Re: [libvirt] [PATCH] uml_conf.c: don't return an uninitialized pointer
On Thu, Sep 03, 2009 at 01:39:25PM +0200, Jim Meyering wrote:
Jim Meyering wrote:
> Daniel P. Berrange wrote:
> ...
>>> Actually I did that first, but then un-did it in favor
>>> of the change above. Why? because that initialization could
>>> mask a failure to initialize in a new case.
>>>
>>> With per-case initialization, we'd detect the bug at
>>> compile/static-analysis time. With the up-front unconditional
>>> initialization, we cannot, and would have to rely on testing to find it.
>>
>> It is a tradeoff, but I still prefer the initialization at time of
>> declaration as a safety net, and we do use this pattern pretty much
>> everywhere
>
> Ok. adjusted
Actually, I will now try to convince you that we should
do it the other way. Not only is it better to have the compiler
tell us about this problem, but if ever someone were to add the
definition that seems to be missing in the default case, clang
would report the preceding initialization (the one you prefer)
as a "dead store" error.
This isn't a dead store though - we are setting the default return
value for cases where there's no explicit return value set. It
would only become a dead store if we also added the redundant
'ret = NULL' initialization that your initial patch did.
In fact, now that I'm looking at what clang calls
dead initializations, I see just such a case in mdns.c:
These are different scenarios dealing with local use
variables only, rather tha default return values as
the above case. Removing these redundant inits makes
sense for mdns/nodedev.
Daniel
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