Re: [dpdk-dev] [PATCH] eal: fix build of external apps with clang on armv8

["Richardson, Bruce" <bruce.richardson@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Ilya Maximets
> Sent: Monday, January 14, 2019 4:15 PM
> To: dev@dpdk.org; Thomas Monjalon <thomas@monjalon.net>
> Cc: Pavan Nikhilesh <pbhagavatula@marvell.com>; Ilya Maximets
> <i.maximets@samsung.com>; stable@dpdk.org
> Subject: [dpdk-dev] [PATCH] eal: fix build of external apps with clang on
> armv8
> 
> In case DPDK built using GCC, RTE_TOOLCHAIN_CLANG is not defined.
> But 'rte_atomic.h' is a generic header that included to the external apps
> like OVS while building with DPDK. As a result, clang build of OVS fails
> on ARMv8 if DPDK built using gcc:
> 
>     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
> 
> We need to check for current compiler, not the compiler used for DPDK
> build.
> 
> Fixes: 7bdccb93078e ("eal: fix ARM build with clang")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
> ---
>  lib/librte_eal/common/include/generic/rte_atomic.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_eal/common/include/generic/rte_atomic.h
> b/lib/librte_eal/common/include/generic/rte_atomic.h
> index b99ba4688..d0c464fb1 100644
> --- a/lib/librte_eal/common/include/generic/rte_atomic.h
> +++ b/lib/librte_eal/common/include/generic/rte_atomic.h
> @@ -212,7 +212,7 @@ rte_atomic16_exchange(volatile uint16_t *dst, uint16_t
> val);  static inline uint16_t  rte_atomic16_exchange(volatile uint16_t
> *dst, uint16_t val)  { -#if defined(RTE_ARCH_ARM64) &&
> defined(RTE_TOOLCHAIN_CLANG)
> +#if defined(RTE_ARCH_ARM64) && defined(__clang__)
>  	return __atomic_exchange_n(dst, val, __ATOMIC_SEQ_CST);  #else
>  	return __atomic_exchange_2(dst, val, __ATOMIC_SEQ_CST); @@ -495,7
> +495,7 @@ rte_atomic32_exchange(volatile uint32_t *dst, uint32_t val);
> static inline uint32_t  rte_atomic32_exchange(volatile uint32_t *dst,
> uint32_t val)  { -#if defined(RTE_ARCH_ARM64) &&
> defined(RTE_TOOLCHAIN_CLANG)
> +#if defined(RTE_ARCH_ARM64) && defined(__clang__)
>  	return __atomic_exchange_n(dst, val, __ATOMIC_SEQ_CST);  #else
>  	return __atomic_exchange_4(dst, val, __ATOMIC_SEQ_CST); @@ -777,7
> +777,7 @@ rte_atomic64_exchange(volatile uint64_t *dst, uint64_t val);
> static inline uint64_t  rte_atomic64_exchange(volatile uint64_t *dst,
> uint64_t val)  { -#if defined(RTE_ARCH_ARM64) &&
> defined(RTE_TOOLCHAIN_CLANG)
> +#if defined(RTE_ARCH_ARM64) && defined(__clang__)
>  	return __atomic_exchange_n(dst, val, __ATOMIC_SEQ_CST);  #else
>  	return __atomic_exchange_8(dst, val, __ATOMIC_SEQ_CST);
> --
> 2.17.1

Is this really architecture-specific? Would the same issue not occur on e.g. x86 or PPC?