前言
看此篇文章之前请先阅读xcode调试效率.
ios9.0上遇到一个问题，UITableView中长按section，如果我们的交互中要求弹出menu菜单，那么就会出现如图所示的必现崩溃
"操作"
安装lldb的malloc命令
vim ~/.lldbinit
command script import lldb.macosx.heap
按一下esc
wq 保存退出
一. 分析
问题:
1.这个NSDictionary到底是什么?是UITableView的数据源吗？
2.如果是数据源是否是多线程导致的呢？(NSDictionary在多线程下如未处理好极容易崩溃,set和get同时调用的时候,一个对象被remove之后野指针了，然后get操作会立马导致崩溃)
- 是否是
mrc导致问题？
验证过程:
1.由于工程比较大，建议先写一个demo去做。(大工程的一些配置选项可能导致lldb的某些命令无法使用），这一点耗费了我们很大的精力去分析NSZombie的malloc历史，都没有结果
结果:
在工程中拆分出demo之后，由于我们根本没有NSDictionary，所以排除了这种情况，但是为什么会有这个问题呢。这个NSDictionay又是什么呢?
二. 过程分析
1. 查看崩溃源
(lldb) command script import "lldb.macosx.heap"
(lldb) bt
* thread #1: tid = 0xbe55, 0x0000000100ded805 libobjc.A.dylib`objc_msgSend + 5, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x1)
frame #0: 0x0000000100ded805 libobjc.A.dylib`objc_msgSend + 5
frame #1: 0x00000001012fb1a5 CoreFoundation`-[NSDictionary descriptionWithLocale:indent:] + 373
frame #2: 0x000000010097d3f4 Foundation`_NSDescriptionWithLocaleFunc + 64
frame #3: 0x000000010124fe4d CoreFoundation`__CFStringAppendFormatCore + 9597
frame #4: 0x000000010133c563 CoreFoundation`_CFStringCreateWithFormatAndArgumentsAux2 + 259
frame #5: 0x000000010134ce0a CoreFoundation`_CFLogvEx2 + 154
frame #6: 0x000000010134cf6b CoreFoundation`_CFLogvEx3 + 171
frame #7: 0x0000000100a53d5e Foundation`_NSLogv + 117
frame #8: 0x00000001009a35e2 Foundation`NSLog + 152
* frame #9: 0x000000010183fc5e UIKit`-[UITableView reloadData] + 1853
frame #10: 0x00000001008d436c Test`-[SectionHeader showPendingMenu](self=0x00007fab6b443250, _cmd="showPendingMenu") + 572 at FirstViewController.m:47
frame #11: 0x00000001008d411b Test`-[SectionHeader longPress](self=0x00007fab6b443250, _cmd="longPress") + 43 at FirstViewController.m:27
frame #12: 0x0000000101bc6b40 UIKit`_UIGestureRecognizerSendTargetActions + 153
frame #13: 0x0000000101bc36af UIKit`_UIGestureRecognizerSendActions + 162
frame #14: 0x0000000101bc1f01 UIKit`-[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 822
frame #15: 0x0000000101bc93f3 UIKit`___UIGestureRecognizerUpdate_block_invoke809 + 79
frame #16: 0x0000000101bc9291 UIKit`_UIGestureRecognizerRemoveObjectsFromArrayAndApplyBlocks + 342
frame #17: 0x0000000101bbaeb4 UIKit`_UIGestureRecognizerUpdate + 2624
frame #18: 0x00000001012899d7 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
frame #19: 0x0000000101289947 CoreFoundation`__CFRunLoopDoObservers + 391
frame #20: 0x000000010127f59b CoreFoundation`__CFRunLoopRun + 1147
frame #21: 0x000000010127ee98 CoreFoundation`CFRunLoopRunSpecific + 488
frame #22: 0x0000000104a5aad2 GraphicsServices`GSEventRunModal + 161
frame #23: 0x000000010170a676 UIKit`UIApplicationMain + 171
frame #24: 0x00000001008d4c9f Test`main(argc=1, argv=0x00007fff5f32c618) + 111 at main.m:14
frame #25: 0x00000001039e992d libdyld.dylib`start + 1
