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

[Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>]

On Tue, Apr 10, 2018 at 11:35:15PM +0200, Thomas Monjalon wrote:
> 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?

I have tried with clang 4/5/6 and all have the same issue.

>
> 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
>
>
>