How to understand this crash report for iPhone App - ios

Question

This iPhone App will dial and hangup a call automatically. It works on jailbroken devices.
Sometimes it will crash when hanging up a phone call.
What is the problem and how do I fix it?
Exception Type: EXC_GUARD
Exception Subtype: GUARD_TYPE_FD
Exception Message: CLOSE on file descriptor 16 (guarded with 0x08fd4dbfade2dead)
Triggered by Thread: 0
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x38cdf130 __close_nocancel + 12
1 libsystem_c.dylib 0x38c4fcd5 fclose + 69
2 libCGFreetype.A.dylib 0x2e56dde5 FT::file_stream::~file_stream() + 25
3 libCGFreetype.A.dylib 0x2e56ddbb FT::file_stream::~file_stream() + 7
4 libCGFreetype.A.dylib 0x2e5730b5 destroy_face + 117
5 libCGFreetype.A.dylib 0x2e573039 FT_Done_Face + 93
6 libCGFreetype.A.dylib 0x2e5658e3 FT::face_release(FT_FaceRec_*) + 95
7 libCGFreetype.A.dylib 0x2e568f31 FT::font::~font() + 269
8 libCGFreetype.A.dylib 0x2e568e13 FT::font::~font() + 7
9 libCGFreetype.A.dylib 0x2e56fa77 (anonymous namespace)::release_private_data(void*) + 55
10 CoreGraphics 0x2e51301f font_finalize + 27
11 CoreFoundation 0x2e2ffe2d CFRelease + 465
12 libcache.dylib 0x38bc321f _value_entry_remove + 139
13 libcache.dylib 0x38bc25b3 _entry_remove + 195
14 libcache.dylib 0x38bc2761 cache_remove_with_block + 129
15 CoreFoundation 0x2e307fcb __CFNotificationCenterAddObserver_block_invoke + 123
16 CoreFoundation 0x2e391e6f __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 11
17 CoreFoundation 0x2e305aad _CFXNotificationPost + 1717
18 Foundation 0x2ecebec1 -[NSNotificationCenter postNotificationName:object:userInfo:] + 69
19 UIKit 0x30bd7e79 -[UIApplication _handleApplicationSuspend:eventInfo:] + 909
20 UIKit 0x30b590c3 -[UIApplication handleEvent:withNewEvent:] + 771
21 UIKit 0x30b58cf9 -[UIApplication sendEvent:] + 69
22 UIKit 0x30bbe31d _UIApplicationHandleEvent + 661
23 GraphicsServices 0x3303876b _PurpleEventCallback + 607
24 GraphicsServices 0x33038353 PurpleEventCallback + 31
25 CoreFoundation 0x2e39a775 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 33
26 CoreFoundation 0x2e39a70f __CFRunLoopDoSource1 + 343
27 CoreFoundation 0x2e398edb __CFRunLoopRun + 1403
28 CoreFoundation 0x2e30346d CFRunLoopRunSpecific + 521
29 CoreFoundation 0x2e30324f CFRunLoopRunInMode + 103
30 GraphicsServices 0x330372e7 GSEventRunModal + 135
31 UIKit 0x30bb8841 UIApplicationMain + 1133
32 MyApp 0x000f6d0d main (main.m:15)
33 libdyld.dylib 0x38c29ab5 start + 1

Answer 1

It looks like you have a bogus file descriptor that its trying to close. The address ends in "fade2dead", which is likely a special value to indicate freed memory. Since I don't see any of your code in the stack trace, it's likely that something is overwriting memory used by the FreeType library. I'd look for other memory stompers in your code using GuardMalloc or other similar memory tools to track down what it could be, as it's not obvious from the above stack trace.