I said:
> Is anyone else seeing the same? I'm confused because I'm quite sure
> it built there recently. I suspect one of the recent changes to our
> configure stuff broke it, but I don't see the connection offhand.
The answer is that it was broken by the recent change to c.h to include
pg_config_os.h later than it had been --- much too late, in fact. If
you want to muck with _GNU_SOURCE you have to set it before any system
headers are included.
I have reverted that change. If you need some Windows-specific stuff at
the later spot in the file, please add it without risking breaking
other ports.
regards, tom lane