@:nativeGen interface use leads to crash

[tobil4sk]

When investigating HaxeFoundation/haxe#10427, I discovered that this program using native interfaces crashes:

@:nativeGen
interface IFirst {
        public function doFirst():Void;
}

@:nativeGen
interface ISecond {
        public function doSecond():Void;
}

class Main implements IFirst implements ISecond {
        public var data:Array<Int> = [1, 2, 3];

        public function new() {}

        public function doFirst() {
                trace(data);
        }

        public function doSecond() {
                trace(data);
        }

        static function main() {
                final obj = new Main();

                final interfaceRef:ISecond = obj;

                cpp.vm.Gc.run(true);

                interfaceRef.doSecond();
        }
}

Compiled on linux with:

haxe -m Main --cpp bin

This crashes while trying to join the Array because the ->length field has become garbage.