I'm trying to figure out why do I get APR_HAS_LARGE_FILES set to zero on my linux box. I can't find any rules that makes that decision. From reading archives, I understood, that it's simply unconditionally turned off. The most recent thread on this topic seems to be: http://marc.theaimsgroup.com/?t=104646080100001&r=1&w=2
Older versions of glibc do not support compilation with large files turned on and use of sendfile(). If you want to work in those environments, you have to turn off sendfile(), which most people don't want to do in a network-intensive application (like httpd). For file-intensive apps (like perl), they don't need sendfile and would rather support large files instead.
I think the Linux kernel has optionally supported sendfile64 since 2.2, but the glibc layer doesn't expose it properly. So, you could also bypass glibc and perform the syscall directly on Linux versions with sendfile64, but only a 32-bit sendfile().
Recent versions of glibc supposedly fix it (still only shipped in bleeding-edge distro releases, I think). I think Sascha (?) posted a proof of concept that would detect newer glibc's or do the syscall itself, but it wasn't a concrete patch, IIRC. Still, you'd have to disable sendfile() with large files when you see an older glibc and no sendfile64 (which I think is a bad idea to do by default).
If you'd like to take that proof of concept and create a patch that we could apply, it'd be welcome. -- justin
