stmt: Allow labels intermixed with declarations in compound statements

C23 relaxes the restriction that labels must always be followed by
statements in N2508[0].

[0] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2508.pdf

1 files changed, 46 insertions, 38 deletions

diff --git a/stmt.c b/stmt.c
index 3bb09cf..9ae0039 100644
--- a/stmt.c
+++ b/stmt.c
@@ -7,49 +7,25 @@
 #include "util.h"
 #include "cc.h"
 
+/* 6.8.1 Labeled statements */
 static bool
-gotolabel(struct func *f)
+label(struct func *f, struct scope *s)
 {
 	char *name;
 	struct gotolabel *g;
-
-	if (tok.kind != TIDENT)
-		return false;
-	name = tok.lit;
-	if (!peek(TCOLON))
-		return false;
-	g = funcgoto(f, name);
-	g->defined = true;
-	funclabel(f, g->label);
-	return true;
-}
-
-/* 6.8 Statements and blocks */
-void
-stmt(struct func *f, struct scope *s)
-{
-	char *name;
-	struct expr *e;
-	struct type *t;
-	struct value *v;
-	struct block *b[4];
-	struct switchcases swtch;
+	struct block *b;
 	uint64_t i;
 
-	while (gotolabel(f))
-		;
 	switch (tok.kind) {
-	/* 6.8.1 Labeled statements */
 	case TCASE:
 		next();
 		if (!s->switchcases)
 			error(&tok.loc, "'case' label must be in switch");
-		b[0] = mkblock("switch_case");
-		funclabel(f, b[0]);
+		b = mkblock("switch_case");
+		funclabel(f, b);
 		i = intconstexpr(s, true);
-		switchcase(s->switchcases, i, b[0]);
+		switchcase(s->switchcases, i, b);
 		expect(TCOLON, "after case expression");
-		stmt(f, s);
 		break;
 	case TDEFAULT:
 		next();
@@ -60,15 +36,47 @@ stmt(struct func *f, struct scope *s)
 		expect(TCOLON, "after 'default'");
 		s->switchcases->defaultlabel = mkblock("switch_default");
 		funclabel(f, s->switchcases->defaultlabel);
-		stmt(f, s);
 		break;
+	case TIDENT:
+		name = tok.lit;
+		if (!peek(TCOLON))
+			return false;
+		g = funcgoto(f, name);
+		g->defined = true;
+		funclabel(f, g->label);
+		break;
+	default:
+		return false;
+	}
+	return true;
+}
+
+static void
+labelstmt(struct func *f, struct scope *s)
+{
+	while (label(f, s))
+		;
+	stmt(f, s);
+}
+
+/* 6.8 Statements and blocks */
+void
+stmt(struct func *f, struct scope *s)
+{
+	char *name;
+	struct expr *e;
+	struct type *t;
+	struct value *v;
+	struct block *b[4];
+	struct switchcases swtch;
 
+	switch (tok.kind) {
 	/* 6.8.2 Compound statement */
 	case TLBRACE:
 		next();
 		s = mkscope(s);
 		while (tok.kind != TRBRACE) {
-			if (gotolabel(f) || !decl(s, f))
+			if (!label(f, s) && !decl(s, f))
 				stmt(f, s);
 		}
 		s = delscope(s);
@@ -105,7 +113,7 @@ stmt(struct func *f, struct scope *s)
 
 		funclabel(f, b[0]);
 		s = mkscope(s);
-		stmt(f, s);
+		labelstmt(f, s);
 		s = delscope(s);
 
 		if (consume(TELSE)) {
@@ -113,7 +121,7 @@ stmt(struct func *f, struct scope *s)
 			funcjmp(f, b[2]);
 			funclabel(f, b[1]);
 			s = mkscope(s);
-			stmt(f, s);
+			labelstmt(f, s);
 			s = delscope(s);
 			funclabel(f, b[2]);
 		} else {
@@ -145,7 +153,7 @@ stmt(struct func *f, struct scope *s)
 		s = mkscope(s);
 		s->breaklabel = b[1];
 		s->switchcases = &swtch;
-		stmt(f, s);
+		labelstmt(f, s);
 		funcjmp(f, b[1]);
 
 		funclabel(f, b[0]);
@@ -178,7 +186,7 @@ stmt(struct func *f, struct scope *s)
 		s = mkscope(s);
 		s->continuelabel = b[0];
 		s->breaklabel = b[2];
-		stmt(f, s);
+		labelstmt(f, s);
 		s = delscope(s);
 		funcjmp(f, b[0]);
 		funclabel(f, b[2]);
@@ -196,7 +204,7 @@ stmt(struct func *f, struct scope *s)
 		s->continuelabel = b[1];
 		s->breaklabel = b[2];
 		funclabel(f, b[0]);
-		stmt(f, s);
+		labelstmt(f, s);
 		s = delscope(s);
 
 		expect(TWHILE, "after 'do' statement");
@@ -250,7 +258,7 @@ stmt(struct func *f, struct scope *s)
 		s = mkscope(s);
 		s->breaklabel = b[3];
 		s->continuelabel = b[2];
-		stmt(f, s);
+		labelstmt(f, s);
 		s = delscope(s);
 
 		funclabel(f, b[2]);