Hi Ahmed,
I just installed Visual Studio 2017 on my Windows 10 machine, downloaded the latest glib, glib-dev, pkg-config, proxy-libintl and gettext, copied the ladspa.h file into the VS include dir and ran cmake. Then I built the project and ran fluidsynth.
I could load a LADSPA plugin compiled for Win64 and hear the effects. So it seems to work... can you give more details about the error you are encountering?
Also, the "void function returns a value" are due to a recent change in master which I've incorporated into the ladspa branch. There's a discussion in the relevant commit on GitHub:
All the best,
Marcus