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kyren
adfeaeab49
Previously, on an internal panic, the Lua stack would be reset before panicking in an attempt to make sure that such panics would not cause stack leaks or leave the stack in an unknown state. Now, such panic handling is done in stack_guard and stack_err_guard instead, and this is for a few reasons: 1) The previous approach did NOT handle user triggered panics that were outside of `rlua`, such as a panic in a ToLua / FromLua implementation. This is especially bad since most other panics would be indicative of an internal bug anyway, so the utility of keeping `rlua` types usable after such panics was questionable. It is much more sensible to ensure that `rlua` types are usable after *user generated* panics. 2) Every entry point into `rlua` should be guarded by a stack_guard or stack_err_guard anyway, so this should restore the Lua stack on exiting back to user code in all cases. 3) The method of stack restoration no longer *clears* the stack, only resets it to what it previously was. This allows us, potentially, to keep values at the beginning of the Lua stack long term and know that panics will not clobber them. There may be a way of dramatically speeding up ref types by using a small static area at the beginning of the stack instead of only the registry, so this may be important.