Is using #pragma warning push/pop the right way to temporarily alter warning level?
Once in a while it's difficult to write C++ code that wouldn't emit warnings at all. Having warnings enabled is however a good idea. So it is often necessary to disable warnings around some specific construct and have them enables in all other pieces of code.
I've seen two ways of doing that so far.
The first one is to use #pragma warning( push ) and #pragma warning( pop ):
#pragma warning( push )
#pragma warning( disable: ThatWarning )
//code with ThatWarning here
#pragma warning( pop )
The second is to use #pragma warning( default ):
#pragma warning( disable: ThatWarning )
//code with ThatWarning here
#pragma warning( default: ThatWarning )
The problem I see in the second variant is that it discards the original warning level - the warning might have been off before that or its warning level might have been altered. Using default would discard those alterations.
The first approach looks clean. Are there any problems with it? Are there any better ways to achieve the same?
Answer
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.