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Re: [libvirt] [PATCH v3 4/4] bridge driver: don't masquerade local subnet broadcast/multicast packets



On 09/24/2013 07:23 AM, Laszlo Ersek wrote:

>>> +
>>> +    localMulticast->prefix = 24;
>>> +    result = virSocketAddrParseIPv4(&localMulticast->addr,
>>> +                                    "224.0.0.0");
>>> +    sa_assert(result != -1);
>>
>> You must have accidentally left this in. libvirt is a library, so it
>> must never assert. In a case where the called function is guaranteed to
>> never fail (due to the args passed in), you can enclose it in
>> ignore_value():

Libraries must NOT use assert().  But libvirt MAY use sa_assert() -
which exists only as a hint to shut up puny static analyzers and NOT as
a way to abort execution if the constraint is violated (of course, if
the constraint is violated, we still have a bug that needs fixing...).

>>
>>      ignore_value(cirSocketAddrParseIPv4(.......)
> 
> Ah. Good to know!
> 
> In fact I had searched the HACKING file for "assert", and there were no
> hits. So I grepped the source :)

We have uses of assert() in tools/virsh*.c, but only because virsh is an
end-user executable, and not a library.  But you are correct that we
must NOT have it within daemon/ or src/.  And indeed, ignore_value() is
a nice way to declare that we know our particular call isn't worth
checking for failure.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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