[Scummvm-devel] Porting headaches

[Jamieson Christian]

----- Original Message ----- 
From: "Arisme" <arisme at free.fr>
Sent: Monday, December 08, 2003 4:56 PM


I'm having some troubles with one very tiny part of the code, in dialogs.cpp
where misc functions from GUI::OptionsDialog are called from
Scumm::OptionsDialog
-------------------------------------------------------

This is also a problem in MSVC6. The PocketMatrix post recommending
reinterpret_cast<>, however, does not sound like the best solution.
reinterpret_cast is the most dangerous casting operator to use because it
simply reinterprets your pointer as being of a different type, without any
appropriate transformations. My understanding of vtables (which is limited)
is that interpreting a derived class pointer as a base class pointer will
actually mean a pointer with a slightly different value, to point to a new
vtable at the very least.

Since GUI::OptionsDialog is a base class of Scumm::OptionsDialog, you should
simply be able to do a conventional typecast:

    ((GUI::OptionsDialog*)this)->open();

This at least compiled on MSVC6 (changing, also, the ::close() and
::handleCommand() calls). If I can ever get the damn thing to finish
compiling and linking everything else (damn BS2 code!), I can see if it
works in runtime.

If the above does not work, a static_cast<> is still preferable to a
reinterpret_cast<>. Fingolfin would be able to provide more details on this.
I think he probably wrote the original code anyway?

(Well, just finished trying to link once again, and a whole bunch of other
crap is broken as well, so I won't be able to test run-time behavior just
now. Sorry.)

    -- Jamieson (sf.net: Jamieson630)