Re: [dpdk-dev] [PATCH] eal: fix clang compilation error on ARM64

[Thomas Monjalon <thomas@monjalon.net>]

Hi, big issue here.
This patch does not compile on Linux with ICC or GCC < 4.9
because of a missing C11 header:
	#include <stdatomic.h>

GCC 4.9 is recommended in doc/guides/linux_gsg/sys_reqs.rst.
But GCC 4.8 is used by SLES 12, RHEL 7, etc...

Note: Intel compilation tests are running with a backlog of one week,
so cannot catch such fail.

Exceptionnaly, I have decided to remove this patch pushed few hours ago
(not reverting), in order to avoid a serious "git bisect" breakage
in the middle of the git history.

We'll need to find a better way of fixing the compilation error
seen on ARM with clang.
To make it clear: I believe it is more important to preserve GCC 4.8
than clang compilation.
By the way, what is the version of clang which was causing the error?

The error was:
	include/generic/rte_atomic.h:215:9: error:
		implicit declaration of function '__atomic_exchange_2'
		is invalid in C99
	include/generic/rte_atomic.h:494:9: error:
		implicit declaration of function '__atomic_exchange_4'
		is invalid in C99
	include/generic/rte_atomic.h:772:9: error:
		implicit declaration of function '__atomic_exchange_8'
		is invalid in C99

The proposed solution was:
	Use __atomic_exchange_n instead of __atomic_exchange_(2/4/8),
	and include stdatomic.h.



10/04/2018 17:07, Thomas Monjalon:
> 06/04/2018 20:25, Pavan Nikhilesh:
> > On Fri, Apr 06, 2018 at 06:24:34PM +0200, Thomas Monjalon wrote:
> > > 06/04/2018 13:01, Pavan Nikhilesh:
> > > > Use __atomic_exchange_n instead of __atomic_exchange_(2/4/8).
> > > >
> > > > Fixes: ff2863570fcc ("eal: introduce atomic exchange operation")
[...]
> Applied (with error log), thanks