XCode 4.2.1 + Enable Guard Malloc -> immediate crash?

Question

Anybody know how to solve this? With Xcode 4.2.1, turning on Enable Guard Malloc and running on iPhone Simulator 5, the app immediately crashes, and this is the stack trace:

#0  0x00000000 in <????> ()
#1  0x91594ef3 in mig_get_reply_port ()
#2  0x9158e70c in mach_ports_lookup ()
#3  0x031f0124 in _xpc_domain_init_local ()
#4  0x031edeb1 in _libxpc_initializer ()
#5  0x8fe5d15b in __dyld__ZN16ImageLoaderMachO18doModInitFunctionsERKN11ImageLoader11LinkContextE ()
#6  0x8fe5ccc0 in __dyld__ZN16ImageLoaderMachO16doInitializationERKN11ImageLoader11LinkContextE ()
#7  0x8fe5a220 in __dyld__ZN11ImageLoader23recursiveInitializationERKNS_11LinkContextEjRNS_21InitializerTimingListE ()
#8  0x8fe5a1b6 in __dyld__ZN11ImageLoader23recursiveInitializationERKNS_11LinkContextEjRNS_21InitializerTimingListE ()
#9  0x8fe5a1b6 in __dyld__ZN11ImageLoader23recursiveInitializationERKNS_11LinkContextEjRNS_21InitializerTimingListE ()
#10 0x8fe5a1b6 in __dyld__ZN11ImageLoader23recursiveInitializationERKNS_11LinkContextEjRNS_21InitializerTimingListE ()
#11 0x8fe5a1b6 in __dyld__ZN11ImageLoader23recursiveInitializationERKNS_11LinkContextEjRNS_21InitializerTimingListE ()
#12 0x8fe5b1c0 in __dyld__ZN11ImageLoader15runInitializersERKNS_11LinkContextERNS_21InitializerTimingListE ()
#13 0x8fe4f626 in __dyld__ZN4dyld24initializeMainExecutableEv ()
#14 0x8fe53ef2 in __dyld__ZN4dyld5_mainEPK12macho_headermiPPKcS5_S5_ ()
#15 0x8fe4d2ef in __dyld__ZN13dyldbootstrap5startEPK12macho_headeriPPKclS2_ ()
#16 0x8fe4d063 in __dyld__dyld_start ()

Answer 1

You san see this answer: Application crashes on simulator 5.0 before reaching main.m

However, the linked solution didn't work for me. I had exactly the same diagnostic and absence of error message, but I found no "weak"-related issues in my project.pbxproj

However, I found that the cause of my problem was a deadlock in an +(void)initialize method. More precisely, in this method I was calling dispatch_sync(dispatch_get_main_queue(), ^{[some block code]}). Changing this to a dispatch_async (note the "a") solved my problem.

The way I discovered the issue was accidental. While nothing seemed to happen, the "thread" navigator of Xcode was telling me that the app itself wasn't crashed. And I accidentaly clicked on "pause" in the debugger. And suddenly it stopped exactly where the deadlock was.

Enjoy.