Be careful using GUI specifiers before class declarations; they can be ambiguous. Any ambiguities must be resolvable at compile-time.
// bad style:
msw winclass myclass
mswnt winclass myclass
window myclass inst // Ambiguous. Is it an instance of
// the msw class or the mswnt class?
The preceding example’s ambiguity can be resolved by specifying a GUI target with conditional compilation (so that, for example, only code for msw gets compiled, in which case inst would be an instance of the msw class or by explicitly using a GUI specifier for the window, as follows:
// good style: msw winclass myclass mswnt winclass myclass msw window myclass inst