rob wrote: > Using Lua, lua_tostring returns string pointers and a null pointer > if the given index in the stack does not exist, e.g. -1 when a > registered C function passes no arguments from Lua. There's a difference between 'acceptable' and 'valid' stack indexes. Please check the Lua 5.1 manual, section 3.1 and 3.2. Your use of index -1 with no arguments on stack is not ok -- you're relying on undefined behavior. In fact, it'd trigger an assertion from the plain Lua VM (if you had enabled them). > Is there a way to check if a given stack index is empty, i.e. there > is no passed value, or have a null pointer returned? Use lua_isnone() with an acceptable index, e.g. +1 for the first argument. --Mike