Re: [Qemu-devel] [PATCH qom v1 1/1] qom/object.c: Split out object and class caches.

[Paolo Bonzini]

Il 28/11/2013 05:27, Peter Crosthwaite ha scritto:
> The object-cast and class-cast caches cannot be shared because class
> caching is conditional on the target type not being an interface and
> object caching is unconditional. Leads to a bug when a class cast
> to an interface follows an object cast to the same interface type:
> 
> FooObject = FOO(obj);
> FooClass = FOO_GET_CLASS(obj);
> 
> Where TYPE_FOO is an interface. The first (object) cast will be
> successful and cache the casting result (i.e. TYPE_FOO will be cached).
> The second (class) cast will then check the shared cast cache
> and register a hit. The issue is, when a class cast hits in the cache
> it just returns a pointer cast of the input class (i.e. the concrete
> class).
> 
> When casting to an interface, the cast itself must return the
> interface class, not the concrete class. The implementation of class
> cast caching already ensures that the returned cast result is only
> a pointer cast before caching. The object cast logic however does
> not have this check.
> 
> Resolve by just splitting the object and class caches.
> 
> Signed-off-by: Peter Crosthwaite <address@hidden>

Cc: address@hidden
Reviewed-by: Paolo Bonzini <address@hidden>