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New way for syncing with kernel headers
- From: Florian Weimer <fweimer at redhat dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Fri, 8 Dec 2017 14:21:27 +0100
- Subject: New way for syncing with kernel headers
- Authentication-results: sourceware.org; auth=none
Would this be an acceptable way to obtain definitions from the Linux
headers in places where namespace cleanliness is not a must?
/* Obtain the definitions of the MEMBARRIER_CMD_* constants. */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 14, 0)
# include <linux/membarrier.h>
/* Definitions from Linux 4.14 follow. */
MEMBARRIER_CMD_QUERY = 0,
MEMBARRIER_CMD_SHARED = 1,
MEMBARRIER_CMD_PRIVATE_EXPEDITED = 8,
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = 16,
The idea is to have a built-in fallback definition in case the installed
kernel headers are too old. But for newer kernels, the UAPI header is
used, to avoid duplicate definitions and a need for maintaining our own
The inline copy of the definitions reflects what is needed for building
glibc itself (including tests) and the manual. But if the end user
installs newer kernel headers, their definitions are immediately
available for use with glibc-based applications. Eventually, we can
remove the inline copy once the minimum kernel version for building
moves past the baseline requirement.
Header include ordering does not matter because <linux/membarrier.h> has
its own include guard.
Has this already been tried? Do you see any downsides?