ax_have_epoll
=============

Synopsis
********

     AX_HAVE_EPOLL([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
     AX_HAVE_EPOLL_PWAIT([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])

Description
***********

This macro determines whether the system supports the epoll I/O event interface. A neat usage example would be:

       AX_HAVE_EPOLL(
         [AX_CONFIG_FEATURE_ENABLE(epoll)],
         [AX_CONFIG_FEATURE_DISABLE(epoll)])
       AX_CONFIG_FEATURE(
         [epoll], [This platform supports epoll(7)],
         [HAVE_EPOLL], [This platform supports epoll(7).])

The epoll interface was added to the Linux kernel in version 2.5.45, and the macro verifies that a kernel newer than this is installed. This check is somewhat unreliable if <linux/version.h> doesn't match the running kernel, but it is necessary regardless, because glibc comes with stubs for the epoll_create(), epoll_wait(), etc. that allow programs to compile and link even if the kernel is too old; the problem would then be detected only at runtime.

Linux kernel version 2.6.19 adds the epoll_pwait() call in addition to epoll_wait(). The availability of that function can be tested with the second macro. Generally speaking, it is safe to assume that AX_HAVE_EPOLL would succeed if AX_HAVE_EPOLL_PWAIT has, but not the other way round.

Source Code
***********

Download the latest version of ax_have_epoll.m4 (http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_have_epoll.m4) or browse the macro's revision history (http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=history;f=m4/ax_have_epoll.m4).

License
*******

Copyright © 2008 Peter Simons simons@cryp.to

Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. This file is offered as-is, without any warranty.