Re: lua_checkstack necessity
- From: Tyson Nottingham <tgnottingham@xxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Thu, 23 Oct 2014 12:11:50 -0700
Thanks. I'm wondering specifically about LuaJIT -- does it make any
additional guarantees about the stack size, beyond Lua's LUA_MINSTACK
guarantee you mentioned? The LuaJIT source suggests that
lua_checkstack calls are unnecessary in many/most cases according to
my understanding. I'm just wondering if this is something that I can
rely on when using LuaJIT going forward. I.e. is this something that
LuaJIT guarantees or is highly unlikely to change in the
implementation in the near future?
On Thu, Oct 23, 2014 at 11:29 AM, Daurnimator <quae@xxxxxxxxxxxxxxx> wrote:
> On 23 October 2014 14:23, Tyson Nottingham <tgnottingham@xxxxxxxxx> wrote:
>>
>> I've noticed that many LuaJIT C API functions manage the stack size
>> without requiring me to use lua_checkstack(). E.g. I can call
>> lua_pushnumber() up to around LUAI_MAXSTACK times in a loop without
>> any apparent memory issues. In the source, I can see that many
>> functions call incr_top(), which grows the stack according to my
>> understanding.
>>
>> Does this make calling lua_checkstack() unnecessary before calling the
>> basic functions that push elements onto the stack (lua_pushxxx(),
>> lua_next(), etc.) when using the LuaJIT implementation? Are there any
>> exceptions? Is this implicit stack management something that I can
>> rely on, or should I consider it an implementation detail that may
>> change? Also, is this documented anywhere?
>>
>> Thanks,
>> Tyson
>>
>
> From http://www.lua.org/manual/5.2/manual.html#4.2:
>
> Whenever Lua calls C, it ensures that the stack has at least LUA_MINSTACK
> extra slots.
> LUA_MINSTACK is defined as 20, so that usually you do not have to worry
> about stack space
> unless your code has loops pushing elements onto the stack.
>
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