[Libguestfs] [libnbd PATCH] lib: Consolidate free callbacks to just happen at retire time

[Eric Blake]

On 8/15/19 5:22 AM, Richard W.M. Jones wrote:
> On Wed, Aug 14, 2019 at 05:38:31PM -0500, Eric Blake wrote:
>> When we introduced valid_flags, there was an incentive to do as few
>> callbacks as possible, favoring cb(VALID|FREE) calls over the sequence
>> cb(VALID);cb(FREE).  To make it work, we set .callback=NULL after an
>> early free, so that the later check during retirement didn't free
>> again.
>>
>> But now that our .free callback is distinct from our other callbacks,
>> there is no longer an advantage to bundling things, and a significant
>> reduction in lines of code by just doing it in one place.  This
>> basically reverts 9c8fccdf (which had slightly-questionable C
>> type-punning anyway) and 57150880.
> 
> I didn't see this one before implementing an alternate version here:
> 
> https://www.redhat.com/archives/libguestfs/2019-August/msg00251.html
> https://www.redhat.com/archives/libguestfs/2019-August/msg00253.html
> 
> They're fairly similar, but I didn't get rid of the FREE_CALLBACK
> macro for reasons which are clearer later in the series.

Yeah, having looked at yours, you got rid of the type-punning but added
more convenience macros instead of dropping them; I'm fine with yours.

Good to know we were thinking on the same lines :)

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 488 bytes
Desc: OpenPGP digital signature
URL: <http://listman.redhat.com/archives/libguestfs/attachments/20190815/bb05c90e/attachment.sig>