Clang-msvc warns of _WIN32_WINNT is reserved

[denchat]

I'm not sure if users are supposed to suppress certain warnings themselves.

[lewissbaker]

Is defining _WIN32_WINNT in a header file is somewhat of an anti-pattern?
Perhaps it should be defined only the command-line?
Maybe config.hpp should require that the build system specifies it?

[denchat]

Is it okey to use __has_include?

#if defined(_WIN32_WINNT) || defined(_WIN32)
# if !defined(_WIN32_WINNT)
#  if __has_include(<sdkddkver.h>)
#   // By default, we just use SDKDDKVer.h in the include paths
#   // for _WIN32_WINNT value
#   include <sdkddkver.h>
#   define CPPCORO_HAS_SDKDDKVER_H 1
#  else
#   define CPPCORO_HAS_SDKDDKVER_H 0
#  endif
   static_assert(CPPCORO_HAS_SDKDDKVER_H,
                 "Ensure sdkddkver.h header from WindowsSDK of your target"
                 " exists in the include paths, or otherwise explicitly"
                 " define _WIN32_WINNT as corresponding value of"
                 " your target via compile command.");
# endif
# define CPPCORO_OS_WINNT _WIN32_WINNT
#else
# define CPPCORO_OS_WINNT 0
#endif

[denchat]

Maybe config.hpp should require that the build system specifies it?

Typically _WIN32_WINNT definition depends on #include <sdkddkver.h>.

Do you intend that the build system like cake or CMAKE should be the one who defines _WIN32_WINNT without #include <sdkddkver.h> in source code?

[denchat]

CMAKE's CMAKE_SYSTEM_VERSION might not reflect the WindowsSDK version that being used.

https://stackoverflow.com/questions/9742003/platform-detection-in-cmake#comment96056421_40217291

user2019765 Feb 11 at 13:55

If CMAKE_SYSTEM_VERSION happens to be newer than the SDK version (e.g. CMAKE_SYSTEM_VERSION corresponds to Windows 10 but you only have the Windows SDK installed with Visual Studio 2010), this may lead to defining _WIN32_WINNT to a value that is not explicitly supported by the SDK. This is probably not a problem as such, but if you happen to do further checks based on the value of _WIN32_WINNT, the corresponding features might not be available during the build.

[denchat]

Well, it seems Falkon from KDE adopts this exact _WIN32_WINNT definition using CMAKE

https://phabricator.kde.org/D8079

[lewissbaker]

The intention was to let the build system specify _WIN32_WINNT to allow the application to specify the minimum version of Windows that they want to target and so restrict the set of APIs that cppcoro can use to only those that are available on that OS version or earlier, regardless of what version of the SDK the program is being built against.

If _WIN32_WINNT is not specified by the build system then we need to pick some default OS version to target. We could pick some minimum OS version for maximum compatibility or we could pick the latest version supported by the SDK or we could pick something in-between.

[denchat]

Okey then now this should be closed. Let the build system do the work.