El 19/02/2021 a las 16:54, Andreas Buykx via Boost-users escribió:
I want to use boost::flyweight to capture some structures containing const data.
The documentation states that if flyweights are exported across shared library boundaries that the intermodule holder should be used.
Since my flyweights are all created in the same shared library I would prefer to use the static holder but I keep getting crashes.
It is not only necessary that all flyweights are created in the same DLL: they must also be destroyed within that DLL. I guess that's the problem you're experiencing.
I tried the intermodule holder but I’m having trouble compiling my sources with that.
Can you provide more info on the kind of problems you're running into? intermodule_holder tests successfully in Linux, Mac and Windows platforms. I presume it is Windows you use.
So my thinking was to wrap all flyweight types in accessor classes which are exposed instead, and the accessor classes create the flyweights within the same shared library to store the data. Would that be a valid approach?
I think your first option should be to make intermodule_holder work. That said, the approach you outline below in your mail looks OK, as the lifetime of flyweight objects is handled entirely within DLL-specific exported functions. A simpler approach would be to define a wrapper around boost::flyweight: // template class to be instantiated *only* // within your exporting DLL template<typename T> struct DLLEXPORT dll_flyweight:boost::flyweight<T> { using boost::flyweight<T>::flyweight; };
Also, is it possible to have nested flyweights (when they are wrapped by accessor classes)? And would that cause any additional problems in the above scenario?
I don't see any problem with that. Best, Joaquín M López Muñoz