使用 # 杂注警告推/弹出是临时更改警告级别的正确方法吗？

偶尔很难编写完全不会发出警告的 C + + 代码。然而，启用警告是一个好主意。因此，通常有必要禁用某些特定构造周围的警告，并在所有其他代码段中启用这些警告。

到目前为止，我已经看到了两种方法。

第一种是使用 #pragma warning( push )和 #pragma warning( pop ):

 #pragma warning( push )
#pragma warning( disable: ThatWarning )
//code with ThatWarning here
#pragma warning( pop )

第二种是使用 #pragma warning( default ):

 #pragma warning( disable: ThatWarning )
//code with ThatWarning here
#pragma warning( default: ThatWarning )

我在第二个变体中看到的问题是，它丢弃了原来的警告级别——在此之前警告可能已经关闭，或者警告级别可能已经更改。使用 default将放弃这些更改。

第一种方法看起来很干净。它有什么问题吗? 有没有更好的方法来达到同样的效果？

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最佳答案

The first method is the best way to do it, IMO. I know of no problems with it.

Simply bear in mind that a #pragma is compiler specific so don't expect it to work on every compiler out there :)

小开

I have no problems with the first variant. May be the better way is to use the following:

 #pragma warning( push )
#pragma warning( once: ThatWarning )
//code with ThatWarning here
#pragma warning( pop )

This will let you know that there're still warnings in the code, but the warning messages will not be so annoying. But that is the matter of taste.

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The correct approach (although a bit ugly)

#ifdef _MSC_VER
#pragma warning( push )
#pragma warning( once: ThatWarning )
#endif
//code with ThatWarning here
#ifdef _MSC_VER
#pragma warning( pop )
#endif
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You can disable specific warnings in the project or file options and this setting applies as the 'default' per those #pragmas at the relevant scope. Some of the warnings in VS2005 are so useless/annoying that this cleans up the output quite a bit, if using /W4.

This is in Properties under Configuration Properties -> C/C++ -> Advanced.

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Too late for sharptooth but for all the googlers out there:

#pragma warning ( suppress: ThatWarning )
// one single line with ThatWarning

is short for (generally since VS 2008, but in VS 2005 for Code Analyzer warnings only):

#pragma warning ( push )
#pragma warning ( disable: ThatWarning )
// one single line with ThatWarning
#pragma warning ( pop )
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This will work with multiple compilers (and different versions of compilers).

Header "push"

#if defined(__clang__)
# pragma clang diagnostic push
#endif


#if defined(_MSC_VER)
# pragma warning(push)
#endif


#if defined(YOUR_FAVORITE_COMPILER)
# pragma your compiler push warning
#endif

Header "pop"

#if defined(__clang__)
# pragma clang diagnostic pop
#endif


#if defined(_MSC_VER)
# pragma warning(pop)
#endif

Some warning

#if defined(__clang__)
# pragma clang diagnostic ignored "-Wunused-parameter"
# pragma clang diagnostic ignored "-Wunused-variable"
#  if __has_warning("-Wnew-special-warning")
#   pragma clang diagnostic ignored "-Wnew-special-warning"
#  endif
#endif


#if defined(_MSC_VER)
# pragma warning(disable: 4100) // unreferenced formal parameter
# if _MSC_VER > _MSC_SOME_VERSION
#  pragma warning(disable: xxxx) // disable one more for special version
# endif
#endif

Usage

// This code reports warnings
// ...
#include <ignore_compiler_warning/push>
#include <ignore_compiler_warning/warning_type_1>
#include <ignore_compiler_warning/warning_type_2>
#include <ignore_compiler_warning/warning_type_3>
// This code ignores warnings type_{1,2,3}
// ...
#include <ignore_compiler_warning/pop>
// Back to reporting warnings
// ...

Additionally include guards can check that there is no double push/pop/disable-warning pragmas.

Update

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The first approach allows you change the specific warning setting in a local scope. It first stores all the current warning state by push into stack, apply your warning modifications, then restore (pop) to last warning state.

#pragma warning( push ) #pragma warning( once: ThatWarning ) //code with ThatWarning here #pragma warning( pop )


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