[tarantool-patches] Re: [PATCH v7 1/6] lua: remove exceptions from function luaL_tofield()

[Konstantin Osipov <kostja@tarantool.org>]

* Vladislav Shpilevoy <v.shpilevoy@tarantool.org> [19/01/16 21:29]:

I don't mind if we have a cpcall even in scope of this patch - but
let's test these errors, not just rewrite the code and hope for
the best. 

Can we have any kind of test which runs in short time for lua
errors?
























































> 3. In my opinion there is still a problem with lua_* methods,
> throwing exceptions on OOM *and on a simple stack overflow*.
> Even fixed GC will not fix the problem if all memory is
> occupied by non-garbage memory. I adhere to my opinion that it
> is better to use lua_cpcall. There is nothing bad with it. *_pcall
> just remembers a couple of registers, it is not too expensive for
> such a vast function. Also lua_cpcall causes much less diff.
> 
> We can do it, for example, by renaming luaL_tofield to luaL_tofield_xc
> and introducing new luaL_tofield, calling luaL_tofield_xc via
> lua_cpcall. Just like we used to work with C++ *_xc wrappers.
> 
> Please, ask again in the server team chat about the proposal above.
> Do not forget about stack overflow error, which also is possible and
> does not mean panic. Moreover, it is worth noting that diff is going
> to be much less and simpler. If they decline the proposal, I give in.
> 
> > -		luaL_tofield(L, cfg, idx, field);
> > -		return;
> > +		return luaL_tofield(L, cfg, idx, field);
> >   	} else if (!lua_isstring(L, -1)) {
> > -		luaL_error(L, "invalid " LUAL_SERIALIZE  " value");
> > +		diag_set(ClientError, ER_PROC_LUA,
> > +			 "invalid " LUAL_SERIALIZE " value");
> > +		return -1;
> >   	}
> >   	type = lua_tostring(L, -1);
> > @@ -525,94 +539,96 @@ luaL_tofield(struct lua_State *L, struct luaL_serializer *cfg, int index,
> >   			field->dval = num;
> >   			CHECK_NUMBER(num);
> >   		}
> > -		return;
> > +		break;
> 
> 4. Why no to return 0? Anyway all your breaks lead to a simple 'return 0'.
> 
> > @@ -620,14 +636,15 @@ luaL_tofield(struct lua_State *L, struct luaL_serializer *cfg, int index,
> >   		field->sval.len = 0;
> >   		if (lua_touserdata(L, index) == NULL) {
> >   			field->type = MP_NIL;
> > -			return;
> > +			break;
> >   		}
> >   		/* Fall through */
> >   	default:
> >   		field->type = MP_EXT;
> > -		return;
> > +		break;
> >   	}
> >   #undef CHECK_NUMBER
> > +	return 0;
> >   }
> >   void

-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov