通过C++从后台线程错误修改自动布局引擎

当我通过双向djinni架构从C++进行UI调用时，Xcode 7.1中出现以下错误：

This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes. This will cause an exception in a future release.

我能够用这里给出的解决方案解决Objective-C中的问题：

是否收到"此应用程序正在修改自动布局引擎"错误？

dispatch_async(dispatch_get_main_queue(), ^{
    // code here
});

我的问题是，有没有一种方法可以在C++中以某种方式实现这一点，而不必在每次调用UI时都在Objective-C中调用dispatch_async？或者，就Xcode而言，C++的每个调用都被视为后台线程吗？

发布省略了自动生成的源文件的相关代码，完整的项目也可以在github:上获得

cpptimer.djinni:

timer = interface +c {
    static create_with_listener(listener: timer_listener): timer;
    start_timer(seconds: i32);
}
timer_listener = interface +j +o {
    timer_ticked(seconds_remaining: i32);
    timer_ended();
}

timer_impl.hpp

#pragma once
#include <boost/asio.hpp>
#include "timer.hpp"
#include "timer_listener.hpp"
namespace cpptimer {
    class TimerImpl : public Timer {
    public:
        TimerImpl(const std::shared_ptr<TimerListener> & listener);
        void StartTimer(int32_t seconds);
    private:
        void TimerTick(const boost::system::error_code& e);
        std::shared_ptr<TimerListener> listener_;
        boost::asio::io_service io_service_;
        boost::asio::deadline_timer timer_;
        int time_remaining_;
    };
}

timer_impl.cpp

#include <boost/bind.hpp>
#include <boost/thread.hpp>
#include "timer_impl.hpp"
namespace cpptimer {
    std::shared_ptr<Timer> Timer::CreateWithListener(const std::shared_ptr<TimerListener> & listener) {
        return std::make_shared<TimerImpl>(listener);
    }
    TimerImpl::TimerImpl(const std::shared_ptr<TimerListener> & listener):
            io_service_(),
            timer_(io_service_, boost::posix_time::seconds(1)) {
        listener_ = listener;
    }
    void TimerImpl::StartTimer(int32_t seconds) {
        time_remaining_ = seconds;
        io_service_.reset();
        timer_.async_wait(boost::bind(&TimerImpl::TimerTick, this, boost::asio::placeholders::error));
        boost::thread th([&] { io_service_.run(); });
    }
    void TimerImpl::TimerTick(const boost::system::error_code& e) {
        if(e != boost::asio::error::operation_aborted) {
            time_remaining_--;
            std:: cout << "C++: TimerTick() with " << std::to_string(time_remaining_) << " seconds remaining.n";
            if (time_remaining_ > 0) {
                timer_.expires_from_now(boost::posix_time::seconds(1));
                timer_.async_wait(boost::bind(&TimerImpl::TimerTick, this, boost::asio::placeholders::error));
                listener_->TimerTicked(time_remaining_);
            } else {
                listener_->TimerEnded();
            }
        }
    }
}

ViewController.h

#import <UIKit/UIKit.h>
#import "CPPTTimerListener.h"
@interface ViewController : UIViewController<CPPTTimerListener>
@property (nonatomic, strong) IBOutlet UILabel *timerLabel;
@end

ViewController.m

#import "ViewController.h"
#import "CPPTTimer.h"
@interface ViewController () {
    CPPTTimer *_timer;
}
@end
@implementation ViewController
@synthesize timerLabel;
- (void)viewDidLoad {
    [super viewDidLoad];
    // initialize the timer
    _timer = [CPPTTimer createWithListener:self];
    // start a 5 second timer
    [_timer startTimer:5];
}
# pragma mark CPPTTimerListener methods
- (void)timerEnded {
    NSLog(@"Obj-C: timerEnded.");
}
- (void)timerTicked:(int32_t)secondsRemaining {
    NSLog(@"Obj-C: timerTicked with %d seconds remaining.", secondsRemaining);
    // without dispatch_async, background thread warning is thrown
    dispatch_async(dispatch_get_main_queue(), ^{
        timerLabel.text = [NSString stringWithFormat:@"%d", secondsRemaining];
    });
}
@end