[Spice-devel] [RFC] QXLDevSurfaceCreate: reorder fields to avoid holes on 64-bit arches.

[Alon Levy]

On Tue, May 22, 2012 at 04:30:33PM +0200, Hans de Goede wrote:
> Hi,
> 
> Why not simply memset the struct to 0 before initializing its fields,
> that should make valgrind happy and is a good idea in general (as it
> puts 0 rather then random crap in fields which you forget to init).

Sure, that works, but it's ugly. Then again all this churn is ugly too.
Lesser evil I guess.

> 
> Regards,
> 
> Hans
> 
> 
> On 05/22/2012 04:27 PM, Alon Levy wrote:
> >The hole remains uninitialized variable when allocating an instance of
> >QXLDevSurfaceCreate on the stack and setting each field individually,
> >producing an uninteresting valgrind warning. The reordering fixes this.
> >It also requires bumping the version of the server.
> >---
> >What's the suggested course here? just ignore this and either add memset in
> >qemu or just pretend I don't see the uninitialized value in valgrind, or push
> >this and what - raise the primary version number (and assume all users actually
> >check for the exact primary and not for a larger then relation..) ?
> >
> >  server/spice.h |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >diff --git a/server/spice.h b/server/spice.h
> >index 77aec92..ef2c6d3 100644
> >--- a/server/spice.h
> >+++ b/server/spice.h
> >@@ -203,6 +203,7 @@ struct QXLDevMemSlot {
> >  };
> >
> >  struct QXLDevSurfaceCreate {
> >+    uint64_t mem;
> >      uint32_t width;
> >      uint32_t height;
> >      int32_t stride;
> >@@ -211,7 +212,6 @@ struct QXLDevSurfaceCreate {
> >      uint32_t mouse_mode;
> >      uint32_t flags;
> >      uint32_t type;
> >-    uint64_t mem;
> >      uint32_t group_id;
> >  };
> >