yytoken != IDEN) {
 		cpperror("macro names must be identifiers");
 		return;
 	}
 	sym = yylval.sym;
 
 	namespace = NS_IDEN;       /* Avoid polution in NS_CPP */
 	if ((n = getpars(args)) == NR_MACROARG)
 		goto delete;
 	if (n > 0 && !args[n-1])  /* it is a variadic function */
 		--n;
 
 	sprintf(buff, "%02d#", n);
 	if (!getdefs(args, n, buff+3, LINESIZ-3))
 		goto delete;
 
 	if (sym->flags & SDECLARED) {
 		if (strcmp(sym->u.s, buff) != 0)
 			warn("'%s' redefined", sym->name);
 		free(sym->u.s);
 	} else {
 		sym = install(NS_CPP, sym);
 		sym->flags |= SDECLARED|SSTRING;
 	}
 
 	sym->u.s = xstrdup(buff);
 	DBG("MACRO '%s' defined as '%s'", sym->name, buff);
 	return;
 
 delete:
 	killsym(sym);
 }
 
 void
 incdir(char *dir)
 {
 	if (!dir || *dir == '\0')
 		die("cc1: incorrect -I flag");
 	newitem(&dirinclude, dir);
 }
 
 static int
 includefile(char *dir, char *file, size_t filelen)
 {
 	size_t dirlen;
 	char path[FILENAME_MAX];
 
 	if (!dir) {
 		dirlen = 0;
 		if (filelen > FILENAME_MAX-1)
 			return 0;
 	} else {
 		dirlen = strlen(dir);
 		if (dirlen + filelen > FILENAME_MAX-2)
 			return 0;
 		memcpy(path, dir, dirlen);
 		if (dir[dirlen-1] != '/')
 			path[dirlen++] = '/';
 	}
 	memcpy(path+dirlen, file, filelen);
 	path[dirlen + filelen] = '\0';
 
 	return addinput(IFILE, path, NOFAIL);
 }
 
 static char *
 cwd(char *buf)
 {
 	char *p, *s = filenam;
 	size_t len;
 
 	if ((p = strrchr(s, '/')) == NULL)
 		return NULL;
 	if ((len = p - s) >= FILENAME_MAX)
 		die("cc1: current work directory too long");
 	memcpy(buf, s, len);
 	buf[len] = '\0';
 	return buf;
 }
 
 static void
 include(void)
 {
 	char dir[FILENAME_MAX], file[FILENAME_MAX], *p, **bp;
 	size_t filelen;
 	int n;
 
 	if (cppoff)
 		return;
 
 	disexpand = 0;
 	namespace = NS_IDEN;
 	next();
 
 	switch (*yytext) {
 	case '<':
 		if ((p = strchr(input->begin, '>')) == NULL || p[-1] == '<')
 			goto bad_include;
 		filelen = p - input->begin;
 		if (filelen >= FILENAME_MAX)
 			goto too_long;
 		memcpy(file, input->begin, filelen);
 		file[filelen] = '\0';
 
 		input->begin = input->p = p+1;
 		if (next() != '\n')
 			goto trailing_characters;
 
 		break;
 	case '"':
 		if (yylen < 3)
 			goto bad_include;
 		filelen = yylen-2;
 		if (filelen >= FILENAME_MAX)
 			goto too_long;
 		memcpy(file, yytext+1, filelen);
 		file[filelen] = '\0';
 
 		if (next() != '\n')
 			goto trailing_characters;
 
 		if (includefile(cwd(dir), file, filelen))
 			goto its_done;
 		break;
 	default:
 		goto bad_include;
 	}
 
 	n = dirinclude.n;
 	for (bp = dirinclude.s; n--; ++bp) {
 		if (includefile(*bp, file, filelen))
 			goto its_done;
 	}
 	cpperror("included file '%s' not found", file);
 
 its_done:
 	return;
 
 trailing_characters:
 	cpperror("trailing characters after preprocessor directive");
 	return;
 
 too_long:
 	cpperror("too long file name in #include");
 	return;
 
 bad_include:
 	cpperror("#include expects \"FILENAME\" or <FILENAME>");
 	return;
 }
 
 static void
 line(void)
 {
 	long n;
 	char *endp, *fname;
 
 	if (cppoff)
 		return;
 
 	disexpand = 0;
 	next();
 	n = strtol(yytext, &endp, 10);
 	if (n <= 0 || n > USHRT_MAX || *endp != '\0') {
 		cpperror("first parameter of #line is not a positive integer");
 		return;
 	}
 
 	next();
 	if (yytoken == '\n') {
 		fname = NULL;
 	} else {
 		if (*yytext != '\"' || yylen == 1) {
 			cpperror("second parameter of #line is not a valid filename");
 			return;
 		}
 		fname = yylval.sym->u.s;
 	}
 	setloc(fname, n - 1);
 	if (yytoken != '\n')
 		next();
 }
 
 static void
 pragma(void)
 {
 	if (cppoff)
 		return;
 	next();
 	warn("ignoring pragma '%s'", yytext);
 	*input->p = '\0';
 	next();
 }
 
 static void
 usererr(void)
 {
 	if (cppoff)
 		return;
 	cpperror("#error %s", input->p);
 	exit(EXIT_FAILURE);
 	next();
 }
 
