在使用Instrumnents对程序进行内存测试的时候，发现有几处异常处理的地方提示内存泄露。经过分析得知，因为异常处理，改变代码执行路径，导致编译生成的 release 代码没有执行。
简单写了些测试代码验证：
- (void)viewDidLoad {
[super viewDidLoad];
@try {
NSMutableArray *stringList = [[NSMutableArray alloc] init];
for (int i = 0; i < 100; i++) {
[stringList addObject: @"string instance."];
}
[self throwException];
}
@catch (NSException *exception) {
NSLog(@"catch Exception : %@", exception);
}
@finally {
}
}
- (void)throwException
{
[NSException raise:@"An Exception." format:@"Exception Description."];
}
反复进出这个页面几次后，在Instruments上果然看到提示内存泄露，而且泄露的地方就指明是 @try{ } 里面创建的对象。
memory-leak
解决思路
1, 尽量不要在@try{}里面有操作，导致对象的引用引用计数增加。@try{ } 语句块里面只有有可能抛出异常的语句。
修改后的代码:
- (void)viewDidLoad {
[super viewDidLoad];
NSMutableArray *stringList = [[NSMutableArray alloc] init];
for (int i = 0; i < 100; i++) {
[stringList addObject: @"string instance."];
}
@try {
[self throwException];
}
@catch (NSException *exception) {
NSLog(@"catch Exception : %@", exception);
}
@finally {
}
}
最后用Instruments检查一下，一切正常了。
2, 查看了苹果的开发文档，发现有这么一段描述:
By default in Objective C, ARC is not exception-safe for normal releases:
It does not end the lifetime of __strong variables when their scopes are abnormally terminated by an exception.
It does not perform releases which would occur at the end of a full-expression if that full-expression throws an exception.
A program may be compiled with the option -fobjc-arc-exceptions in order to enable these, or with the option -fno-objc-arc-exceptions to explicitly disable them, with the last such argument “winning”.
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