Landing: 4442e8b6cbff
Project / Subsystem
gcc / libstdc++,testsuite
Date
2026-09-14
Author
Jakub Jelinek
Commit
4442e8b6cbffd113ec7bd25f449cc18f104f7150
Source
github
Perf win
No
Breaking
No
All attributes
- project
- gcc
- subsystem
- libstdc++,testsuite
- patch_id
- —
- commit_hash
- 4442e8b6cbffd113ec7bd25f449cc18f104f7150
- source_type
- github
- headline
- Implement C++26 std::is_within_lifetime extension.
- tldr
- C++26 `std::is_within_lifetime` is now implemented in libstdc++ using compiler built-ins.
- author
- Jakub Jelinek
- outcome
- committed
- performance_win
- false
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • libstdc++
- • c++26
- • compiler
- • type traits
- • UB
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-09-14T00:00:00.000Z
GCC’s libstdc++ now implements the C++26 proposal P3450R1, which extends std::is_within_lifetime. This implementation uses __builtin_constant_p to determine if a static_cast mandated by the standard can be evaluated as a constant expression. New test cases verify this functionality.