这时看看系统设置中的other link flags是否有使用-weak_library /usr/lib/libSystem.B.dylib

如果有使用-weak-lSystem来代替

?

这种错误出现在模拟器，真机上不会。

The problem is simply a bug in the iOS Simulator. The codes works fine on the device.

I've filled a radar on Apple's bug reporter (radar://9470793)

EDIT: Just found out : -weak_library /usr/lib/libSystem.B.dylib breaks the iOS Simulator. Use -weak-lSystem instead.