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Date: Thu, 27 Oct 2011 17:18:46 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 1/3] qemu-tls.h: Add abstraction layer
 for TLS variables
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, patches@linaro.org, "Dr. David Alan Gilbert" <david.gilbert@linaro.org>, =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= <afaerber@suse.de>, qemu-devel@nongnu.org

On 10/27/2011 05:15 PM, Peter Maydell wrote:
>
>>> >>  +#define DEFINE_TLS(type, x)  __thread __typeof__(type) tls__##x
>> >  I assume __typeof__() is a GCCism, indicated by ..._GCC_H, to ensure
>> >  type is actually a valid type?
> Paolo?

No, _GCC_H has nothing to do with GCCisms.  __typeof__ is needed so that 
"type" can be "int[5]":

     __thread __typeof__ (int[5]) foo; /* works */
     __thread int[5] foo; /* fails */

(even without __thread of course).

In fact, it has the opposite side effect: type can be any expression, 
but the assumption is that DEFINE_TLS(123, x) will be caught by review.

Paolo