Re: [ANN] LuaJIT Roadmap 2012/2013
- From: Henk Boom <henk@xxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Tue, 12 Jun 2012 16:01:49 -0400
On 12 June 2012 09:53, Mike Pall <mike-1206@xxxxxxxxxx> wrote:
> Robert G. Jakabosky wrote:
>> On Monday 11, Mike Pall wrote:
>> > Adam Strzelecki wrote:
>> > > for i = 0, 1000 -- some tight loop
>> > > local value = model[i] * view
>> > > gl.UniformMatrix4fv(location, 1, gl.TRUE, value.gl)
>> > > end
>> >
>> > Well, no, because 'value' *does* escape. There's no way for the
>> > compiler to know that gl.UniformMatrix4fv() doesn't store the
>> > 'value' pointer somewhere else.
>>
>> If gl.UniformMatrix4fv() did store the value and the value wasn't also stored
>> somewhere on the Lua side, then there is already a bug since the GC would
>> free
>> the value which might still be in use by the C code.
>
> No, there's a guarantee that arguments to a C function call are
> not collected before the C call returns.
I think the idea is that if the value doesn't escape on the lua side,
then having it escape on the C side would be unsafe either way, so you
might as well assume it doesn't. Does this make sense?
henk
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