mame @0.203: error: no member named 'experimental' in namespace 'std'

[Tatsh (Andrew Udvare)]

It fails when building anything using the included asio library under 3rdparty.

:info:build ../../../../../3rdparty/asio/include/asio/ip/impl/address.ipp:139:22: error: unknown type name 'string_view'; did you mean 'std::string_view'?
:info:build address make_address(string_view str)
:info:build                      ^~~~~~~~~~~
:info:build                      std::string_view
:info:build In file included from ../../../../../src/emu/http.cpp:1:
:info:build In file included from ../../../../../src/emu/emu.h:29:

I'm on Catalina with Xcode 11 which may be causing this.

[Tatsh (Andrew Udvare)]

build log

[ryandesign (Ryan Carsten Schmidt)]

Looks like the first error in the log is actually:

:info:build ../../../../../3rdparty/asio/include/asio/detail/string_view.hpp:31:12: error: no member named 'experimental' in namespace 'std'
:info:build using std::experimental::basic_string_view;
:info:build       ~~~~~^
:info:build ../../../../../3rdparty/asio/include/asio/detail/string_view.hpp:32:12: error: no member named 'experimental' in namespace 'std'
:info:build using std::experimental::string_view;
:info:build       ~~~~~^

In any case, this sounds like a problem that is not specific to MacPorts. I will update the port to the latest version, 0.216. If the problem persists with that version, please ​report the problem to the developers; they may need to update their bundled asio library.