Re: [9fans] Go and 21-bit runes (and a bit of Go status)

[Bakul Shah <bakul@bitblocks.com>]

On Jun 3, 2013, at 10:07 AM, erik quanstrom <quanstro@quanstro.net> wrote:

> On Mon Jun  3 13:05:07 EDT 2013, lucio@proxima.alt.za wrote:
>>> if by intent, you mean that go is using xmm registers as if they were
>>> general purpose registers, then the solution is to stop doing that.
>>> and there's such a patch already.
>> 
>> No, Go's intent is to minimise runtime surprises.  It is possible to
>> define signal (calling them notes does not change their nature)
>> handlers and nothing in the Go specifications compels the user not to
>> use floating point instructions in such handlers.  It would also not
>> be possible to enforce such restrictions in known implementations of
> 
> signals are not compatable with notes.  i don't think this
> can be truely portable code anyway.

Not compatible but signals have similar restrictions. A signal may be delivered at any time where any state maintained in usercode may be inconsistent. In particular use of any non-reentrant function can cause trouble. Used to be, you don't use floating pt. in signal handlers as that would require the kernel to save more state, slowing down signal delivery, or it could cause another trap where the kernel can do the lazy saving trick. Most mallocs are non reentrant as well and you shouldn't use malloc in a handler. All in all a very restricted environment.