Comment 19 for bug 564920

Well, it's not completely arbitrary. It's the size that was used previous to php 5.2.10. See _php_stream_mmap_range() in main/streams/mmap.c.

In my limited testing, it does solve the issue. Unfortunately, it also has the side effect of re-introducing php bug #48309 for files over 4MB.

Maybe making it size_t - 1 would be better?