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by levzettelin 282 days ago

  // You are responsible for releasing the structure in the end
  arrow_array.release(&arrow_array);
This doesn't look like RAII. How is this idiomatic for C++20? Why do you have to pass a pointer to "this" again as an explicit argument.
2 comments

This is the extracted Arrow C data interfaces as documented in https://arrow.apache.org/docs/format/CDataInterface.html

It's not how you interact with the data in your own C++ code, it's for passing this data to other in-process consumers (libraries etc). While in the example it calls the release function, this is usually just passed to a downstream consumer and it's their responsibility to call it.

I agree that having such an example as the first one is confusing. Given that a large part of the point of Apache Arrow is passing data columnar data between libraries in different languages in memory, it makes some sense.

It's not how you interact with the data in your own C++ code, it's for passing this data to other in-process consumers (libraries etc). While in the example it calls the release function, this is usually just passed to a downstream consumer and it's their responsibility to call it.

This seems like a strange rationalizations when you don't need to have explicit release to be able to pass it to something else.

RAII predates C++98, I was already used to it in Turbo C++ for MS-DOS, and is pity we need to keep advocating for it as something extraordinary.
I think you're partly making the point for them, RAII has been idiomatic C++ since before c++ was standardized. It wasn't even idiomatic c++98 to be missing it, so to be missing it in c++20 library definitely still isn't.
Indeed, that is the point.
This doesn't have anything to do with what they said, they didn't say RAII was new.
Might be misunderstood by others not skilled in C++ when reading,

> This doesn't look like RAII. How is this idiomatic for C++20?

You can try to be insulting if you want but if you could explain the connection I think you would have already.
I wasn't.
You weren't what? Who are you saying "isn't skilled in C++" here and why would that matter?