C++ ABI Issues

[Loren James Rittle]

Hi Mark,

> Our testing and investigation has lead to the discovery of several places
> where G++'s class layout still does not match the published ABI
> specification.  Other vendors (notably HP and Intel) do match the ABI
> specification.  Therefore, the ABI specification is probably not going
> to change to validate G++'s behavior. [...]

> I propose that we fix G++ to match the ABI, but that we issue warnings
> about classes whose layout has changed from GCC 3.2.

This sounds quite reasonable to me.  However, this will be quite
annoying in practice, if e.g. libstdc++-v3 exposes something that
triggers issue 2 (I'm fairly sure that it will not trigger issue 1).

> If we are going to fix G++, we also have to decide how urgently to do
> another release.

Seems that low-level C++ ABI issues should be fixed sooner rather than
later now that we claim to adhere to a multi-vendor standard.

Regards,
Loren