lua_Hook

lua_Hook

typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);

Type for debugging hook functions.

Whenever a hook is called, its ar argument has its field event set to the specific event that triggered the hook. Lua identifies these events with the following constants: LUA_HOOKCALL, LUA_HOOKRET, LUA_HOOKTAILCALL, LUA_HOOKLINE, and LUA_HOOKCOUNT. Moreover, for line events, the field currentline is also set. To get the value of any other field in ar, the hook must call lua_getinfo.

For call events, event can be LUA_HOOKCALL, the normal value, or LUA_HOOKTAILCALL, for a tail call; in this case, there will be no corresponding return event.

While Lua is running a hook, it disables other calls to hooks. Therefore, if a hook calls back Lua to execute a function or a chunk, this execution occurs without any calls to hooks.

Hook functions cannot have continuations, that is, they cannot call lua_yieldk, lua_pcallk, or lua_callk with a non-null k.

Hook functions can yield under the following conditions: Only count and line events can yield; to yield, a hook function must finish its execution calling lua_yield with nresults equal to zero (that is, with no values).