feature/spaceship: Clause 32: Thread support (#1590)

Co-authored-by: Stephan T. Lavavej <[email protected]>

Author: statementreply

stl/inc/thread

@@ -14,6 +14,7 @@
 #include <tuple>
 #include <xthreads.h>
 #if _HAS_CXX20
+#include <compare>
 #include <stop_token>
 #endif // _HAS_CXX20
 
@@ -215,7 +216,11 @@ private:
     friend thread::id thread::get_id() const noexcept;
     friend thread::id this_thread::get_id() noexcept;
     friend bool operator==(thread::id _Left, thread::id _Right) noexcept;
+#if _HAS_CXX20
+    friend strong_ordering operator<=>(thread::id _Left, thread::id _Right) noexcept;
+#else // ^^^ _HAS_CXX20 / !_HAS_CXX20 vvv
     friend bool operator<(thread::id _Left, thread::id _Right) noexcept;
+#endif // !_HAS_CXX20
     template <class _Ch, class _Tr>
     friend basic_ostream<_Ch, _Tr>& operator<<(basic_ostream<_Ch, _Tr>& _Str, thread::id _Id);
     friend hash<thread::id>;
@@ -237,6 +242,11 @@ _NODISCARD inline bool operator==(thread::id _Left, thread::id _Right) noexcept
     return _Left._Id == _Right._Id;
 }
 
+#if _HAS_CXX20
+_NODISCARD inline strong_ordering operator<=>(thread::id _Left, thread::id _Right) noexcept {
+    return _Left._Id <=> _Right._Id;
+}
+#else // ^^^ _HAS_CXX20 / !_HAS_CXX20 vvv
 _NODISCARD inline bool operator!=(thread::id _Left, thread::id _Right) noexcept {
     return !(_Left == _Right);
 }
@@ -256,6 +266,7 @@ _NODISCARD inline bool operator>(thread::id _Left, thread::id _Right) noexcept {
 _NODISCARD inline bool operator>=(thread::id _Left, thread::id _Right) noexcept {
     return !(_Left < _Right);
 }
+#endif // !_HAS_CXX20
 
 template <class _Ch, class _Tr>
 basic_ostream<_Ch, _Tr>& operator<<(basic_ostream<_Ch, _Tr>& _Str, thread::id _Id) {

tests/std/tests/P1614R2_spaceship/test.cpp

@@ -21,6 +21,7 @@
 #include <stack>
 #include <string>
 #include <system_error>
+#include <thread>
 #include <type_traits>
 #include <unordered_map>
 #include <unordered_set>
@@ -481,6 +482,14 @@ void ordering_test_cases() {
 
         spaceship_test<std::strong_ordering>(c_mem[0], c_mem[0], c_mem[1]);
     }
+    { // thread::id
+        std::thread::id id1;
+        std::thread::id id1_equal;
+        std::thread::id id2 = std::this_thread::get_id();
+
+        // Implementation-specific assumption: std::thread::id{} occurs first in the unspecified total ordering.
+        spaceship_test<std::strong_ordering>(id1, id1_equal, id2);
+    }
 }
 
 template <class Element, class Ordering>