jgehrcke commented on code in PR #15049:
URL: https://github.com/apache/arrow/pull/15049#discussion_r1056225766
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cpp/src/arrow/dataset/file_base.h:
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@@ -200,6 +200,9 @@ class ARROW_DS_EXPORT FileFormat : public
std::enable_shared_from_this<FileForma
fs::FileLocator destination_locator) const = 0;
/// \brief Get default write options for this format.
+ ///
+ /// May return nullptr if this file format does not yet support writing
Review Comment:
Ha. OK.
I will revert the code change.
About the comment, however: I am not convinced that "empty shared_ptr" is
correct. "empty shared_ptr" means primarily that the pointer owns nothing.
Whether or not this is a shared_ptr that points to nothing (i.e., whose get()
== nullptr) is not defined by the word "empty".
It's seemingly not as simple as "It seems that a std::shared_ptr that stores
nullptr is called empty".
This following paragraph makes it rather clear to me (emphasis mine):
> A shared_ptr that does not own any pointer is called an empty shared_ptr.
**A shared_ptr that points to no object is called a null shared_ptr** and shall
not be [dereferenced](https://cplusplus.com/shared_ptr::operator*). Notice
though that **an empty shared_ptr is not necessarily a null shared_ptr, and a
null shared_ptr is not necessarily an empty shared_ptr**.
(https://cplusplus.com/reference/memory/shared_ptr/)
Given these statements the term "null shared_ptr" seems to be more
appropriate than "empty shared_ptr".
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