NL375 D.19 [depr.fs.path.factory] Clarify that std::string is not good for UTF-8 LWG 3328

[wg21bot]

Example in deprecated section implies that std::string is the type to use for utf8 strings.
[Example: A string is to be read from a database that is encoded in UTF-8, and used to create a
directory using the native encoding for filenames:
namespace fs = std::filesystem;
std::string utf8_string = read_utf8_data();
fs::create_directory(fs::u8path(utf8_string));

Proposed change:
Add clarification that std::string is the wrong type for utf8 strings

[tahonermann]

SG16 plans to discuss this comment Tuesday morning:

• http://wiki.edg.com/bin/view/Wg21belfast/SG16

[tahonermann]

SG16 in Belfast: Recommend to accept with a modification to update the example in [depr.fs.path.factory]p4 to state that std::u8string should be preferred for UTF-8 data.

Rationale: The example code is representative of historic use of std::filesystem::u8path and should not be changed to use std::u8string. The recommended change is to a non-normative example and may therefore be considered editorial.

Removing the SG16 label. This now goes to LWG.

Minutes are available at:

• http://wiki.edg.com/bin/view/Wg21belfast/SG16NBNL375

[JeffGarland]

New LWG issue submitted to update wording.

[Dani-Hub]

The associated issue is LWG 3328

[JeffGarland]

Full group in Prague Monday afternoon. Consensus to prioritize issue as P0.

[mclow]

Accepted. LWG3328 will be moved on Saturday in Prague.