Re: [PATCH 16/52] migration/rdma: Fix io_writev(), io_readv() methods to obey contract

[Fabiano Rosas]

Markus Armbruster <armbru@redhat.com> writes:

> QIOChannelClass methods qio_channel_rdma_readv() and
> qio_channel_rdma_writev() violate their method contract when
> rdma->error_state is non-zero:
>
> 1. They return whatever is in rdma->error_state then.  Only -1 will be
>    fine.  -2 will be misinterpreted as "would block".  Anything less
>    than -2 isn't defined in the contract.  A positive value would be
>    misinterpreted as success, but I believe that's not actually
>    possible.
>
> 2. They neglect to set an error then.  If something up the call stack
>    dereferences the error when failure is returned, it will crash.  If
>    it ignores the return value and checks the error instead, it will
>    miss the error.
>
> Crap like this happens when return statements hide in macros,
> especially when their uses are far away from the definition.
>
> I elected not to investigate how callers are impacted.
>
> Expand the two bad macro uses, so we can set an error and return -1.
> The next commit will then get rid of the macro altogether.
>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>

Reviewed-by: Fabiano Rosas <farosas@suse.de>