 
 Node *
 defined(void)
 {
 	Symbol *sym;
 	int paren;
 
 	disexpand = 1;
 	next();
 	paren = accept('(');
 	if (yytoken != IDEN && yytoken != TYPEIDEN)
 		cpperror("operator 'defined' requires an identifier");
 	if (yytoken == TYPEIDEN || !(yylval.sym->flags & SDECLARED))
 		sym = zero;
 	else
 		sym = one;
 	disexpand = 0;
 	next();
 	if (paren)
 		expect(')');
 	return constnode(sym);
 }
 
 static void
 ifclause(int negate, int isifdef)
 {
 	Symbol *sym;
 	unsigned n;
 	int enabled, done;
 	Node *expr;
 
 	if (cppctx == NR_COND-1)
 		error("too many nesting levels of conditional inclusion");
 	n = cppctx++;
 	DBG("CPP ifclause updates cppctx=%d", cppctx);
 
 	if (n > 0 && !ifstate[n-1].enabled) {
 		done = 1;
 		enabled = 0;
 		goto disabled;
 	}
 
 	namespace = NS_CPP;
 	next();
 
 	if (isifdef) {
 		if (yytoken != IDEN) {
 			cpperror("no macro name given in #%s directive",
 			         (negate) ? "ifndef" : "ifdef");
 			return;
 		}
 		sym = yylval.sym;
 		next();
 		enabled = (sym->flags & SDECLARED) != 0;
 		if (!enabled)
 			killsym(sym);
 	} else {
 		/* TODO: catch recovery here */
 		if ((expr = constexpr()) == NULL) {
 			cpperror("parameter of #if is not an integer constant expression");
 			return;
 		}
 		DBG("CPP if expr=%d", expr->sym->u.i);
 		enabled = expr->sym->u.i != 0;
 		freetree(expr);
 	}
 
 	if (negate)
 		enabled = !enabled;
 	done = enabled;
 
 disabled:
 	cppoff = !enabled;
 	DBG("CPP if result=%d", enabled);
 	ifstate[n].done = done;
 	ifstate[n].enabled = enabled;
 	ifstate[n].iselse = 0;
 }
 
 static void
 cppif(void)
 {
 	DBG("CPP line=%u if cppctx=%d", lineno, cppctx);
 	disexpand = 0;
 	ifclause(0, 0);
 }
 
 static void
 ifdef(void)
 {
 	DBG("CPP line=%u ifdef cppctx=%d", lineno, cppctx);
 	ifclause(0, 1);
 }
 
 static void
 ifndef(void)
 {
 	DBG("CPP line=%u ifndef cppctx=%d", lineno, cppctx);
 	ifclause(1, 1);
 }
 
 static void
 cppelse(void)
 {
 	DBG("CPP line=%u else cppctx=%d", lineno, cppctx);
 
 	if (cppctx == 0 || ifstate[cppctx-1].iselse) {
 		cpperror("#else without #ifdef/ifndef");
 		return;
 	}
 
 	/*
 	 * If we are disabled by a upper ifdef then ifclause() already
 	 * marked us as disabled and done. So if we are done then we
 	 * disable cpp because or ifclause was true, or it was disabled
 	 * by the upper. If we are not done, then it is our turn.
 	 */
 	if (ifstate[cppctx-1].done) {
 		ifstate[cppctx-1].enabled = 0;
 		cppoff = 1;
 	} else {
 		ifstate[cppctx-1].done = 1;
 		ifstate[cppctx-1].enabled = 1;
 		cppoff = 0;
 	}
 	ifstate[cppctx-1].iselse = 1;
 
 	next();
 }
 
 static void
 elif(void)
 {
 	DBG("CPP line=%u elif cppctx=%d", lineno, cppctx);
 
 	if (cppctx == 0 || ifstate[cppctx-1].iselse) {
 		cpperror("#elif without #ifdef/ifndef");
 		return;
 	}
 
 	/*
 	 * If we are disabled by a upper ifdef then ifclause() already
 	 * marked us as disabled and done. So if we are done then we
 	 * disable cpp because or ifclause was true, or it was disabled
 	 * by the upper. If we are not done, then we have to evaluate
 	 * the if condition.
 	 */
 	if (ifstate[cppctx-1].done) {
 		ifstate[cppctx-1].enabled = 0;
 		cppoff = 1;
 	} else {
 		--cppctx;
 		DBG("elif updates cppctx=%d", cppctx);
 		cppif();
 	}
 }
 
 static void
 endif(void)
 {
 	DBG("CPP line=%u endif cppctx=%d", lineno, cppctx);
 
 	if (cppctx == 0)
 		error("#endif without #if");
 
 	if (cppctx > 1)
 		cppoff = !ifstate[cppctx - 2].enabled;
 	else
 		cppoff = 0;
 
