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Date: Fri, 11 Apr 2014 15:48:02 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] qapi-commands.py generates code that uses
 uninitialized variables
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Markus Armbruster <armbru@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, Anthony Liguori <aliguori@amazon.com>, Michael Roth <mdroth@linux.vnet.ibm.com>

On Fri, 04/11 08:27, Peter Maydell wrote:
> On 11 April 2014 02:40, Eric Blake <eblake@redhat.com> wrote:
> > We uncovered a real bug that would be fixed by this patch:
> > https://lists.gnu.org/archive/html/qemu-devel/2014-04/msg01745.html
> 
> No, that's a bug in the called code. The API here defines
> that for optional parameters, if the have_foo bool is false
> then the foo argument isn't set. The generated code
> can't know the correct default value (it just happens
> to be 0 in the case you point out, but what if the default
> speed were 100?) so this must be handled by the called
> code.
> 

Default value for a variable isn't default value for API logic, so apparently
called code must always handle both have_foo and foo. But there is a point to
take this patch from the language perspective, to avoid that an unset variable
is passed as a parameter from generated code.

Thanks,
Fam