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LWG4015 [optional.optional] Can we eliminate the exposition only member val? #4754

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frederick-vs-ja opened this issue Jul 16, 2021 · 4 comments
Open

LWG4015 [optional.optional] Can we eliminate the exposition only member val? #4754

frederick-vs-ja opened this issue Jul 16, 2021 · 4 comments

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@frederick-vs-ja
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frederick-vs-ja commented Jul 16, 2021 •
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As std::optional has been required to propagate copy/move triviality, a pointer data member that always points to the contained value cannot be a viable implementation strategy if any of copy/move triviality is propagated.
Can we eliminate val and just use "the contained value" (or its address) instead?
@jensmaurer
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This sounds plausible. After all, we can't really update an internal pointer during a trivial copy operation.

However, there are quite a few mentions of val in the text. @jwakely , what would be your preferred approach?

@jensmaurer
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@jwakely , ping.

@jwakely
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jwakely commented Sep 2, 2021

We could replace val->~T() with value().~T(), and talk about the state of value() instead of *val. And in the accessors that return val or *val we could talk about "the contained value". I think that could work, but it probably needs LWG review (or even an LWG issue).

@frederick-vs-ja
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LWG4015 seemingly addresses this.

@frederick-vs-ja frederick-vs-ja changed the title [optional.optional] Can we eliminate the exposition only member val? LWG4015 [optional.optional] Can we eliminate the exposition only member val? Nov 25, 2023
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@jwakely @frederick-vs-ja @jensmaurer