Message-ID: <8a9a6084-2e39-50f1-d043-fa8c5ebdbd66@ivt.baug.ethz.ch>
Date: 2017-06-06T20:14:03Z
From: Kirill Müller
Subject: Usage of PROTECT_WITH_INDEX in R-exts
In-Reply-To: <22838.25257.371534.516276@stat.math.ethz.ch>
On 06.06.2017 10:07, Martin Maechler wrote:
>>>>>> Kirill M?ller <kirill.mueller at ivt.baug.ethz.ch>
>>>>>> on Mon, 5 Jun 2017 17:30:20 +0200 writes:
> > Hi I've noted a minor inconsistency in the documentation:
> > Current R-exts reads
>
> > s = PROTECT_WITH_INDEX(eval(OS->R_fcall, OS->R_env), &ipx);
>
> > but I believe it has to be
>
> > PROTECT_WITH_INDEX(s = eval(OS->R_fcall, OS->R_env), &ipx);
>
> > because PROTECT_WITH_INDEX() returns void.
>
> Yes indeed, thank you Kirill!
>
> note that the same is true for its partner function|macro REPROTECT()
>
> However, as PROTECT() is used a gazillion times and
> PROTECT_WITH_INDEX() is used about 100 x less, and PROTECT()
> *does* return the SEXP,
> I do wonder why PROTECT_WITH_INDEX() and REPROTECT() could not
> behave the same as PROTECT()
> (a view at the source code seems to suggest a change to be trivial).
> I assume usual compiler optimization would not create less
> efficient code in case the idiom PROTECT_WITH_INDEX(s = ...)
> is used, i.e., in case the return value is not used ?
>
> Maybe this is mainly a matter of taste, but I find the use of
>
> SEXP s = PROTECT(........);
>
> quite nice in typical cases where this appears early in a function.
> Also for that reason -- but even more for consistency -- it
> would also be nice if PROTECT_WITH_INDEX() behaved the same.
Thanks, Martin, this sounds reasonable. I've put together a patch for
review [1], a diff for applying to SVN (via `cat | patch -p1`) would be
[2]. The code compiles on my system.
-Kirill
[1] https://github.com/krlmlr/r-source/pull/5/files
[2] https://patch-diff.githubusercontent.com/raw/krlmlr/r-source/pull/5.diff
>
> Martin
>
> > Best regards
> > Kirill