Re: C++ Plugins and virtual destructors.

[Brendon Costa]

Bob Friesenhahn wrote:
> On Sun, 11 Nov 2007, Daniel Herring wrote:
>>
>> If the vtable is functioning for normal virtual functions, why
>> wouldn't it also work for a virtual destructor?  Destructors are not
>> magic; they are merely functions that get called just before memory is
>> released.  RTTI, a common culprit in dlopen issues, doesn't get
>> involved here.
> 
> Right.  A more important question to ask is if static
> constructors/destructors get properly executed, including the framework
> necessary to support C++ exceptions.  The C++ exception issue is
> significant since usually the framework is set up by the original
> program and if the plugin does not properly mesh into it then there is a
> problem.  There may also be a problem if the program is written and
> linked as a C program but the plugin is C++.
> 

These are annoying issues that I am trying to deal with by avoidance :-)

* The program and plugins are both C++ source linked using the C++
compiler.

* I have avoided static constructors/destructors in the plugins. If i
need to use them which I haven't yet, i will use a singleton pattern
using a static pointer and creation of the singleton in the plugins
initialization routine.

* As for exceptions, I have defined all the methods for the plugins
interface as throw() so exceptions may occur inside the plguin but may
not propagate from the plugin to the application. I honestly dont know
if exceptions occurring only within the plugin may cause any problems?

May i ask what you mean by "properly mesh"? I was un-aware that C++
plugins which might use exceptions need to do anything in order to
make exceptions work (at least internally). It is something I have not
thought about.

Thanks,
Brendon.