decl: Disallow members with incomplete types

Make an exception for flexible array members, though we should also
check that the flexible array member, if any, is last.

3 files changed, 32 insertions, 1 deletions

diff --git a/decl.c b/decl.c
index d9e2a85..8912c6a 100644
--- a/decl.c
+++ b/decl.c
@@ -685,7 +685,9 @@ addmember(struct structbuilder *b, struct qualtype mt, char *name, int align, ui
 	struct member *m;
 	size_t end;
 
-	// XXX: check incomplete type, except for flexible array member
+	/* XXX: flexible array member must be last */
+	if (mt.type->incomplete && mt.type->kind != TYPEARRAY)
+		error(&tok.loc, "struct member '%s' has incomplete type", name);
 	if (mt.type->kind == TYPEFUNC)
 		error(&tok.loc, "struct member '%s' has function type", name);
 	assert(mt.type->align > 0);
diff --git a/test/struct-flexible-array.c b/test/struct-flexible-array.c
new file mode 100644
index 0000000..57bd95a
--- /dev/null
+++ b/test/struct-flexible-array.c
@@ -0,0 +1,10 @@
+struct s {
+	int a;
+	short b[];
+};
+
+int x = sizeof(struct s);
+
+int f(struct s *s) {
+	return s->b[2];
+}
diff --git a/test/struct-flexible-array.qbe b/test/struct-flexible-array.qbe
new file mode 100644
index 0000000..535c5d2
--- /dev/null
+++ b/test/struct-flexible-array.qbe
@@ -0,0 +1,19 @@
+export data $x = align 4 { w 4, }
+export
+function w $f(l %.1) {
+@start.1
+	%.2 =l alloc8 8
+	storel %.1, %.2
+@body.2
+	%.3 =l loadl %.2
+	%.4 =l copy %.3
+	%.5 =l mul 4, 1
+	%.6 =l add %.4, %.5
+	%.7 =l copy %.6
+	%.8 =l extsw 2
+	%.9 =l mul %.8, 2
+	%.10 =l add %.7, %.9
+	%.11 =w loadsh %.10
+	%.12 =w extsh %.11
+	ret %.12
+}