romainfrancois commented on a change in pull request #8246:
URL: https://github.com/apache/arrow/pull/8246#discussion_r494154401
##########
File path: r/src/arrow_cpp11.h
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@@ -157,8 +157,15 @@ struct ns {
template <typename Pointer>
Pointer r6_to_pointer(SEXP self) {
- return reinterpret_cast<Pointer>(
- R_ExternalPtrAddr(Rf_findVarInFrame(self, arrow::r::symbols::xp)));
+ void* p = R_ExternalPtrAddr(Rf_findVarInFrame(self, arrow::r::symbols::xp));
+ if (p == nullptr) {
Review comment:
We can't really do that because of the implicit `else NULL` case:
```r
shared_ptr <- function(class, xp) {
if (!shared_ptr_is_null(xp)) class$new(xp)
}
```
There are cases where we want an R NULL when the internal C++ shared pointer
holds a C++ null pointer, e.g. when we call:
```c++
std::shared_ptr<Array> RecordBatch::GetColumnByName(const std::string& name)
const {
auto i = schema_->GetFieldIndex(name);
return i == -1 ? NULLPTR : column(i);
}
```
For example in this tests:
```r
test_that("[[ and $ on RecordBatch", {
[...]
expect_null(batch$qwerty)
[...]
})
```
having the extra layer with the R function `shared_ptr(T, .)` maybe calling
`T$new(.)` gives the NULL.
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