I never liked the various hacks I had come up with for representing
resource handles in Ruamoko. Structs with an int were awkward to test,
pointers and ints could be modified, etc etc. The new @handle keyword (@
used to keep handle free for use) works just like struct, union and
enum in syntax, but creates an opaque type suitable for a 32-bit handle.
The backing type is a function so v6 progs can use it without (all the
necessary opcodes exist) and no modifications were needed for
type-checking in binary expressions, but only assignment and comparisons
are supported, and (of course) nil. Tested using cbuf_t and QFile: seems
to work as desired.
I had considered 64-bit handles, but really, if more than 4G resource
objects are needed, I'm not sure QF can handle the game. However, that
limit is per resource manager, not total.
Empty structs are now (correctly) invalid. The hack of using an empty
struct to represent a handle returned from a builtin has been unnecessary
since opaque structs were implemented: now a pointer to an opaque struct
can be used. This is mostly safe as handles are aways negative and thus
attempting to dereference such a pointer should result in a VM error. It
will be even safer once const is implemented and the pointers can be made
constant (eg, typedef struct handle * const handle;)
