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Date: Fri, 30 Oct 2009 02:25:33 +0000
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] Re: [PATCH 2/7] Introduce QError
Message-ID: <20091030022533.GC20292@shareable.org>
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, Anthony Liguori <aliguori@us.ibm.com>, kraxel@redhat.com, hollisb@linux.vnet.ibm.com, Luiz Capitulino <lcapitulino@redhat.com>

Paolo Bonzini wrote:
> On 10/29/2009 09:48 PM, Luiz Capitulino wrote:
> >>  va_list doesn't need to be a pointer.
> >
> >  Ok, but if this is going to be a public interface, I think it's
> >better to va_copy() before passing it to qobject_from_json_va() then.
> 
> It is standard to pass a va_list by value without doing va_copy in the 
> caller.

That's right, just like:

    va_list ap;
    va_start(ap, format);
    vfprintf(stderr, format, ap);   /* <- passed by value */
    va_end(ap);

You only need va_copy() is you're going to use some more it after
passing it to the function.

There should be one va_end() for every va_start() plus every va_copy().

-- Jamie