Clang Error on“Potential null dereference”。 [英] Clang Error on "Potential null dereference."

问题描述

我继续在以下类型的代码上得到Clang错误，我不知道为什么他们错误或如何解决他们Clang的满意：

I keep getting Clang errors on the following type of code and I can't figure out why they're erroneous or how to resolve them to Clang's satisfaction:

+ (NSString *)checkForLength: (NSString *)theString error: (NSError **)error {
    BOOL hasLength = ([theString length] > 0);
    if (hasLength) return theString;
    else {
        *error = [NSError errorWithDomain:@"ErrorDomain" code:hasLength userInfo:nil];
        return nil;
    }
}

省略示例的完全Clang反对，所以它是说明性的），Clang balks在错误分配行与以下反对：

Leaving aside the utterly-contrived nature of the example (which Clang did object to so it's illustrative enough), Clang balks at the error assignment line with the following objection:

潜在的空解引用。根据创建和返回 NSError Objects中的编码标准，参数error可以为null。

Potential null dereference. According to coding standards in 'Creating and Returning NSError Objects' the parameter 'error' may be null.

我喜欢有一个原始的Clang报告。我读过引证文件，我看不到一个方法来做预期;我检查了一些开源的Cocoa库，这似乎是一个常见的成语。任何想法？

I like having a pristine Clang report. I've read the cited document and I can't see a way to do what's expected; I checked some open-source Cocoa libraries and this seems to be a common idiom. Any ideas?

推荐答案

执行预期的方式如清单3-5所示。你的示例代码：

The way to do what's expected is shown in listing 3-5 in that document. With your example code:

+ (NSString *)checkForLength: (NSString *)theString error: (NSError **)error {
    BOOL hasLength = ([theString length] > 0);
    if (hasLength) return theString;
    else {
        if (error != NULL) *error = [NSError errorWithDomain:@"ErrorDomain" code:hasLength userInfo:nil];
        return nil;
    }
}

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