在Objective-C中初始化为类变量时,在哪种内存上分配C结构

struct MyStruct {
    int x;
    int y;
};

@implementation MyClass
{
    struct MyStruct *_myStruct;
}

- (instancetype)init {
    self = [super init];
    if (self) {
        _myStruct = (struct MyStruct *)malloc(sizeof(struct MyStruct));
        if (_myStruct == NULL) {
            NSLog(@"Memory allocation failed");
            return nil;
        }
        _myStruct->x = 10;
        _myStruct->y = 20;
    }
    return self;
}

- (void)dealloc {
    free(_myStruct);
}

@end

struct MyStruct {
    int x;
    int y;
};

@implementation MyClass
{
    struct MyStruct _myStruct;
}

- (instancetype)init {
    self = [super init];
    if (self) {
        _myStruct = (struct MyStruct *)alloca(sizeof(struct MyStruct));
        _myStruct->x = 10;
        _myStruct->y = 20;
    }
    return self;
}

@end