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[support.srcloc] It's underspecified whether copy/move functions of source_location are constexpr or not #3170

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frederick-vs-ja opened this issue Aug 12, 2019 · 4 comments · Fixed by #3309
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[support.srcloc] It's underspecified whether copy/move functions of source_location are constexpr or not #3170

frederick-vs-ja opened this issue Aug 12, 2019 · 4 comments · Fixed by #3309
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@jensmaurer

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@frederick-vs-ja
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Since the actual data members of std::source_location are not precisely specified, leaving these special member functions (copy/move constructor and copy/move assignment operator) implicitly declared might be insufficient to make them usable in constant evaluation.

I think it might be better to specify them as constexpr, either in the synopsis or in [source_location.syn]/3.
@frederick-vs-ja frederick-vs-ja changed the title [support.srcloc] It's underspecified whether copy/move functions of source_location are constexpr [support.srcloc] It's underspecified whether copy/move functions of source_location are constexpr or not Aug 12, 2019
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Or can we just specify that std::source_location is a trivially copyable type?
An implementation of std::experimental::source_location by gcc libstdc++ (which is the only implementation I can find) is already trivially copyable.

@jensmaurer jensmaurer added the lwg Issue must be reviewed by LWG. label Sep 5, 2019
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Sounds like a LWG issue to me.

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Submitted to lwgchair.

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jensmaurer commented Oct 12, 2019 •
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According to www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1208r6.pdf, it is intentionally unspecified (by absence) whether these functions are trivially copyable. We could assume the same applies to "constexpr". Let's add a note highlighting the "unspecified" fact.

@jensmaurer jensmaurer removed the lwg Issue must be reviewed by LWG. label Oct 12, 2019
@jensmaurer jensmaurer self-assigned this Oct 20, 2019
@jensmaurer jensmaurer mentioned this issue Oct 20, 2019
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[support.srcloc.class] Highlight unspecified properties jensmaurer/draft
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