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Fix conditional inclusion

The previous implementation was obscure and it has failures.
It was due to the fact that the disabled lines were skipped in
the own preprocessor code, and it made hard to handle #else.
The solution, of course, is to handle them in morelines.

--- a/cc1/cc1.h

+++ b/cc1/cc1.h

@@ -300,6 +300,7 @@

 extern char yytext[];

 extern unsigned yytoken;

 extern unsigned short yylen;

+extern int cppoff;

 extern Type *voidtype, *pvoidtype, *booltype,	

             *uchartype,   *chartype,

--- a/cc1/cpp.c

+++ b/cc1/cpp.c

@@ -14,9 +14,11 @@

 static char *argp;

 static unsigned arglen;

-static unsigned numif, iffalse;

+static unsigned numif;

 static Symbol *lastmacro;

+unsigned char ifstatus[NR_COND];

+

 static bool

 iden(char **str)

 {

@@ -245,7 +247,7 @@

 	return s;

 }

 /*

- * Copy a define string, and substitute formal arguments of the

+ * Copy a string define, and substitute formal arguments of the

  * macro into strings in the form @XX@, where XX is the position

  * of the argument in the argument list.

  */

@@ -313,8 +315,10 @@

 	char *t;

 	Symbol *sym;

+	if (cppoff)

+		return 1;

 	if (!iden(&s))

-		error("macro names must be identifiers");

+		error("#define must have an identifier as parameter");

 	sym = lookup(NS_CPP);

 	if ((sym->flags & ISDEFINED) && sym->ns == NS_CPP) {

@@ -335,6 +339,8 @@

 {

 	char delim, c, *p, *file;

+	if (cppoff)

+		return 1;

 	if ((c = *s++) == '>')

 		delim = '>';

 	else if (c == '"')

@@ -361,6 +367,8 @@

 	char *file;

 	long n;

+	if (cppoff)

+		return 1;

 	if ((n = strtol(s, &s, 10)) <= 0 || n > USHRT_MAX)

 		error("first parameter of #line is not a positive integer");

@@ -388,6 +396,8 @@

 static bool

 pragma(char *s)

 {

+	if (cppoff)

+		return 1;

 	return 1;

 }

@@ -394,6 +404,8 @@

 static bool

 usererr(char *s)

 {

+	if (cppoff)

+		return 1;

 	error("#error %s", s);

 }

@@ -400,27 +412,20 @@

 static bool

 ifclause(char *s, int isdef)

 {

-	unsigned curif;

-	char *endp;

 	Symbol *sym;

+	unsigned n = numif++;

-	if (iden(&s))

-		error("...");

+	if (numif == NR_COND-1)

+		error("too much nesting levels of conditional inclusion");

+

+	if (!iden(&s))

+		error("#ifdef clause must have an identifier as parameter");

 	cleanup(s);

-	++numif;

-	if (iffalse == 0) {

-		sym = lookup(NS_CPP);

-		if ((sym->flags & ISDEFINED) != 0 == isdef)

-			return 1;

-	}

+	sym = lookup(NS_CPP);

+	if (!(ifstatus[n] = (sym->flags & ISDEFINED) != 0 == isdef))

+		++cppoff;

-	curif = iffalse++;

-	while (curif != iffalse) {

-		if (!moreinput())

-			error("found EOF while ...");

-	}

-

 	return 1;

 }

@@ -439,32 +444,25 @@

 static bool

 endif(char *s)

 {

-	cleanup(s);

 	if (numif == 0)

 		error("#endif without #if");

-	--numif;

-	return iffalse == 0;

+	cleanup(s);

+	if (!ifstatus[--numif])

+		--cppoff;

+	return 1;

 }

 static bool

 elseclause(char *s)

 {

-	unsigned curif;

+	struct ifstatus *ip;

-	cleanup(s);

 	if (numif == 0)

 		error("#else without #if");

+	cleanup(s);

+	cppoff += (ifstatus[numif-1] ^= 1) ? -1 : 1;

-	if (iffalse == 0) {

-		curif = iffalse++;

-		while (curif != iffalse) {

-			if (!moreinput())

-				error("found EOF while ...");

-		}

-	}

-	--iffalse;

-

-	return iffalse != 0;

+	return 1;

 }

 bool

--- a/cc1/lex.c

+++ b/cc1/lex.c

@@ -26,6 +26,7 @@

 struct yystype yylval;

 char yytext[IDENTSIZ + 1];

 unsigned short yylen;

+int cppoff;

 static unsigned lex_ns = NS_IDEN;

 static int safe, eof, incomment;

@@ -204,7 +205,7 @@

 	readline();

 	while (isspace(*p))

 		++p;

-	if (*p == '\0' || preprocessor(p))

+	if (*p == '\0' || preprocessor(p) || cppoff)

 		goto repeat;

 	input->p = input->begin = p;

 	return 1;