Note that your desire is by definition impossible - as your example also shows
checking for S4 inheritance involves evaluation and thus allocation which
cannot be avoided by the dynamic design of S4 inheritance.
Cheers,
Simon
> On Nov 1, 2019, at 9:23 AM, Jan Gorecki <j.gore...@wit.edu.pl> wrote:
>
> Thank you Luke.
> That is why I don't use Rf_inherits but INHERITS which does not
> allocate, provided in the email body.
> I cannot do similarly for S4 classes, thus asking for some API for that.
>
> On Fri, Nov 1, 2019 at 5:56 PM Tierney, Luke <luke-tier...@uiowa.edu> wrote:
>>
>> On Fri, 1 Nov 2019, Jan Gorecki wrote:
>>
>>> Dear R developers,
>>>
>>> Motivated by discussion about checking inheritance of S3 and S4
>>> objects (in head matrix/array topic) I would light to shed some light
>>> on a minor gap about that matter in R C API.
>>> Currently we are able to check inheritance for S3 class objects from C
>>> in a robust way (no allocation, thread safe). This is unfortunately
>>
>> Your premise is not correct. Rf_inherits will not GC but it can
>> allocate and is not thread safe.
>>
>> Best,
>>
>> luke
>>
>>> not possible for S4 classes. I would kindly request new function in R
>>> C api so it can be achieved for S4 classes with no risk of allocation.
>>> For reference mentioned functions below. Thank you.
>>> Jan Gorecki
>>>
>>> // S3 inheritance
>>> bool INHERITS(SEXP x, SEXP char_) {
>>> SEXP klass;
>>> if (isString(klass = getAttrib(x, R_ClassSymbol))) {
>>> for (int i=0; i<LENGTH(klass); i++) {
>>> if (STRING_ELT(klass, i) == char_) return true;
>>> }
>>> }
>>> return false;
>>> }
>>> // S4 inheritance
>>> bool Rinherits(SEXP x, SEXP char_) {
>>> SEXP vec = PROTECT(ScalarString(char_));
>>> SEXP call = PROTECT(lang3(sym_inherits, x, vec));
>>> bool ans = LOGICAL(eval(call, R_GlobalEnv))[0]==1;
>>> UNPROTECT(2);
>>> return ans;
>>> }
>>>
>>> ______________________________________________
>>> R-devel@r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>
>>
>> --
>> Luke Tierney
>> Ralph E. Wareham Professor of Mathematical Sciences
>> University of Iowa Phone: 319-335-3386
>> Department of Statistics and Fax: 319-335-3017
>> Actuarial Science
>> 241 Schaeffer Hall email: luke-tier...@uiowa.edu
>> Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
>
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