RFR: JDK-8285730: unify _WIN32_WINNT settings [v3]

[Erik Joelsson]

On Tue, 3 May 2022 07:10:58 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

>> Currently we set _WIN32_WINNT at various places in the codebase; this is used to target a minimum Windows version we want to support. See also for more detailled information :
>> https://docs.microsoft.com/en-us/windows/win32/winprog/using-the-windows-headers?redirectedfrom=MSDN#setting-winver-or-_win32_winnt
>> Macros for Conditional Declarations
>> "Certain functions that depend on a particular version of Windows are declared using conditional code. This enables you to use the compiler to detect whether your application uses functions that are not supported on its target version(s) of Windows."
>> 
>> However currently we have quite a lot of differing settings of _WIN32_WINNT in the codebase ; setting _WIN32_WINNT to 0x0601 (Windows 7) where possible would make sense because we have this setting already at   java_props_md.c  (so targeting older Windows versions at other places is most likely not useful).
>
> Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Adjust Copyright year in wepoll.c

If we define this centrally using compiler flags, then we should not also update each location in the source. Those need to either be removed or left alone. In the cases where the source definition is guarded with an ifndef and there is a comment explaining why a particular version of windows is required, keeping it around could make sense. But on the other hand, since those defines are overridden using flags, they are likely to bit rot over time so we might as well just remove all of them.

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PR: https://git.openjdk.java.net/jdk/pull/8428