Re: [Qemu-block] [Qemu-devel] [PATCH 03/12] block: Introduce BlockBackendPublic

[Kevin Wolf]

Am 23.03.2016 um 22:35 hat Eric Blake geschrieben:
> On 03/23/2016 03:09 AM, Kevin Wolf wrote:
> >>> +++ b/block/block-backend.c
> >>> @@ -33,6 +33,7 @@ struct BlockBackend {
> >>>      DriveInfo *legacy_dinfo;    /* null unless created by drive_new() */
> >>>      QTAILQ_ENTRY(BlockBackend) link;         /* for block_backends */
> >>>      QTAILQ_ENTRY(BlockBackend) monitor_link; /* for 
> >>> monitor_block_backends */
> >>> +    BlockBackendPublic public;
> >>
> >> Any reason to not put the public struct at offset 0?
> > 
> > No, but also no reason to put it there. :-)
> 
> True.
> 
> >>> +typedef struct BlockBackendPublic {
> >>> +} BlockBackendPublic;
> >>
> >> No fields?  So really all we need this for is so that we can have an
> >> address of a member of the larger struct, so that we can do list
> >> operations based on that address?
> > 
> > Well, a list still needs a QLIST_ENTRY, otherwise I could have directly
> > used BlockBackend. I just tried to keep the introduction of .public
> > separate from the addition of a specific list.
> > 
> > I think it's strictly speaking invalid C to have an empty struct, but
> > gcc compiles it and so I thought it should be acceptable to have one for
> > a single commit until something is added there.
> 
> clang gripes; see commit 83ecb22ba.
> 
> But breaking bisection for one patch on clang-only is different than
> breaking bisection on all compilers, so up to you what you want to do
> about it.

We can always have an int dummy in there...

Kevin

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