 	--cppctx;
 	DBG("CPP endif updates cppctx=%d", cppctx);
 	next();
 }
 
 static void
 undef(void)
 {
 	if (cppoff)
 		return;
 
 	namespace = NS_CPP;
 	next();
 	if (yytoken != IDEN) {
 		error("no macro name given in #undef directive");
 		return;
 	}
 	killsym(yylval.sym);
 	next();
 }
 
 int
 cpp(void)
 {
 	static struct {
 		unsigned char token;
 		void (*fun)(void);
 	} *bp, clauses [] = {
 		{DEFINE, define},
 		{INCLUDE, include},
 		{LINE, line},
 		{IFDEF, ifdef},
 		{IF, cppif},
 		{ELIF, elif},
 		{IFNDEF, ifndef},
 		{ELSE, cppelse},
 		{ENDIF, endif},
 		{UNDEF, undef},
 		{PRAGMA, pragma},
 		{ERROR, usererr},
 		{0, NULL}
 	};
 	int ns;
 	char *p;
 
 	for (p = input->p; isspace(*p); ++p)
 		;
 
 	if (*p != '#') {
 		if (cppoff)
 			*input->p = '\0';
 		return cppoff;
 	}
 	input->p = p+1;
 
 	disexpand = 1;
 	lexmode = CPPMODE;
 	ns = namespace;
 	namespace = NS_CPPCLAUSES;
 	next();
 	namespace = NS_IDEN;
 
 	if (yytoken == '\n')
 		goto ret;
 
 	for (bp = clauses; bp->token && bp->token != yytoken; ++bp)
 		;
 	if (!bp->token) {
 		errorp("incorrect preprocessor directive '%s'", yytext);
 		goto ret;
 	}
 
 	DBG("CPP %s", yytext);
 
 	/*
 	 * create a new context to avoid polish the current context,
 	 * and to get all the symbols freed at the end
 	 */
 	pushctx();
 	(*bp->fun)();
 	popctx();
 
 	/*
 	 * #include changes the content of input->line, so the correctness
 	 * of the line must be checked in the own include(), and we have
 	 * to skip this tests. For the same reason include() is the only
 	 * function which does not prepare the next token
 	 */
 	if (bp->token == INCLUDE)
 		goto ret;
 
 	if (yytoken != '\n' && yytoken != EOFTOK && !cppoff)
 		cpperror("trailing characters after preprocessor directive");
 
 ret:
 	disescape = 0;
 	disexpand = 0;
 	lexmode = CCMODE;
 	namespace = ns;
 
 	/*
 	 * at this point we know that the cpp line is processed, and any error
 	 * is generated but as next is called we cannot be sure that input is
 	 * valid anymore, but in case of begin valid we want to discard any
 	 * pending input in the current line
 	 */
 	if (input)
 		*input->p = '\0';
 
 	return 1;
 }
 
 void
 ppragmaln(void)
 {
 	static char file[FILENAME_MAX];
 	static unsigned nline;
 	char *s;
 
 	putchar('\n');
 	if (strcmp(file, filenam)) {
 		strcpy(file, filenam);
 		s = "#line %u \"%s\"\n";
 	} else if (nline+1 != lineno) {
 		s = "#line %u\n";
 	} else {
 		s = "";
 	}
 	nline = lineno;
 	printf(s, nline, file);
 }
 
 void
 outcpp(void)
 {
 	int c;
 	char *s, *t;
 
 	for (next(); yytoken != EOFTOK; next()) {
 		if (onlyheader)
 			continue;
 		if (yytoken != STRING) {
 			printf("%s ", yytext);
 			continue;
 		}
 		for (s = yytext; (c = *s) != '\0'; ++s) {
 			switch (c) {
 			case '\n':
 				t = "\\n";
 				goto print_str;
 			case '\v':
 				t = "\\v";
 				goto print_str;
 			case '\b':
 				t = "\\b";
 				goto print_str;
 			case '\t':
 				t = "\\t";
 				goto print_str;
 			case '\a':
 				t = "\\a";
 				goto print_str;
 			case '\f':
 				t = "\\f";
 				goto print_str;
 			case '\r':
 				t = "\\r";
 				goto print_str;
 			case '"':
 				if (s == yytext || s[1] == '\0')
 					goto print_chr;
 				t = "\\\"";
 				goto print_str;
 			case '\'':
 				t = "\\'";
 				goto print_str;
 			case '\?':
 				t = "\\\?";
 				goto print_str;
 			case '\\':
 				putchar('\\');
 			default:
 			print_chr:
 				if (!isprint(c))
 					printf("\\x%x", c);
 				else
 					putchar(c);
 				break;
 			print_str:
 				fputs(t, stdout);
 				break;
 			}
 		}
 		putchar(' ');
 	}
 	putchar('\n');
 }