blocks|key|3258131|text|我怀疑它只是注意到一个前缀为copy的方法，并将其标记为应该返回调用者拥有的东西，因为它认为它遵循Cocoa命名约定。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3258132|当然，在您的例子中，您指的是文件之类的东西，所以这是一个可以忽略的警告。如果您将方法的名称改为类似于saveData:的名称，我敢打赌警告将消失。|3258133|entityMap^0|E|4|0|1E|9|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

I suspect it's just noticing a method with the prefix <code>copy</code> and flagging that as something that should return something that the caller owns, because it thinks it's following Cocoa naming conventions.

In your case, of course, you are referring to files and whatnot, so it's an ignorable warning. If you change the name of your method, to something like <code>saveData:</code> instead, I bet the warning will go away.

blocks|key|3258135|text|根据Memory+Management+Guide，由于该方法具有名称copy，因此分析器期望返回的对象具有%2B1保留计数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3258136|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.apple.com/mac/library/documentation/cocoa/conceptual/MemoryMgmt/Articles/mmObjectOwnership.html#//apple_ref/doc/uid/20000043-SW1^0|Z|4|2|N|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

Since the method has the name <code>copy</code> in it, the analyzer is expecting the returned object to have a +1 retain count, according to the <a href="http://developer.apple.com/mac/library/documentation/cocoa/conceptual/MemoryMgmt/Articles/mmObjectOwnership.html#//apple_ref/doc/uid/20000043-SW1" rel="nofollow noreferrer">Memory Management Guide</a>.

blocks|key|310715|text|不，这是不正确的；除非该方法包含"alloc“、"copy”、"new“或其他关键字之一，否则该方法将返回一个自动释放或托管对象，因此stringByAppendingPathComponent将返回一个自动释放的字符串。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|310716|最重要的是，您的方法"copyData“包含单词"copy"，这意味着结果应该由调用者拥有(并发布)。但是，您返回的结果已自动发布，因此它会向您显示错误消息。如果你想修复这个错误，不要自动释放。这就是：|310717|+return+[path+retain]|code-block|syntax|javascript|310718|当然，这意味着你的函数的调用者需要释放它。或者，您可以更改函数的名称，使其符合内存管理指南。|310719|不管怎样，"copyData“这个名字是不直观的。我建议您将函数重命名为"pathToSavedDataWithData“或类似的名称。能说明它实际在做什么的东西。|310720|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

No, that is incorrect; unless the method contains "alloc", "copy", "new", or one of the other keywords that implies the object will be owned by the invoker, the method returns an autoreleased or otherwise managed object, so stringByAppendingPathComponent is returning an autoreleased string.

On top of that, your method "copyData", contains the word "copy", implying that the result should be owned (and released) by the caller. However, the result you returned has been autoreleased, hence the error message that it is giving you. If you want to fix the error, don't autorelease. That is:

<pre><code> return [path retain]
</code></pre>

Of course that implies that the callers of your function need to release it. Alternatively, you can change the name of your function so that it complies with the memory management guidelines.

The name "copyData", IMHO, is unintuitive anyway. I would suggest you rename your function to "pathToSavedDataWithData" or the like. Something that says what it actually is doing.

blocks|key|3258167|text|此外，当你真的想用'+copy‘或其他东西来命名一个方法的时候，因为不管Cocoa内存管理指南，copy是方法的最佳名称，你可以用NS_RETURNS_NOT_RETAINED注释方法声明，然后Clang不会给你一个警告。所以：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3258168|//+Copies+data+from+data+to+string;+does+not+follow+the+copy+rule
-+(NSString*)copyData:(NSData*)data+NS_RETURNS_NOT_RETAINED;|code-block|syntax|javascript|3258169|entityMap^0|1T|N|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Also, for times where you really do want to name a method with 'copy' or something because regardless of Cocoa memory management guidelines, copy is the best name for the method, you can annotate the method declairation with <code>NS_RETURNS_NOT_RETAINED</code> and then Clang won't give you a warning. So:

<pre><code>// Copies data from data to string; does not follow the copy rule
- (NSString*)copyData:(NSData*)data NS_RETURNS_NOT_RETAINED;
</code></pre>

blocks|key|3044536|text|我将尝试一下这一点，并猜测无论例程的名称是否以"copy+...“开头，您都会收到完全相同的错误消息。或者不是。我只是在一个类似的场景中结束了，"copy“不是我调用的例程名称的一部分。Clang给出这个错误消息仅仅是因为我返回了一个自动释放的对象，这是一个危险的情况。做这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3044537|++return+[path+retain]++|code-block|syntax|javascript|3044538|3044539|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|K|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|L|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|M|8|@]|9|@]|A|$]]]|I|$]]

I'm going to take a stab at this and guess that you'd get the same exact error message, whether or not the name of your routine started with "copy ..." or not. I just ended up in a similar scenario and "copy" was not part of the name of the routine I was calling. Clang was giving the error message simply because I was returning an autoreleased object, a dangerous situation. Doing the 

<pre><code> return [path retain] 
</code></pre>

trick at the end as recommended by Michael took care of the problem.

I have a piece of Objective-C code that looks like the following:

<pre><code>- (NSString *)copyData:(NSData *)data
{
 NSString *path = [[[self outputDirectory] stringByAppendingPathComponent:@"archive"] stringByAppendingPathExtension:@"zip"];
 NSLog(@"Copying data to %@", path);
 [data writeToFile:path atomically:NO];
 return path;
}
</code></pre>

The code is called from an initializer that looks like this:

<pre><code>- (id)initWithData:(NSData *)data
{
 if ((self = [super init]) != nil) {
 NSString *path = [self copyData:data]; // Line 41 (referenced in warning, shown below)
 return [self initWithContentsOfFile:path];
 }
 return self;
}
</code></pre>

When running the clang static analyzer, I get the following warnings for the <code>path</code> variable:

<blockquote>
 Potential leak of an object allocated on line 41 and stored into 'path'
 
 Object with +0 retain counts returned to caller where +1 (owning) retain count is expected
</blockquote>

I'm confused. My understanding is that <code>stringByAppendingPathComponent</code> should return an autoreleased string, so it should have a net retain count of 0. (Obviously I don't want to retain it.)

I've tried altering <code>copyData:</code> to return the following, but it didn't get rid of the warning:

<pre><code>return [[path retain] autorelease];
</code></pre>

So what's the deal with this warning?

How can I fix this clang warning: "Object with +0 retain counts returned to caller where +1 (owning) retain count is expected"?

内存管理

Objective-C

我有一段Objective-C代码，如下所示：- (NSString *)copyData:(NSData *)data{    NSString *path = [[[self outputDirectory] stringByAppendingPathComponent:@"archive"] stringByAp...

问如何修复这个clang警告："Object with +0 retain returned to caller where expected +1 (owning) retain“？
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