> Another solution would be to rewrite the test to not use mmap() at all:
> 
>     @precisionbigmemtest(size=_4G + 4, memuse=1)
>     def test_big_buffer(self, size):
>         if size < _4G + 4:
>             self.skipTest("not enough free memory, need at least 4 GB")
>         data = bytearray(_4G + 4)
>         data[-4:] = b"asdf"
>         self.assertEqual(zlib.crc32(data), 3058686908)
>         self.assertEqual(zlib.adler32(data), 82837919)
> 
> This is more consistent with the other bigmem tests in test_zlib, but
> I'm guessing it will mean that the test gets run much less often (since a
> lot of machines won't have enough memory). If that's OK, then I'd prefer
> doing it this way (since it keeps things simpler).

I think there's basically noone and nothing (even among the buildbots)
that runs bigmem tests on a regular basis, so I'd much rather keep the
mmap() solution, even if that means it must be skipped on OS X.