While it might be handy to have type-less functionality which is
similar to how C++ math is implemented it can not be easily achieved
with just preprocessor in a way which does not have side-effects on
wrong usage.
There macros where often used on a non-trivial expression, and there
was at least one usage where it was causing an actual side effect/bug
on Windows (see change around square_f(sh[index++]) in studiolight.c).
For such cases it is handy to have a function which is guaranteed to
have zero side-effects. The motivation behind actually removing the
macros is that there is already a way to do similar calculation. Also,
not having such macros is a way to guarantee that its usage is not
changed in a way which have side-effects and that it's not used as an
inspiration for cases where it should not be used.
Differential Revision: https://developer.blender.org/D7051
598ab525da