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int lua_getstack (lua_State *L, int level, lua_Debug *ar);
Get information about the interpreter runtime stack.
This function fills parts of a
lua_Debug structure with
an identification of the activation record
of the function executing at a given level.
Level 0 is the current running function,
whereas level n+1 is the function that has called level n.
When there are no errors,
lua_getstack returns 1;
when called with a level greater than the stack depth,
it returns 0.