split of issue3871.

Would it be better to define all the things in "winreparse.h" with names that are less likely to conflict, say Py_REPARSE_DATA_BUFFER etc? This would be a more general way to avoid conflicts, and also avoid hacking the configure script.

Also, is the “#ifndef MAXIMUM_REPARSE_DATA_BUFFER_SIZE” condition necessary?

Here is a patch implementing my suggestion to unconditionally define everything, prefixed with Py_ instead. Not tested on a normal Windows build.

Worth checking if the headers in VC14 have the structure now, as it may simplify the whole thing.

If not, I'd add a leading underscore to the name so nobody confuses it for public API in the future.

Leading underscore is a good idea.

I have no idea if VC14 includes the structure, but I suspect if it was added with this name, we would know because it would cause the same conflict that Min GW caused.

REPARSE_DATA_BUFFER is defined in the WDK filesystem header, km\ntifs.h. It's not defined in the user-mode SDK.

I think the WDK is still separate from the Windows SDK, so probably best to keep the custom definition with a comment specifying which file it came from (so whoever diagnoses an obscure issue in the future can find it quickly).

With the comment, I'm fine with the patch. If you haven't built on MSVC then keep an eye on the build bots until it goes through in case something unpredictable happens.

New changeset e4ddfa61199c by Martin Panter in branch 'default':
Issue #17599: Use unique _Py_REPARSE_DATA_BUFFER etc names to avoid conflict
https://hg.python.org/cpython/rev/e4ddfa61199c

Thanks for your feedback. I add a reference to km\ntifs.h in the comment. The buildbots seem generally happy with the change. (One timed out in the tests, but that seems to be an existing intermittent problem.)