Re: [libvirt] [PATCHv4 2/4] Allow <source> for type=block to have no dev
On 09/16/2013 02:20 PM, Doug Goldstein wrote:
>> case VIR_DOMAIN_DISK_TYPE_BLOCK:
>> - virBufferEscapeString(buf, " <source
dev='%s'",
>> - def->src);
>
> If def->src is NULL, this is a no-op, rather than printing def='(null)'.
> Are you sure your commit message is accurate?
The (null) was assumed based on my knowledge of gnulib's *printf
helpers. So I guess the commit message was wrong.
virBufferEscapeString() intentionally avoids calling printf for a NULL
string - but had we reached printf, you are right that glibc would print
"(null)" (and other libc's might SEGV).
>
>> + virBufferAddLit(buf, " <source");
>> + if (def->src)
>> + virBufferEscapeString(buf, " dev='%s'",
def->src);
>
> The 'if' is unnecessary; virBufferEscapeString is a no-op for a NULL
> argument. However, you are correct that we MUST output "<source"
> independently from def->src being NULL, otherwise..
A lot of this file does if checks for NULL of the parameters. It seems
like we could clean it up a bit with that condition.
Yeah, probably a lot of those places that we can clean. So far, we've
been doing it piece-wise as we come across places that are touched for
other reasons.
>
>> if (def->startupPolicy)
>> virBufferEscapeString(buf, "
startupPolicy='%s'",
>> startupPolicy);
>
> printing the startupPolicy generates invalid XML. Another
> (pre-existing) case of an unnecessary 'if'.
>
So you're saying that <source startupPolicy='optional'/> is invalid
XML? Or something else?
For NULL def->src and non-null startupPolicy, the old code would produce:
" startupPolicy='...'"
and the new code produces
"<source startupPolicy='...'"
Basically, your patch separates the data that must always be printed
("<source") from the data that is conditional ("
dev='...'").
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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