[dpdk-dev] [PATCH v6 2/8] eal: fix error attribute use for clang

[David Marchand]

On Wed, Jan 27, 2021 at 6:33 PM Bruce Richardson
<bruce.richardson at intel.com> wrote:
>
> Clang does not have an "error" attribute for functions, so for marking
> internal functions we need to check for the error attribute, and provide
> a fallback if it is not present. For clang, we can use "diagnose_if"
> attribute, similarly checking for its presence before use.
>
> Fixes: fba5af82adc8 ("eal: add internal ABI tag definition")
> Cc: haiyue.wang at intel.com

Cc: stable at dpdk.org

>
> Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
> ---
>  lib/librte_eal/include/rte_compat.h | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/lib/librte_eal/include/rte_compat.h b/lib/librte_eal/include/rte_compat.h
> index 4cd8f68d68..c30f072aa3 100644
> --- a/lib/librte_eal/include/rte_compat.h
> +++ b/lib/librte_eal/include/rte_compat.h
> @@ -19,12 +19,18 @@ __attribute__((section(".text.experimental")))
>
>  #endif
>
> -#ifndef ALLOW_INTERNAL_API
> +#if !defined ALLOW_INTERNAL_API && __has_attribute(error) /* For GCC */
>
>  #define __rte_internal \
>  __attribute__((error("Symbol is not public ABI"), \
>  section(".text.internal")))
>
> +#elif !defined ALLOW_INTERNAL_API && __has_attribute(diagnose_if) /* For clang */
> +
> +#define __rte_internal \
> +__attribute__((diagnose_if(1, "Symbol is not public ABI", "error"), \
> +section(".text.internal")))
> +

If the compiler has neither error or diagnose_if support, an internal
API can be called without ALLOW_INTERNAL_API.
I prefer a build error complaining on an unknown attribute rather than
silence a check.

I.e.

#ifndef ALLOW_INTERNAL_API

#if __has_attribute(diagnose_if) /* For clang */
#define __rte_internal \
__attribute__((diagnose_if(1, "Symbol is not public ABI", "error"), \
section(".text.internal")))

#else
#define __rte_internal \
__attribute__((error("Symbol is not public ABI"), \
section(".text.internal")))

#endif

#else /* ALLOW_INTERNAL_API */

#define __rte_internal \
section(".text.internal")))

#endif

-- 
David Marchand