Re: [next:akpm 129/309] net/core/sock.c:274:36: error: initializer element is not constant

[Michael Cree <mcree@orcon.net.nz>]

On 03/08/12 03:02, Fengguang Wu wrote:
> On Thu, Jul 26, 2012 at 10:06:41AM -0700, Tony Luck wrote:
>> On Tue, Jul 24, 2012 at 10:10 PM, James Bottomley
>> <James.Bottomley@hansenpartnership.com> wrote:
>>>> Here is the line in sock.i:
>>>>
>>>> struct static_key memalloc_socks = ((struct static_key) { .enabled >>>> ((atomic_t) { (0) }) });
>>>
>>> The above line contains two compound literals.  It also uses a designated
>>> initializer to initialize the field enabled.  A compound literal is not a
>>> constant expression.
>>
>> Seeing the same thing on ia64 building next-20120726.  Same fix works
>> for me ... so I'll steal this whole changelog and attributes.
> 
> I got the same error for alpha, the same fix applies.

Just trying this patch on Alpha against v3.6-rc1 and it leads to new
compilation errors, namely:

init/init_task.c:12: error: braced-group within expression allowed only
inside a function
init/init_task.c:13: error: braced-group within expression allowed only
inside a function
init/init_task.c:16: error: braced-group within expression allowed only
inside a function
init/init_task.c:16: error: braced-group within expression allowed only
inside a function
make[1]: *** [init/init_task.o] Error 1

> ---
> From: Mel Gorman <mgorman@suse.de>
> Subject: [PATCH] [ALPHA] Redefine ATOMIC_INIT and ATOMIC64_INIT to drop the casts
> 
> The following build error occurred during an alpha build:
> 
> net/core/sock.c:274:36: error: initializer element is not constant
> 
> Dave Anglin says:
>> Here is the line in sock.i:
>>
>> struct static_key memalloc_socks = ((struct static_key) { .enabled >> ((atomic_t) { (0) }) });
> 
> The above line contains two compound literals.  It also uses a designated
> initializer to initialize the field enabled.  A compound literal is not a
> constant expression.
> 
> The location of the above statement isn't fully clear, but if a compound
> literal occurs outside the body of a function, the initializer list must
> consist of constant expressions.
> 
> Reported-by: Fengguang Wu <fengguang.wu@intel.com>
> Signed-off-by: Mel Gorman <mgorman@suse.de>
> Cc: <stable@vger.kernel.org>
> ---
>  arch/alpha/include/asm/atomic.h |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> --- linux.orig/arch/alpha/include/asm/atomic.h	2012-05-24 19:03:06.000000000 +0800
> +++ linux/arch/alpha/include/asm/atomic.h	2012-08-02 23:01:02.243224220 +0800
> @@ -14,8 +14,8 @@
>   */
>  
>  
> -#define ATOMIC_INIT(i)		( (atomic_t) { (i) } )
> -#define ATOMIC64_INIT(i)	( (atomic64_t) { (i) } )
> +#define ATOMIC_INIT(i)		( { (i) } )
> +#define ATOMIC64_INIT(i)	( { (i) } )
>  
>  #define atomic_read(v)		(*(volatile int *)&(v)->counter)
>  #define atomic64_read(v)	(*(volatile long *)&(v)->counter)

Cheers
Michael.