Re: [Lua5.4] lua_toclose will close the wrong value
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- Subject: Re: [Lua5.4] lua_toclose will close the wrong value
- From: Sean Conner <sean@...>
- Date: 2019年5月21日 13:36:30 -0400
It was thus said that the Great actboy168 once stated:
> #include <lua.h>
> #include <lauxlib.h>
>
> static int close(lua_State *L) {
> return 0;
> }
>
> static void newtable(lua_State *L) {
> static const luaL_Reg mt[] = {
> {"__close", close},
> {NULL, NULL}
> };
> lua_newtable(L);
> luaL_newlib(L, mt);
> lua_setmetatable(L, -2);
> }
>
> int luaopen_toclose(lua_State *L) {
> lua_pushinteger(L, 1);
> newtable(L);
> lua_toclose(L, -1);
> lua_remove(L, -2); // throw error: attempt to close non-closable
> variable '?'
> return 1;
> }
So the flow is:
lua_pushinteger(L,1); // int
lua_newtable(L): // table int
luaL_newlib(L,mt); // table table int
lua_setmetatable(L,-2); // table int
lua_toclose(L,-1); // table int
lua_remove(L,-2); // table
The manual states for lua_toclose():
... the value at that index in the stack will be closed when it goes
out of scope. Here, in the context of a C function, to go out of
scope means that the running function returns to Lua, there is an
error, or the index is removed from the stack through lua_settop or
lua_pop. An index marked as to-be-closed should not be removed from
the stack by any other function in the API except lua_settop or
lua_pop.
This function should not be called for an index that is equal to or
below an already marked to-be-closed index.
Hmm ... the code seems like it should work. Try commenting out the
lua_remove() and see if it works. It might be that moving the item to be
cleaned is disallowed as well and the manual doesn't mention it.
-spc