Because Lua is an embedded extension language, all Lua actions start from C code in the host program calling a function from the Lua library (see lua_pcall). Whenever an error occurs during Lua compilation or execution, control returns to C, which can take appropriate measures (such as printing an error message).

Lua code can explicitly generate an error by calling the error (message [, level]) function. If you need to catch errors in Lua, you can use the pcall (f, arg1, ...) function.