dispatch_once调用导致崩溃 [英] dispatch_once call causes crash

问题描述

dispatch_once 在我将项目转换为ARC之后，调用导致崩溃（在模拟器中）。

dispatch_once call causes crash (in simulator) after I've converted my project to ARC.

原来的问题是，我有$ EXC_BAD_ACCESS （在objc_retain调用）崩溃在我的一个singleton对象的+（SingletonClass）shared {... dispatch_once（...， {}）; ...}方法正好在dispatch_once调用之前一行。

My original problem was that I've got EXC_BAD_ACCESS (in objc_retain call) crash in one of my singleton object's + (SingletonClass)shared { ... dispatch_once(..., ^{}); ... } method exactly one line before the dispatch_once call.

根据loggings和断点，我的代码没有运行到dispatch_once调用的块中。

Based on loggings, and breakpoints my code have not run into the dispatch_once call's block.

我不知道原因，所以我刚刚注释掉dispatch_once调用。我的应用程序没有调用没有崩溃。

I didn't know the reason, so I've just commented out the dispatch_once call. My app haven't crashed without that call.

之后，我试图把dispatch_once在我的应用程序调用的方法。基于这一点，我知道Xcode指向正好在dispatch_once调用之前的行，而不管dispatch_once调用是什么方法。

After that I've tried to put dispatch_once in a method that my app calls earlier. Based on that I know that Xcode points to the line that is exactly before the dispatch_once call regardless of the method where the dispatch_once call is.

主要的事情是一个谜对我来说，这只是可重复的，如果我在模拟器中运行的应用程序。

The main thing that is a mystery for me is that this is only reproducible if I run the app in the simulator. Running the app on a device work wihtout any problem.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    NSLog(@"I will crash if you won't delete the dispatch_once after me and you run me in the iOS Simulator... If you run me on a device there won't be any problem with me...");

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        int a = 42;
    });

    return NO;
}

推荐答案

完全相同的问题一会儿在一个基于PhoneGap的项目我转换为ARC一个回来 - 崩溃在模拟器，但不是在设备上。

I've been fighting this exact same issue for a little while on a PhoneGap-based project I'd converted to ARC a while back - crashing in the simulator but not on the device.

一个新项目和相同的代码工作确定，所以我通过项目配置看看有什么不同。

I created a fresh project and the same code worked OK, so I went through the project configuration to see what was different.

在我的情况下，我有旧的不需要的链接器标记set，具体 -weak_library /usr/lib/libSystem.B.dylib 。

In my case, I had old un-needed linker flags set, specifically -weak_library /usr/lib/libSystem.B.dylib.

构建设置的链接器标记部分修复了它。

Removing that from the "Other Linker Flags" section of "Build Settings" fixed it.

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