Before calling a finalizer, Lua not only checks stack limits, but
actually ensures that a minimum number of slots are already allocated
for the call. (If it cannot ensure that, it postpones the finalizer.)
That avoids finalizers not running due to memory errors that the
programmer cannot control.
New function 'resetCI' resets the CallInfo list of a thread, ensuring
a proper state when creating a new thread, closing a thread, or
closing a state, so that we can run code after that. (When closing a
thread, we need to run its __close metamethods; when closing a
state, we need to run its __close metamethods and its finalizers.)
This function can be called unprotected, so it should not raise any
kind of errors. (It could raise a memory-allocation error when creating
a message).
Several definitions that don't need to be "global" (that is, that
concerns only specific parts of the code) moved out of llimits.h,
to more appropriate places.
The generational mode also uses the parameters for the incremental
mode in its major collections, so it should be easy to change those
parameters without having to change the GC mode.
'lua_resetthread' is back to its original signature, to avoid
incompatibilities in the ABI between releases of the same version.
New function 'lua_closethread' added with the "correct" signature.
When closing variables during 'coroutine.close' or 'lua_resetthread',
the status of a coroutine must be set to LUA_OK; a coroutine should
not run with any other status. (See assertion in 'lua_callk'.)
After the reset, the status should be kept as normal, as any error
was already reported.
Instead of assuming that shrinking a block may be an emergency
collection, use an explicit field ('gcstopem') to stop emergency
collections while GC is working.
More uses of macros 'likely'/'unlikely' (renamed to
'l_likely'/'l_unlikely'), both in range (extended to the
libraries) and in scope (extended to hooks, stack growth).
To-be-closed variables are linked in their own list, embedded into the
stack elements. (Due to alignment, this information does not change
the size of the stack elements in most architectures.) This new list
does not produce garbage and avoids memory errors when creating tbc
variables.
Initial implementation to allow yields inside '__close' metamethods.
This current version still does not allow a '__close' metamethod
to yield when called due to an error. '__close' metamethods from
C functions also are not allowed to yield.
