[pclasses-devel] back to the SharedLib handle problem...

[stephan b. <st...@s1...>]

We could use traits.


template <typename SharedLibImplTag>
HandleTraits
{
	typedef unsigned long handle_type;
}

Inside SharedLib.ltdl.cpp we define the following:


template <>
HandleTraits<lt_handle_t> // or some internal marker type
{
	typedef lt_handle_t handle_type;
}

And in SharedLib's impl we reference _handle via the traits type.

The problem with that is that client code using SharedLib.ltdl only has 
access to HandleTraits's *default* implementation, because the 
specialization must live in hidden impl code. This means that clients 
won't be able to get at the handle in it's native form. This isn't a 
bad thing, but it means that the handle() function in SharedLib.ltdl 
would still need to return the default handle_type. That means that 
we're still basically stuck with not being able to pass the handle back 
to the client properly (currently requires 2 casts: one to void *, then 
one to ulong).
Or we could put the traits types in public headers and #ifdef the proper 
specialization(s) in.

One idea might be making a base class for SharedLib:
	AbstractSharedLib<HandleT>
	SharedLib : public AbstractSharedLib<ulong>
	SharedLibLtDl : public AbstractSharedLib<lt_handle_t>

i don't know if this buys us any flexibility, though.

???

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