Re: On the cost of libraries

[Colm Smyth <Colm Smyth sun com>]

>From: Drazen Kacar <dave willfork com>
>To: Colm Smyth <Colm Smyth sun com>
>
>Colm Smyth wrote:
>> >> It can also be quite handy when trying to resolve
>> >> nasty problems, for example when trying to combine
>> >> two libraries that each expect to be able to override
>> >> the C++ global new() operator, you can specify a different
>> >> "global" new() symbol binding for each library!
>> >
>> >Uh... I think this would backfire sooner or later. How about using -B group
>> >or -z groupperm instead?
>> 
>> Why do you think it would backfire? You can't get more explicit than
>> actually stating precisely the library that contains a symbol
>> definition.
>
>Yeah, but... I don't know what would happen if the next installed version
>of that library (binary compatible) just happens not to contain that
>particular symbol. Nothing good, I presume. C++ is not my area and this
>particular example might be safe for all I know. But in general I would
>try to be very cautious with things like that.

Binary compatibility is an important goal, but with C++ it's effectively
impossible; the name-mangling format changes not infrequently, vtable dispatch
is also subject to change.  The upshot is that the ABI of a C++ library can
change between minor version updates so the usage scenario I described is
applicable only when you are targetting a well-known C++ ABI.

Colm.

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