John Gateley writes: > On Thu, 25 Oct 2007 17:57:11 +0100 > Andrew Haley <aph-gcc@xxxxxxxxxxxxxxxxxxx> wrote: > > > John Gateley writes: > > > I need to compute the offset of a data member at compile time. > > > The class has virtual functions, and so the offsetof macro does > > > not work (why?). > > > > Because it's a non-POD type. See Section 9, Classes: > > > > > Is there a way to do this? > > > > No. Consider what happens with multiple and virtual inheritance. > > > > Thanks for the reply. > > It seems to me that even with multiple > and virtual inheritance, the offset is a compile time constant. > It may be complex to determine it, but it doesn't change. Well, that depends on the implementation. With gcc and other compilers that follow the multi-vendor C++ ABI, things are better-defined than the standard actually requires. So, while what you describe may indeed be possible, it isn't legal ISO C++. Andrew.
