Re: [PATCH] eal/arm: replace RTE_BUILD_BUG on non-constant

[Daniel Gregory <daniel.gregory@bytedance.com>]

On Thu, May 02, 2024 at 09:20:45AM -0700, Stephen Hemminger wrote:
> Why not:
> diff --git a/lib/eal/arm/include/rte_pause_64.h b/lib/eal/arm/include/rte_pause_64.h
> index 5cb8b59056..81987de771 100644
> --- a/lib/eal/arm/include/rte_pause_64.h
> +++ b/lib/eal/arm/include/rte_pause_64.h
> @@ -172,6 +172,8 @@ rte_wait_until_equal_32(volatile uint32_t *addr, uint32_t expected,
>  {
>         uint32_t value;
>  
> +       static_assert(__builtin_constant_p(memorder), "memory order is not a constant");
> +
>         RTE_BUILD_BUG_ON(memorder != rte_memory_order_acquire &&
>                 memorder != rte_memory_order_relaxed);
>  
> @@ -191,6 +193,8 @@ rte_wait_until_equal_64(volatile uint64_t *addr, uint64_t expected,
>  {
>         uint64_t value;
>  
> +       static_assert(__builtin_constant_p(memorder), "memory order is not a constant");
> +
>         RTE_BUILD_BUG_ON(memorder != rte_memory_order_acquire &&
>                 memorder != rte_memory_order_relaxed);
>  

What toolchain are you using? With your change I still get errors about
the expression not being constant:

In file included from ../lib/eal/arm/include/rte_pause.h:13,
                 from ../lib/eal/include/generic/rte_spinlock.h:25,
                 from ../lib/eal/arm/include/rte_spinlock.h:17,
                 from ../lib/telemetry/telemetry.c:20:
../lib/eal/arm/include/rte_pause_64.h: In function ‘rte_wait_until_equal_16’:
../lib/eal/arm/include/rte_pause_64.h:156:23: error: expression in static assertion is not constant
156 |           static_assert(__builtin_constant_p(memorder), "memory order is not a constant");
    |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I'm cross-compiling with GCC v12.2 using the
config/arm/arm64_armv8_linux_gcc cross-file, and enabling
RTE_ARM_USE_WFE by uncommenting it in config/arm/meson.build and setting
its value to true.