From: Florian Grafenberg (florian-grafenberg_at_[hidden])
Date: 2004-08-03 10:44:47
Hi boosters,
I developed a fairly simple prototype of a dll loader which mangles
functions names automatically. But there are limitiations: you cannot
call function which have template class parameters or return value, e.g.
void test(std::string const &str) will not work. I do not get the
mangling scheme used to decorate such a type, maybe someone knows a good
source where I can look that up?!
For class mangling I use the string returned by type_info::name(), but
that seems very hacky. Microsoft Visual C++ does not always return
correct strings (e.g. typeid(int &).name() returns "int").
Sorry that I attached the source code to that mail as I know that only a
few will look at it, but I don't have a homepage handy to upload it there.
- nico
> Vladimir Prus wrote:
>
>> Reece Dunn wrote:
>> >>I also wonder if it makes sense to sumbit just "dll" library, or some
>> >>additional plugin support need to be developed first.
>> >
>> > What sort of plugin support are you looking for? Do you mean something
>> > like COM/CORBA support or wrapper, e.g. something that can target both
>> > (and others like them) in one implementation?
>>
>> I'm not CORBA expert, but I think it's entirely different beast. To use
>> CORBA object you use stub generated from IDL, how it's related to
>> plugins?
>> While there are some ways to find object dynamically, it's different
>> mechanism from shared libraries, isn't it?
>
>
> I am not sure how CORBA works. COM generally uses a different
> mechanism to load COM objects via CoCreateInstance, although DirectX
> exposes creation functions that circumvent this. I was thinking about
> being able to use COM/CORBA as a platform for object lifetime and dll
> lifetime management (as well as things like interface extension, etc.).
>
>> I though more about at least some kind of map<string, BasePlugin*>
>> which is
>> updated automatically when you load new DLLs.
>
>
> So the dll implements some function:
>
> __declspec(dllexport) BasePlugin * GetMyPlugin();
>
> so you can do something like:
>
> void load_plugins( map< string, BasePlugin * > & pi )
> {
> for( map< string, BasePlugin * >::iterator i = pi.begin(); i !=
> pi.end(); ++i )
> {
> boost::dll plugin(( *i ).first );
> ( *i ).second = plugin.import< ... >( "GetMyPlugin" );
> }
> }
>
> It is possible to keep the DLL in memory until all instances of a
> class (or set of classes) by incrementing/decrementing a global object
> count variable on construction/deconstruction as is done when using
> COM. You then check this variable in the DllCanUnload function.
>
> You may need some reference counting mechanism to keep the plugin
> alive, but this is not necessary if you load all plugins on startup
> and release them at the end of the run.
>
> It should be possible to implement these facilities in a library, e.g.:
>
> class object_counter
> {
> private:
> static int objectCount = 0;
> public:
> inline int get_object_count(){ return( objectCount ); }
> public:
> inline object_counter(){ ++objectCount; } // make MT aware
> inline ~object_counter(){ --objectCount; } // make MT aware
> };
>
> class reference_counter
> {
> private:
> int refCount;
> public:
> inline void add_ref(){ ++refCount; } // make MT aware
> inline void dec_ref()
> {
> if( --refCount == 0 ) // make MT aware
> {
> delete this;
> }
> }
> public:
> inline reference_counter( int rc ): refCount( rc ){}
> inline ~reference_counter(){}
> };
>
> allowing:
>
> class plugin: public object_counter, public reference_counter, public
> BasePlugin
> {
> // ...
> };
>
> __declspec(dllexport) BOOL DllCanUnload()
> {
> return( object_counter::get_object_count() == 0 );
> }
>
> I'm not sure what the Linux equivalent would be.
>
> Regards,
> Reece
>
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