shithub: scc

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Detect when a label used in a goto is not defined

We cannot know that a goto label is not defined until the
end of a function, so the best place for this check is in
the free stage, where we can be sure that the label is
not going to be defined.

--- a/cc1.h

+++ b/cc1.h

@@ -100,6 +100,7 @@

 		bool isstatic : 1;

 		bool isauto : 1;

 		bool isregister : 1;

+		bool isdefined : 1;

 	} s;

 	union {

 		int i;

--- a/stmt.c

+++ b/stmt.c

@@ -12,14 +12,25 @@

 static void stmt(Symbol *lbreak, Symbol *lcont, Symbol *lswitch);

 static Symbol *

-label(char *s)

+label(char *s, char define)

 {

-	if (!s)

+	Symbol *sym;

+

+	if (s) {

+		if ((sym = lookup(s, NS_LABEL)) != NULL) {

+			if (define && sym->s.isdefined)

+				error("label '%s' already defined", s);

+			else

+				sym->s.isdefined = 1;

+			return sym;

+		}

+	} else {

 		s = "";

-	else if (lookup(s, NS_LABEL))

-		error("label '%s' already defined", s);

+	}

-	return install(s, NS_LABEL);

+	sym = install(s, NS_LABEL);

+	sym->s.isdefined = define;

+	return sym;

 }

 static void

@@ -45,9 +56,13 @@

 static void

 While(Symbol *lswitch)

 {

-	Symbol *begin= label(NULL), *cond = label(NULL), *end = label(NULL);

+	Symbol *begin, *cond, *end;

 	Node *np;

+	begin = label(NULL, 1);

+	end = label(NULL, 1);

+	cond = label(NULL, 1);

+

 	expect(WHILE);

 	np = condition();

 	emitjump(cond, NULL);

@@ -63,9 +78,13 @@

 static void

 For(Symbol *lswitch)

 {

-	Symbol *begin= label(NULL), *cond = label(NULL), *end = label(NULL);

+	Symbol *begin, *cond, *end;

 	Node *econd = NULL, *einc = NULL;

+	begin = label(NULL, 1);

+	end = label(NULL, 1);

+	cond = label(NULL, 1);

+

 	expect(FOR);

 	expect('(');

 	stmtexp();

@@ -92,7 +111,7 @@

 static void

 Dowhile(Symbol *lswitch)

 {

-	Symbol *begin= label(NULL), *end = label(NULL);

+	Symbol *begin= label(NULL, 1), *end = label(NULL, 1);

 	expect(DO);

@@ -137,7 +156,7 @@

 static void

 Label(void)

 {

-	emitlabel(label(yytext));

+	emitlabel(label(yytext, 1));

 	expect(IDEN);

 	expect(':');

@@ -160,7 +179,7 @@

 	if (yytoken != IDEN)

 		error("unexpected '%s'", yytext);

-	emitjump(label(yytext), NULL);

+	emitjump(label(yytext, 0), NULL);

 	next();

 	expect(';');

 }

--- a/symbol.c

+++ b/symbol.c

@@ -37,6 +37,8 @@

 	for (sym = tbl->head; sym; sym = next) {

 		if (sym->ctx <= curctx)

 			break;

+		if (ns == NS_LABEL && !sym->s.isdefined)

+			error("label '%s' is not defined", sym->name);

 		tbl->htab[hash(sym->name)] = sym->hash;

 		next = tbl->head = sym->next;

 		free(sym->name);