Mail Archives: cygwin/1999/12/18/00:51:39
On Fri, 17 Dec 1999 gschmidt AT BUNSEN-AND-BEAKER DOT MIT DOT EDU wrote:
> dllimport'd virtual function members aren't correctly handled
> currently -- the compiler chokes when it tries to generate the vtable.
> That's not a disaster, because unlike data, functions don't have to be
> declared dllimport for them to be correctly imported.
>
> I posted a workaround patch for this to the list earlier, and some
> others with more gcc internals clue than myself are working on a
> cleaner and more efficient solution.
I'll have an "update" for gcc-2.95.2 that will fix quite a few of the
known bugs in importing and exporting C++ methods (and C functions).
The method actually is somewhat similar, at least in spirit, to the
change Geoff had suggested in gcc mailing list.
The gotcha in my update will be the following:
- C++ methods will still use the thunks. Not a big deal.
- Still won't be able to erroneous code like the one this bug report
was about (trying to *define* a dll imported method). Even MSVC
warns about this, and this behaviour IMO can lead to buggy code
that is hard to track down.
- lots of extra vtables generated, which makes the executable larger
than say what MSVC will produce.
What we're trying to do for gcc-2.96 is more ambitious -- trying to
match what MSVC does. However, as I keep on finding out, this requires
quite a few tricky changes to the C++ front-end to make certain bits
of information available earlier so that dllimport/export code use it.
This is turning out to be not so easy. Fingers crossed. Thanks to Jason
Merrill (C++ co-maintainer) for taking a look at this issue. C++ front-
end is hairy, privy to only a handful of folks out there and I certainly
am not one of those. Not even by a long shot!
I do hope that users will hold on for a while and we will fix these over
time (contingent upon how much of our free time we're willing to devote
to it of course).
Regards,
Mumit
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