Function GCTM

depends/lua/src/lgc.c:807–838

static void GCTM (lua_State *L, int propagateerrors) {
  global_State *g = G(L);
  const TValue *tm;
  TValue v;
  setgcovalue(L, &v, udata2finalize(g));
  tm = luaT_gettmbyobj(L, &v, TM_GC);
  if (tm != NULL && ttisfunction(tm)) {  /* is there a finalizer? */
    int status;
    lu_byte oldah = L->allowhook;
    int running  = g->gcrunning;
    L->allowhook = 0;  /* stop debug hooks during GC metamethod */
    g->gcrunning = 0;  /* avoid GC steps */
    setobj2s(L, L->top, tm);  /* push finalizer... */
    setobj2s(L, L->top + 1, &v);  /* ... and its argument */
    L->top += 2;  /* and (next line) call the finalizer */
    L->ci->callstatus |= CIST_FIN;  /* will run a finalizer */
    status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0);
    L->ci->callstatus &= ~CIST_FIN;  /* not running a finalizer anymore */
    L->allowhook = oldah;  /* restore hooks */
    g->gcrunning = running;  /* restore state */
    if (status != LUA_OK && propagateerrors) {  /* error while running __gc? */
      if (status == LUA_ERRRUN) {  /* is there an error object? */
        const char *msg = (ttisstring(L->top - 1))
                            ? svalue(L->top - 1)
                            : "no message";
        luaO_pushfstring(L, "error in __gc metamethod (%s)", msg);
        status = LUA_ERRGCMM;  /* error in __gc metamethod */
      }
      luaD_throw(L, status);  /* re-throw error */
    }
  }
}


/*