[cfe-dev] COM ABI support?

[Csaba Raduly]

Hi Stephen,

On Fri, Jul 12, 2013 at 5:39 PM, Stephen Lin  wrote:
>> Some don't. IBM's C/Set++ or the VisualAge C++ compiler for OS/2
>> didn't (the pointers in the vtable were 8 bytes apart, despite it
>> being a 32-bit compiler). Our (cross-platform: Windoes, OS/2, Mac,
>> Unix, NetWare, ...) product had a library with a COM wrapper on it.
>> All platforms implemented COM in C++, except OS/2, where we had to use
>> plain C to get the correct layout.
>
> Out of curiosity, what were the extra 4 bytes in each vtable entry
> for? Was this part of some implementation strategy to support
> pointers-to-member-functions, or something like that?

I have no idea. It's been over ten years ago, and I didn't investigate
at the time; it was just an "odd thing".

Csaba
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