在Objective-C中使用GCC __unused属性 [英] Using the GCC __unused attribute with Objective-C

问题描述

是否可以在Objective-C对象方法参数上使用__unused属性宏？我试着将它放置在参数声明的各个位置，但它会导致编译错误或似乎被忽略（即编译器在编译-Wall -Wextra时仍会生成未使用的参数警告）。

任何人都可以使用它吗？它只是不支持Objective-C吗？作为参考，我目前正在使用Apple的GCC 4.0.1版本。

解决方案

好的，我找到了答案...它似乎是执行Apple的gcc 4.0的一个错误。使用gcc 4.2，它按预期工作，正确的位置如下：

   - （void）someMethod：（id）__unused someParam ; 
  

如果任何人感兴趣，它在Objective-C发行说明中有记录： http://developer.apple.com/releasenotes/ Cocoa / RN-ObjectiveC / index.html＃// apple_ref / doc / uid / TP40004309-DontLinkElementID_6

请注意， ，但正如我在我的问题中所述，它实际上不会做任何事情或压制编译器发出的未使用警告。

编辑：我向苹果提交了一个bug报告这 rdar：// 6366051 。

Is it possible to use the __unused attribute macro on Objective-C object method parameters? I've tried placing it in various positions around the parameter declaration but it either causes a compilation error or seems to be ignored (i.e., the compiler still generates unused parameter warnings when compiling with -Wall -Wextra).

Has anyone been able to do use this? Is it just unsupported with Objective-C? For reference, I'm currently using Apple's build of GCC 4.0.1.

解决方案

Okay, I found the answer... it appears to be a bug with the implementation of Apple's gcc 4.0. Using gcc 4.2 it works as expected and the proper placement is the following:

-(void)someMethod:(id) __unused someParam;

It's documented in the Objective-C release notes if anyone is interested: http://developer.apple.com/releasenotes/Cocoa/RN-ObjectiveC/index.html#//apple_ref/doc/uid/TP40004309-DontLinkElementID_6

As a note, your answer will compile, Louis, but as I stated in my question it won't actually do anything or suppress the unused warning issued by the compiler.

EDIT: I filed a bug report with apple for this rdar://6366051.

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