[Rd] Usage of PROTECT_WITH_INDEX in R-exts
maechler at stat.math.ethz.ch
Tue Jun 6 10:07:05 CEST 2017
>>>>> Kirill Müller <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.
> Best regards
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