CWG2678 std::source_location::current is unimplementable

[jensmaurer]

CWG alerts LWG and LEWG of serious implementability concerns when std::source_location::current appears in a constant expression in an inline function or in a function template.

See CWG2678 for details.

[brycelelbach]

@JeffGarland we'll take a first crack at this.

[billy-baker]

2023-02-06 15:30 to 17:30 Issaquah Library Evolution Meeting

CWG2678: source_location::current is unimplementable

2023-02-06 15:30 to 17:30 UTC-8 Issaquah Library Evolution Minutes

Attendance: 28 (room) + 12 (zoom)

Champion: Richard Smith

Chair: Billy Baker and Steve Downey

Minute Taker: Robert Leahy

Start: 2023-02-06 16:00 Pacific

POLL: Accessors should not be usable in constant expressions if the usage (e.g. within inline function, partial specializations, ...) could result in more than one definition (Richard's suggestion).

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
3	13	5	3	1

Attendance: 28 (room) + 12

# of Authors: 2

Author Position: 2 x SF

Outcome: Consensus for not allowing access to members.

End: 16:50

Summary

LEWG agrees with the approach that Richard suggested in which the source_location member functions are not usable in a constant expression if the usage of current() could result in multiple definitions.