The code of winsamp.d includes this line:

    assert(RegisterClassA(&wc));

Although at the moment it seems that the assert body is evaluated whether -release is specified or not, this will not be the case in general.  As said, and quite sensibly, "The compiler may optionally not evaluate assert expressions at all."  When the compiler is improved so that assert expressions aren't evaluated in release mode, the class won't be registered at all, and so the program will not work.

The statement should therefore be replaced by

    if (!RegisterClassA(&wc)) assert(false);

or perhaps better

    if (!RegisterClassA(&wc)) throw new Error("RegisterClass failed!");

Stewart.