bigbang's Issues
getMsgForwardIMP 方法的问题
1 2 4 8的判断方式有问题吧。。
勾住CMessageWrap 崩溃
勾住CMessageWrap 程序崩溃 WeChat
can't hook NSManangedObject or it't subclass
will crash if hook NSManangedObject or it't subclass.
Hook UIView class 各种崩溃
double release导致崩溃 和 内存泄露
double release:
从 -forwardInvocation: 里的 NSInvocation 对象取参数值时,若参数值是id类型,我们会这样取:
id arg;
[invocation getArgument:&arg atIndex:i];
但这样的写法会导致 crash,这是因为 id arg 在ARC下相当于 __strong id arg,若这时在代码显式为 arg 赋值,根据 ARC 的机制,会自动插入一条 retain 语句,然后在退出作用域时插入 release 语句:
- (void)method {
id arg = [SomeClass getSomething];
// [arg retain]
...
// [arg release] 退出作用域前release
}
但我们这里不是显式对 arg 进行赋值,而是传入 -getArgument:atIndex: 方法,在这里面赋值后 ARC 没有自动给这个变量插入 retain 语句,但退出作用域时还是自动插入了 release 语句,导致这个变量多释放了一次,导致 crash。解决方法是把 arg 变量设成 __unsafe_unretained 或 __weak,让 ARC 不在它退出作用域时插入 release 语句即可:
__unsafe_unretained id arg;
[invocation getReturnValue:&arg];
还可以通过 __bridge 转换让局部变量持有返回对象,这样做也是没问题的:
id returnValue;
void *result;
[invocation getReturnValue:&result];
returnValue = (__bridge id)result;
内存泄露:
当 NSInvocation 调用的是 alloc 时,返回的对象并不会释放,造成内存泄露,只有把返回对象的内存管理权移交出来,让外部对象帮它释放才行:
id returnValue;
void *result;
[invocation getReturnValue:&result];
if ([selectorName isEqualToString:@"alloc"] || [selectorName isEqualToString:@"new"] || [selectorName isEqualToString:@"copy"] || [selectorName isEqualToString:@"mutableCopy"]) {
returnValue = (__bridge_transfer id)result;
} else {
returnValue = (__bridge id)result;
}
这是因为 ARC 对方法名有约定,当方法名开头是 alloc / new / copy / mutableCopy 时,返回的对象是 retainCount = 1 的,除此之外,方法返回的对象都是 autorelease 的,按上一节的说法,对于普通方法返回值,ARC 会在赋给 strong 变量时自动插入 retain 语句,但对于 alloc 等这些方法,不会再自动插入 retain 语句:
id obj = [SomeObject alloc];
//alloc 方法返回的对象 retainCount 已 +1,这里不需要retain
id obj2 = [SomeObj someMethod];
//方法返回的对象是 autorelease,ARC 会再这里自动插入 [obj2 retain] 语句
而 ARC 并没有处理非显式调用时的情况,这里动态调用这些方法时,ARC 都不会自动插入 retain,这种情况下,alloc / new 等这类方法返回值的 retainCount 是会比其他方法返回值多1的,所以需要特殊处理这类方法。
具体怎么用?
在didFinishLaunchingWithOptions里调用了[BigBang hookClass:@"BaseMsgContentViewController"];
但是进入微信聊天界面没有出现任何log呢?
It would be better to use class_replaceMethod
Line 86 in 2ca5bcd
If the class has overridden the -[WhateverClass forwardInvocation:]
method, then calling the class_addMethod
function will lead to fatal error. However, class_replaceMethod
will act like class_addMethod
if there isn't such -[WhateverClass forwardInvocation:]
method, or replace the method as expected if there is one.
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