Re: table.unpack question.

[Dirk Laurie <dirk.laurie@...>]

2013/5/25 Pierre-Yves Gérardy <pygy79@gmail.com>:

> Lua 5.2 lifts this limit for `table.unpack()`, but the maximum size
> varies according to the circumstance.

> In my test case, it works up to 999970 in the REPL, and 999977
> from a script.

> Is there a any guaranteed safe size?

LUAI_MAXSTACK (see `luaconf.h`) less what you are already using.
Which depends.

It would be easy to do in C. The critical information is hidden from the
API, you only have `checkstack`. But even with that you could extract
the information by a bargaining process as the `#` function does.

You: What's the largest safe stack size?
Lua: How much do you want?
You: 1000000.
Lua: Sorry, you can't.
You: 1000000-32.
Lua: That's OK.
You: And what about 1000000-16?
etc.

The Lua designers encourage you to customize it. In `luaconf.h`:

@@ LUAI_MAXSTACK limits the size of the Lua stack.
** CHANGE it if you need a different limit. This limit is arbitrary;
** its only purpose is to stop Lua to consume unlimited stack
** space (and to reserve some numbers for pseudo-indices).
*/

So if you have a shiny new machine with lots of main main memory and your
window manager and browser is not hogging it all, you can probably hoick
it up by a factor of 50. Of course, Lua will do the hogging then :-)