[Tarantool-patches] [PATCH v2 05/15] lua: don't raise a Lua error from luaT_tuple_new()

[Alexander Turenko]

On Thu, Oct 15, 2020 at 01:41:45AM +0200, Vladislav Shpilevoy wrote:
> On 12.10.2020 12:37, Alexander Turenko wrote:
> >>> Disallow creating a tuple from objects on the Lua stack (idx == 0) in
> >>> luaT_tuple_new() for simplicity. There are no such usages in tarantool.
> >>> The function is not exposed yet to the module API. This is only
> >>> necessary in box.tuple.new(), which anyway raises Lua errors by its
> >>> contract.
> >>
> >> 1. But why? The case of creating a tuple from values may be much faster,
> >> when there is a lot of values not wrapped into a table. Table wrap is
> >> costly.
> >>
> >> Could you just merge luaT_tuple_encode_values and luaT_tuple_encode_table
> >> into one function, withuout splitting them?
> > 
> > I started with this variant, but then found that it'll require copying
> > of all arguments before pcall() (at least if we must leave them on the
> > stack after exiting from the function). Even if we'll decide to include
> > a remark like 'the function pops all values in case of idx == 0', we'll
> > need to put a function before the arguments and so we'll move all stack
> > values. Anyway it looks lopsided: in one case arguments are popped, but
> > in another they are kept on the stack.
> > 
> > I guess it would have a chance to be useful if it would allow to pass a
> > range of lua stack indices. But not sure.
> 
> I created an issue for that: https://github.com/tarantool/tarantool/issues/5406
> (At least it is related, and this place is not the only problematic one.)

Hmm. I don't see how it is related to the question.