> is Lua still write in the subset of C89 and C++03?Yes. If you compile with LUA_ANSI defined, it will not use long long.
Sure. The idea is that the default would be 64-64, but restricted systems
> but the issue is the integer wide of Lua: can Lua use different standard
> integer on different system?
probably will prefer 32-32. (Moreover, systems with no 64-bit integers
at all can use either 32-32 or 32-64).
Currently, the problem is even worse, as many people use Lua without
floating-point numbers. Mostly, we just ignore those uses (it is not
"official" Lua) and pretend the problem does not exist. We hope the
32-32 option will allow many programmers in embedded systems to have
a non-standard but officialy supported version of Lua, with 32-bit
integers for performance and floating-point numbers when necessary.