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Date: Sun, 12 Oct 2008 13:10:51 -0600 (MDT)
Message-Id: <20081012.131051.-345488819.imp@bsdimp.com>
Subject: Re: [Qemu-devel] [5466] Only use __builtin_* with GCC >= 3.4
From: "M. Warner Losh" <imp@bsdimp.com>
In-Reply-To: <48F21193.3000809@redhat.com>
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To: qemu-devel@nongnu.org, avi@redhat.com

In message: <48F21193.3000809@redhat.com>
            Avi Kivity <avi@redhat.com> writes:
: Jamie Lokier wrote:
: > Glibc uses "#if __GNUC_PREREQ (3,4)" which is quite neat.
: > Do "grep -R GNUC_PREREQ /usr/include".
: >
: > I use (and define if not already defined) the same macro in my
: > programs, on the assumption that the macro's meaning is unlikely to
: > ever change or be different elsewhere.
: >   
: 
: It's illegal to define or use an identifier beginning with two 
: underscores, unless it's documented by the implementation.  What if 
: glibc adds a third argument?  All your apps wil break.

Lots of things would break :-(

: You should define your own macros for this, with a non-__ name.

Identifiers starting with __ are reserved for the implementation.
They aren't illegal, per se, just reserved.

Warner