跨平台宏,用于沉默未使用的变量警告 [英] cross platform macro for silencing unused variables warning
问题描述
在从Visual Studio(2008)移植一大段C ++代码到Xcode(4.4+),我遇到了如下行:
UNUSED_ALWAYS(someVar);
UNUSED_ALWAYS(x)
code> UNUSED(x))宏扩展为 x
这似乎使Visual C ++沉默。
对于Clang,我通常使用 #pragma未使用的x
指令。 p>
UNUSED_ALWAYS
和 UNUSED
宏定义在人为 windows.h
头,我控制它包含一些实用程序来帮助Xcode编译Windows的东西。
方法定义 UNUSED(x)
展开为 #pragma未使用x
?我试过这个,Clang无法接受:
#define UNUSED(x)#pragma unused(x)
我也尝试过:
#define UNUSED(x)(void)(x)
Yup - 您可以对GCC和Clang使用此方法:
#define MON_Internal_UnusedStringify(macro_arg_string_literal)#macro_arg_string_literal
#define MONUnusedParameter(macro_arg_parameter)_Pragma(MON_Internal_UnusedStringify $ b
虽然我们已经定义了(void)
对于clang,看起来Clang现在支持stringify和 _Pragma
方法。 _Pragma
为C99。
In porting a large piece of C++ code from Visual Studio (2008) to Xcode (4.4+), I encounter lines such as:
UNUSED_ALWAYS(someVar);
the UNUSED_ALWAYS(x)
(through UNUSED(x)
) macro expands to x
which seems to silence Visual C++ just fine. It's not enough for Clang however.
With Clang, I usually use the #pragma unused x
directive.
The UNUSED_ALWAYS
and UNUSED
macros are defined in an artificial windows.h
header which I control that contains a number of utilities to help Xcode compile Windows stuff.
Is there a way to define UNUSED(x)
to expand to #pragma unused x
? I tried this, which Clang fails to accept:
#define UNUSED(x) #pragma unused(x)
I also tried:
#define UNUSED(x) (void)(x)
Which seems to work. Did I miss anything?
Yup - you can use this approach for GCC and Clang:
#define MON_Internal_UnusedStringify(macro_arg_string_literal) #macro_arg_string_literal
#define MONUnusedParameter(macro_arg_parameter) _Pragma(MON_Internal_UnusedStringify(unused(macro_arg_parameter)))
although mine did have the (void)
approach defined for clang, it appears that Clang now supports the stringify and _Pragma
approach above. _Pragma
is C99.
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