Hi,
On Tue, 2005-08-02 at 16:55 -0500, Patrick Hartling wrote:
> After a long, frustrating afternoon of debugging, I have discovered
> something peculiar when trying to use a member function from a class with
> multiple bases as the functor for OSG::traverse(). I use
> OSG::osgTypedMethodFunctor1ObjPtrCPtrRef<...>() to create the functor that
> is handed off to OSG::traverse(), and up until now this has worked fine.
> When using Visual C++ 7.1 and a class that uses multiple inheritance,
> however, the OSG::FunctorBase<T>::_flags data member is trashed in the call
> to OSG::TypedStoredObjectFunctorBase<...>::setMethod() because the storage
> for the OSG::FunctorBase<T>::_data2 member is not large enough. Only four
> bytes are allocated, but eight are required.
>
> The tricky thing is that this only appears to happen with Visual C++ 7.1 and
> a class that uses multiple inheritance. The attached program demonstrates
> the behavior. When compiled with Visual C++ 7.1, sizeof(&A::f) returns 4
> whereas sizeof(&B::f) returns 8. With GCC 3.4 (tested on Fedora Core 3) and
> 4.0 (tested on Mac OS X 10.4.2), both return 8.
>
> It is probably possible for me to work around this behavior by passing an
> alternate type for the SizeTraitsT template parameter to
> OSG::FunctorBase<T>, though I have not tried doing so yet. I do not know if
> there is a solution that OpenSG can use to account for this case, but if I
> come up with one, I will submit a patch.
there should be an easy fix, basically one has to change the way the
sizes are calculated.
Right now OpenSG only takes the maximum of either function or method
pointer with no inheritance. Checking the size of method functors with
multiple inheritance should not be a too big problem.
could you try to use if the following helps (I don't have windows to
try)
struct DefaultFunctorSizeTraits
{
struct Base {};
struct Base1 {};
struct Derived : public Base, public Base1 {};
typedef
void ( *FuncPointerT )(void *);
typedef
void (DefaultFunctorSizeTraits::*InstanceFuncPointerT)(void *);
typedef
void (Derived ::*MethodFuncPointerT)(void *);
enum SizesE
{
_uiFuncPointerSize1 = osgStaticMax<sizeof(FuncPointerT),
sizeof(InstanceFuncPointerT)
>::iMax,
_uiFuncPointerSize = osgStaticMax<_uiFuncPointerSize1,
sizeof(MethodFuncPointerT)
>::iMax,
_uiObjectSize = 64
};
};
gerrit
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