From: Eric Wong <normalperson@...>
Date: 2012-03-07T17:35:55+09:00
Subject: Re: [C extension] How to detect Linux Kernel and glibc version?

I単aki Baz Castillo <ibc@aliax.net> wrote:
> Hi, for a Ruby C extension I need to check in extconf.rb the Linux
> kernel and glibc version in which the extension is being compiled (so
> when running "gem install xxxx"). I need to know this information in
> order to use the accept4 system call which exists from kernel 2.6.28
> and from glibc 2.10 (both conditions must be satisfied).

kgio just uses: have_func('accept4', %w(sys/socket.h))

I recently added an extra check for SOCK_* macros because of
Debian GNU/kFreeBSD:

http://bogomips.org/kgio.git/patch/?id=56cce133d979c22bbef80fdba1881d8f40876e2f

> Also, no idea to get the current "glibc" version.

No need to care about kernel version or glibc version.
I try to avoid version-based checks entirely (not always possible).

The trickier case is handling ENOSYS, because I've seen folks run into
issues where code gets built on a newer machine and deployed on an old
one.