Nikolas Klauser 2527b071ba

[libc++] P2641R4: Checking if a union alternative is active (std::is_within_lifetime) (#165243) ...

<https://wg21.link/P2641R4>

Implements the C++26 function in `<type_traits>` [meta.const.eval] (and
the corresponding feature test macro `__cpp_lib_is_within_lifetime`)

```c++
template<class T>
  consteval bool is_within_lifetime(const T*) noexcept;
```

This is done with the `__builtin_is_within_lifetime` builtin added to
Clang 20 by #91895 / 2a07509c8d3c8b5b2c88e4f73dde0071bf506870. This is
not (currently) available with GCC.

This implementation has provisions for LWG4138
<https://cplusplus.github.io/LWG/issue4138> where it is ill-formed to
instantiate `is_within_lifetime<T>` with a function type `T`.

Closes #105381

Co-authored-by: Mital Ashok <mital@mitalashok.co.uk>

2025-11-02 10:30:31 +01:00

..

c.limits

…

limits

Remove last few bits for Native Client support (#148983)

2025-07-18 11:26:36 -04:00

support.limits.general

[libc++] P2641R4: Checking if a union alternative is active (std::is_within_lifetime) (#165243)

2025-11-02 10:30:31 +01:00