linux-kernel - Re: [V2][PATCH] selftests/x86: Fix error: variably modified 'altstack

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Date:   Mon, 23 Aug 2021 14:29:41 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Jun Miao <jun.miao@...driver.com>, shuah@...nel.org
Cc:     linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [V2][PATCH] selftests/x86: Fix error: variably modified
 'altstack_data' at file scope

On 8/23/21 7:56 AM, Jun Miao wrote:
> Based on glibc 2.33 -> 2.34, there is one new feature:
> 
> NEWS for version 2.34
> =====================
> Major new features:
> * Add _SC_MINSIGSTKSZ and _SC_SIGSTKSZ.  When _DYNAMIC_STACK_SIZE_SOURCE
>    or _GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ are no longer
>    constant on Linux.  MINSIGSTKSZ is redefined to sysconf(_SC_MINSIGSTKSZ)
>    and SIGSTKSZ is redefined to sysconf (_SC_SIGSTKSZ).  This supports
>    dynamic sized register sets for modern architectural features like
>    Arm SVE.
> 
> Build error with the GNU C Library 2.34:
> DEBUG:	| sigreturn.c:150:13: error: variably modified 'altstack_data' at file scope
> | sigreturn.c:150:13: error: variably modified 'altstack_data' at file scope
> DEBUG:	|   150 | static char altstack_data[SIGSTKSZ];
> |   150 | static char altstack_data[SIGSTKSZ];
> DEBUG:	|       |             ^~~~~~~~~~~~~
> 

Please give more context on why this change is needed?

Doesn't look like you tried to compile this patch before
sending this to me.

> Signed-off-by: Jun Miao <jun.miao@...driver.com>


thanks,
-- Shuah