Fmt: Implementation of basic_string_view clashes with std

[Kronuz]

I had to remove the implementation of std::basic_string_view for pre-C++17 since it didn't allow me to pass string_view object to fmt, it said (it didn't know how to convert from basic_string_view to basic_string_view). After that, it worked.

[vitaut]

There is an implicit conversion from std::basic_string_view to fmt::basic_string_view: https://github.com/fmtlib/fmt/blob/84e520b79c9c894c6e71a979660fc1278e032dd4/include/fmt/core.h#L240 so the following should work:

fmt::format(std::string_view("{}"), 42);

provided that string_view is detected on your platform. Which compiler version do you use?

[Kronuz]

I’m using clang 5 in macOS it didn’t work until I removed the custom basic_string_view; and apparently it did detect it.

[vitaut]

Hmm, according to godbolt std::string_view is detected and works: https://godbolt.org/g/3n2XBe

Could you post a reproducible example and the full error message?

[Kronuz]

Done! Probably detection isn’t lacking, since std::string_view is available since c++14 in clang 4 and 5. Simply change to -std=c++14 so you see it fail (note it does have std::string_view available anyway)

[vitaut]

C++14 doesn't have std::string_view, so the error is expected. You can use std::experimental::string_view with C++14: https://godbolt.org/g/eFMRTQ

[Kronuz]

...well, I’m successfully using std::string_view all over the place in clang 4 and 5 c++14, so I guess we could support it too, couldn’t we?

[vitaut]

What compiler flags do you use? std::string_view is not supported with -std=c++14: https://godbolt.org/g/LLKw3P

[mwinterb]

libc++ supports it in C++14, and apparently back to C++03, see
https://github.com/abseil/abseil-cpp/issues/2

On Wed, Mar 21, 2018, 18:32 Victor Zverovich [e-mail]
wrote:

What compiler flags do you use? std::string_view is not supported with
-std=c++14: https://godbolt.org/g/LLKw3P

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[Kronuz]

https://wandbox.org/permlink/5wvB24tzaF3ggxgb

[vitaut]

Fixed, thanks for reporting!