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

[Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>]

On Wed, Apr 11, 2018 at 10:46:47AM +0200, Thomas Monjalon wrote:
> 11/04/2018 10:38, Pavan Nikhilesh:
> > 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.
>
> Do you know why the issue is not seen on x86?

Nope but I tried including the header as well as using -std=c11 in cflags but
still observing the same issue with clang.

>
>
> > > 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
>
>
>