[R] STRING_PTR_RO compared to STRING_ELT

[Tim Taylor]

Many thanks Iris

That's very helpful.

Tim

On Mon, 5 Oct 2026, at 5:01 PM, Iris Simmons wrote:
> STRING_PTR_RO(x)[i] will not check bounds and will not check that the 
> element is not NULL and not a free node. STRING_PTR_RO only works on 
> standard vectors, and will not work on alternate vector 
> representations. Also, it will return (const SEXP *) (void *) 1 when 
> the character vector is of length 0, or may return a pointer to a 
> random place in memory. In general, I would suggest
>
> const SEXP *y = NULL;
> if (Rf_xlength(x)) y = STRING_PTR_RO(x);
>
> or something similar in order to avoid anything weird involving 0 length access.
>
> I do not know of any other differences to note. 
>
> On Mon, Oct 5, 2026, 11:36 Tim Taylor <tim.taylor using hiddenelephants.co.uk> wrote:
>> Apart from different ergonomics is there anything worth being aware of when using STRING_PTR_RO versus STRING_ELT for getting CHARSXP?
>> 
>> Tim
>> 
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