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Re: [Libguestfs] [PATCH nbdkit] server: Remove tricksy initialization of struct b_conn_handle.

On 9/19/19 7:56 AM, Richard W.M. Jones wrote:
> b_conn_handle fields exportsize and can_* have a special meaning when
> they are -1.  It means that the value of the field has not been
> computed and cached yet.
> The struct was being initialized using memset (_, -1, _) which does
> indeed have the effect of setting all the fields to -1, although it's
> somewhat non-obvious to say the least.
> This commit replaces it with ordinary field initialization, also
> setting h->handle to NULL.  By keeping the initialization function
> next to the struct definition, hopefully they will be updated in
> tandem in future.
> GCC 9.2.1 actually optimizes this back into the memset equivalent
> using inline AVX instructions, so good job there!
> Simple refactoring, should have no effect on how the code works.
> See commit d60d0f4248610fc1d116dc9f249526d20913c9a3.

ACK. And affects 3 and 4 of my pending spec cleanup patches, but yours
should go in first (I'll rebase mine, because I'm working on refactoring
those for less code duplication anyway).

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

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