[PATCH] D103935: Add Twine support for std::string_view.

[David Blaikie via Phabricator via llvm-commits]

dblaikie added a comment.

Yeah, the current state of this is not acceptable - compatibility across different standard versions is necessary.

In D103935#2881775 <https://reviews.llvm.org/D103935#2881775>, @dexonsmith wrote:

> @dblaikie / @lhames , maybe one of you has ideas for how to add Twine support for std::string_view in C++17 and later without changing Twine's ABI?
>
> I think the following won't work, because the lifetime of the StringRef wouldn't be extended to match the lifetime of the calling expression:
>
>   Twine(const std::string_view &view) : Twine(StringRef(view)) {}

Yep.

Would it be so bad if we made "Child" larger by storing a StringRef (or equivalent - anything involving a pointer+length) in it (so Child would be two words rather than one)? Then we could collapse several cases into that (StringRef, string_view, std::string, SmallString, (could even do char as well)).


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https://reviews.llvm.org/D103935