1 files changed, 12 insertions, 8 deletions

diff --git a/src/types.cpp b/src/types.cpp
index 9ffd10ca8..861841b59 100644
--- a/src/types.cpp
+++ b/src/types.cpp
@@ -152,10 +152,11 @@ struct TypeStruct {
 
 	bool            is_polymorphic;
 	bool            are_offsets_set             : 1;
-	bool            are_offsets_being_processed : 1;
 	bool            is_packed                   : 1;
 	bool            is_raw_union                : 1;
 	bool            is_poly_specialized         : 1;
+
+	std::atomic<bool> are_offsets_being_processed;
 };
 
 struct TypeUnion {
@@ -4099,18 +4100,18 @@ gb_internal bool type_set_offsets(Type *t) {
 	if (t->kind == Type_Struct) {
 		MUTEX_GUARD(&t->Struct.offset_mutex);
 		if (!t->Struct.are_offsets_set) {
-			t->Struct.are_offsets_being_processed = true;
+			t->Struct.are_offsets_being_processed.store(true);
 			t->Struct.offsets = type_set_offsets_of(t->Struct.fields, t->Struct.is_packed, t->Struct.is_raw_union, t->Struct.custom_min_field_align, t->Struct.custom_max_field_align);
-			t->Struct.are_offsets_being_processed = false;
+			t->Struct.are_offsets_being_processed.store(false);
 			t->Struct.are_offsets_set = true;
 			return true;
 		}
 	} else if (is_type_tuple(t)) {
 		MUTEX_GUARD(&t->Tuple.mutex);
 		if (!t->Tuple.are_offsets_set) {
-			t->Tuple.are_offsets_being_processed = true;
+			t->Tuple.are_offsets_being_processed.store(true);
 			t->Tuple.offsets = type_set_offsets_of(t->Tuple.variables, t->Tuple.is_packed, false, 1, 0);
-			t->Tuple.are_offsets_being_processed = false;
+			t->Tuple.are_offsets_being_processed.store(false);
 			t->Tuple.are_offsets_set = true;
 			return true;
 		}
@@ -4293,9 +4294,12 @@ gb_internal i64 type_size_of_internal(Type *t, TypePath *path) {
 			if (path->failure) {
 				return FAILURE_SIZE;
 			}
-			if (t->Struct.are_offsets_being_processed && t->Struct.offsets == nullptr) {
-				type_path_print_illegal_cycle(path, path->path.count-1);
-				return FAILURE_SIZE;
+			{
+				MUTEX_GUARD(&t->Struct.offset_mutex);
+				if (t->Struct.are_offsets_being_processed.load() && t->Struct.offsets == nullptr) {
+					type_path_print_illegal_cycle(path, path->path.count-1);
+					return FAILURE_SIZE;
+				}
 			}
 			type_set_offsets(t);
 			GB_ASSERT(t->Struct.fields.count == 0 || t->Struct.offsets != nullptr);