[Rd] strange increase in the reference number

[Gabriel Becker]

Hi Jiefei and Duncan,

I suspect what is likely happening is that one of  ENSURE_NAMEDMAX or
MARK_NOT_MUTABLE are being hit for x. These used to set named to 3, but now
set it to 7 (ie the previous and current NAMEDMAX  value, respectively).

Because these are macros rather than C functions, its not easy to figure
out why one of them is being invoked from do_isvector  (a cursory
exploration didn't reveal what was going on, at least to me) and I don't
have the time to dig super deeply into this right now,  but perhaps Luke or
Tomas know why this is happening of the top of their head.

Sorry I can't be of more help.

~G



On Fri, Jul 12, 2019 at 11:47 AM Duncan Murdoch <murdoch.duncan using gmail.com>
wrote:

> On 12/07/2019 1:22 p.m., King Jiefei wrote:
> > Hi,
> >
> > I just found a strange increase in the reference number and I'm wondering
> > if there is any reason for it, here is the code.
> >
> >> a=c(1,2,3)
> >> .Internal(inspect(a))
> > @0x000000001bf0b9b0 14 REALSXP g0c3 [NAM(1)] (len=3, tl=0) 1,2,3
> >> is.vector(a)
> > [1] TRUE
> >> .Internal(inspect(a))
> > @0x000000001bf0b9b0 14 REALSXP g0c3 [NAM(7)] (len=3, tl=0) 1,2,3
> >
> > The variable *a* initially has one reference number, after calling
> > *is.vector* function, the reference number goes to 7, which I believe is
> > the highest number that is allowed in R.  I also tried the other R
> > functions, *is.atomic, is.integer* and *is.numeric* do not increase the
> > reference number, but *typeof *will do. Is it intentional?
>
> is.vector() is a closure that calls .Internal.  is.atomic(),
> is.integer() and is.numeric() are all primitives.
>
> Generally speaking closures that call .Internal are easier to implement
> (e.g. is.vector can use the regular mechanism to set a default for its
> second argument), but less efficient in CPU time.  From it's help page,
> it appears that the logic for is.vector() is a lot more complex than for
> the others, so that implementation does make sense.
>
> So why does NAMED go to 7?  Initially, the vector is bound to a.  Within
> is.vector, it is bound to the local variable x.  At this point there are
> two names bound to the same object, so it has to be considered
> immutable.  There's really no difference between any of the values of 2
> or more in the memory manager.  (But see
> http://developer.r-project.org/Refcnt.html for some plans.  That
> document is from about 5 years ago; I don't know the current state.)
>
> Duncan Murdoch
>
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