From 0d66b5a135f3e56041e0252e1f6d7cf8f598c8c2 Mon Sep 17 00:00:00 2001
From: ADAM David Alan Martin <adam@recursive.engineer>
Date: Fri, 10 Nov 2023 23:15:37 -0500
Subject: [PATCH] This should be in C++23, but some compilers/libraries still
 lack it.

---
 lifetime.h | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 lifetime.h

diff --git a/lifetime.h b/lifetime.h
new file mode 100644
index 0000000..aa44f0e
--- /dev/null
+++ b/lifetime.h
@@ -0,0 +1,39 @@
+static_assert( __cplusplus > 2020'00 );
+
+#pragma once
+
+#include <Alepha/Alepha.h>
+
+#include <cstddef>
+
+#include <type_traits>
+
+namespace Alepha::Hydrogen  ::detail:: lifetime_m
+{
+	inline namespace exports
+	{
+		// When C++23 arrives, just turn these into `using` statements.
+
+		template< typename T >
+		std::add_pointer_t< T >
+		start_lifetime_as( void *const mp ) noexcept
+		{
+			const auto raw= new( mp ) std::byte[ sizeof( T ) ];
+			const auto data= reinterpret_cast< std::add_pointer_t< T > >( raw );
+			return std::launder( data );
+		}
+
+		template< typename T >
+		std::add_pointer_t< std::add_const_t< T > >
+		start_lifetime_as( const void *const p ) noexcept
+		{
+			const auto mp= const_cast< void * >( p );
+			return start_lifetime_as< std::add_const_t< T > >( mp );
+		}
+	}
+}
+
+namespace Alepha::Hydrogen::inline exports::inline lifetime_m
+{
+	using namespace detail::lifetime_m::exports;
+}