P2590R2 Explicit Lifetime Management #2942

#define __cpp_lib_start_lifetime_as 202207L

template<typename _T>
_T* __builtin_start_lifetime_as(void*) noexcept;

template<typename _T>
const _T* __builtin_start_lifetime_as(const void*) noexcept;

template<typename _T>
volatile _T* __builtin_start_lifetime_as(volatile void*) noexcept;

template<typename _T>
const volatile _T* __builtin_start_lifetime_as(const volatile void*) noexcept;

template<typename _T>
_T* __builtin_start_lifetime_as_array(void*, size_t) noexcept;

template<typename _T>
const _T* __builtin_start_lifetime_as_array(const void*, size_t) noexcept;

template<typename _T>
volatile _T* __builtin_start_lifetime_as_array(volatile void*, size_t) noexcept;

template<typename _T>
const volatile _T* __builtin_start_lifetime_as_array(const volatile void*, size_t) noexcept;