Re: [Xen-devel] [PATCH v3 07/10] xen/nodemask: Drop nodes_{setall, clear}() and improve the initialisers

From: Jan Beulich <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: StefanoStabellini <sstabellini@kernel.org>,
	"Wei Liu" <wl@xen.org>, "Julien Grall" <julien.grall@arm.com>,
	Xen-devel <xen-devel@lists.xenproject.org>,
	"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v3 07/10] xen/nodemask: Drop nodes_{setall, clear}() and improve the initialisers
Date: Wed, 31 Jul 2019 13:12:46 +0000	[thread overview]
Message-ID: <0ec79656-2132-441e-99c6-2fcfb842ff99@suse.com> (raw)
In-Reply-To: <88cead08-46ab-7623-c01a-adfd7267e9e1@citrix.com>

On 31.07.2019 14:49, Andrew Cooper wrote:
> I don't see a way to avoid expanding node twice, but given that its wrapper is in ALL_CAPS and obviously a macro.
> 
> Furthermore, experimenting with a deliberate attempt to provoke this, I got
> 
> numa.c: In function ‘numa_initmem_init’:
> 
> /local/xen.git/xen/include/xen/nodemask.h:90:10: error: nonconstant array index in initializer
> 
>           [(node) / BITS_PER_LONG] = 1UL << ((node) % BITS_PER_LONG)      \
> 
>            ^
> 
> numa.c:274:23: note: in expansion of macro ‘NODEMASK_OF’
> 
>       node_online_map = NODEMASK_OF(foo++);
> 
>                         ^~~~~~~~~~~
> 
> /local/xen.git/xen/include/xen/nodemask.h:90:10: note: (near initialization for ‘(anonymous).bits’)
> 
>           [(node) / BITS_PER_LONG] = 1UL << ((node) % BITS_PER_LONG)      \
> 
>            ^
> 
> numa.c:274:23: note: in expansion of macro ‘NODEMASK_OF’
> 
>       node_online_map = NODEMASK_OF(foo++);
> 
>                         ^~~~~~~~~~~
> 
> from GCC 6.3, which I think covers everything we need, and will prevent side effects from double expansion in practice.

Ah, right. With this my R-b applies to the change as is (with the
additional adjustments folded in that you've pointed out).

Jan
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