frame #26: 0x00000001039e992d libdyld.dylib`start + 1
2. 异常截获
"操作"
通过条件断点我们查看最后一次调用的地方，然后打印当前寄存器的值
(lldb) register read
General Purpose Registers:
rax = 0x0000000109a1b001 CoreFoundation`_CFRuntimeGetClassWithTypeID + 17
rbx = 0x00007feb75041a70
rcx = 0x0000000000000000
rdx = 0x0000000000000000
rdi = 0x00007feb75041a70
rsi = 0x0000000109c8db63 "descriptionWithLocale:"
rbp = 0x00007fff56c08380
rsp = 0x00007fff56c08368
r8 = 0x0000000080000000
r9 = 0x000000000000001f
r10 = 0x00007feb736203e0
r11 = 0x0000000109ca0ef0 (void *)0x0000000109ca0f18: __NSCFDictionary
r12 = 0x00007feb7346f180
r13 = 0x00007fff56c08fe0
r14 = 0x0000000000000000
r15 = 0x000000010a98788e "There are visible views left after reusing them all: %@"
rip = 0x0000000109a1b010 CoreFoundation`-[NSDictionary descriptionWithLocale:]
rflags = 0x0000000000000246
cs = 0x000000000000002b
fs = 0x0000000000000000
gs = 0x0000000000000000
通过
"操作"
我们可以去找到rdi,这个返回参数。此时去找这个参数的地址
x00007fc93a638050: malloc( 64) -> 0x7fc93a638050 __NSCFDictionary.NSMutableDictionary.NSDictionary.NSObject.isa
stack[0]: addr = 0x7fc93a638050, type=malloc, frames:
[0] 0x000000010bb44391 libsystem_malloc.dylib`malloc_zone_malloc + 107
[1] 0x00000001091b3c36 CoreFoundation`_CFRuntimeCreateInstance + 310
[2] 0x00000001091b3712 CoreFoundation`CFBasicHashCreate + 114
[3] 0x00000001091b6674 CoreFoundation`CFDictionaryCreateMutable + 212
[4] 0x00000001097d482e UIKit`-[UITableView _setupTableViewCommon] + 137
[5] 0x00000001097d4e89 UIKit`-[UITableView initWithFrame:style:] + 205
[6] 0x000000010886e63e Test`-[FirstViewController loadView] + 254 at FirstViewController.m:0
[7] 0x000000010982f47c UIKit`-[UIViewController loadViewIfRequired] + 139
[8] 0x0000000109872c26 UIKit`-[UINavigationController _layoutViewController:] + 54
CFDictionaryCreateMutable是关键方法，通过它我们知道了如何去分配对象，理想当然，我们得去找到系统的CFDictionary，这时候会发现有一个CFDictionarySetValue的方法
三. 解决方案
1. hook截获
要截获CounFoundation库的C方法，普通的oc的swizzle当然是做不到的，但是幸好有facebook提供的fishhook，fishhook原理可以参照iOS安全攻防（十七）：Fishhook.
我们现在来截获一把,
"key的值"
，惊喜的事情出现了，此时的
key的值竟然是0x01，明显的错误啊！内部实现应该是将某个整形树枝给一个NSObject的指针了。
2. 替换判断
void my_CFDictionarySetValue(CFMutableDictionaryRef theDict, const void *key, const void *value) {
NSLog(@"wym Calling my_CFDictionarySetValue, %p, k:%p, v:%p\n", theDict, key, value);
const void *newKey = key;
if ((int)key == 1 && [NSStringFromClass([(__bridge NSObject *)value class]) isEqualToString:@"SectionHeader"]) {
newKey = (__bridge void *)[NSNumber numberWithUnsignedInteger:[(__bridge NSObject *)value hash]];
//NSLog(@"%@", [NSThread callStackSymbols]);
}
orig_CFDictionarySetValue(theDict, newKey, value);
}
这样我们就不会崩溃了。
3. 结论
整个事情的来龙去脉已经清楚了，这里提供了只是提供一个思路去解决问题。但是实际开发中不推荐这么去做，这个方法会对app性能有影响，建议用UIButton去模拟规避这个问题。
这个问题的解决并不是本人，只是对大神岳明哥的思路进行了总结，一切版权以及所有权归岳明哥所有！非经作者允许不得转载！～
