string_ref not constructible from rvalue strings anymore

[Mathias Gaunard]

The change introduced in this commit is a regression ​https://github.com/boostorg/utility/commit/9960d9f395b79ee860e39064cd46961f76d2cb55

This breaks user code and is inconsistent with std::string_view. It is therefore undesirable.

[Marshall Clow]

Can you please give an (non-contrived) example of user code that is broken by this?

[arvid.norberg@…]

one example of this from my project:

std::string combine_path(string_view left, string_view right);

It used to be possible to nest these, like this:

auto a = combine_path(foo, combine_path(bar, b));

in boost-1.64 this is no longer possible, a proposed work-around is to introduce a string_view make_sv(std::string const&) function, to turn the temporary into an lvalue and construct the string_view from that. ​https://github.com/arvidn/libtorrent/pull/1814

[Marshall Clow]

thanks for the example. The change was made in response to ​https://svn.boost.org/trac/boost/ticket/11740. "string_ref not working correctly with rvalue of std::string"

[olafvdspek@…]

​https://github.com/mclow/String-Algo/issues/8

return db.query(make_query(db, q, a...));

make_query returns string, db.query takes string_view.