In the code, lua_assert, lua_lock, and lua_unlock are defined as (void)0, which is essentially a no-op. Why?

It's because:

• Vanilla Lua is pure ANSI C and runs on a single thread. So we don't need lock and unlock.
• Lua is designed to be ported to many different platforms. Porters can customize the behavior of Lua by overriding these macros. For example, you might need some form of GIL like Python if you want multi-threading.

You need to implement your own assert mechanism if you want to debug the internal of Lua

• https://stackoverflow.com/questions/3010974/purpose-of-lua-lock-and-lua-unlock