snapshot of Lua 4.1 (work) problems with VC++

["Peter Loveday" <peter@...>]

Thanks for giving us access to this in-progress version!

I've found a bit of a problem compiling it for windows. (with VC++ sp5)

This seems to be due to an obscure bug in the Microsoft pre-processor,
which gets upset with substitution of the G(L) macro from within the
(new) cast(t,x) macro.

For example, the code in lgc.c in checkMbuffer()

luaM_reallocvector(L, G(L)->Mbuffer, G(L)->Mbuffsize, newsize, l_char);

where luaM_reallocvector() uses cast() a few times, seems to make the
preprocessor attempt to substitute the member variable G (from L->G) as
a macro instead of treating it as a variable.  This of course causes
it to get the code completly wrong.

The Intel compiler for VC++ does not have this problem, and while it is
clearly a microsoft bug, in the interests of compatibility perhaps something
could be done.  The true cause of this problem seems to stem from the
fact the macro G(L) has the same name as the member variable 'G' in Lua_state.

If either were renamed then the problem would no longer exist; and in general
I'd say having defines and variables (or members) of the same name is probably
best avoided, even if the macro does require an arg in this case.

Thanks for your time!

Love, Light and Peace,
- Peter Loveday