--- /dev/null
+++ xnu/xnu-12377.121.6/tests/bounded_ptr_src/arith.difference.cpp
@@ -0,0 +1,122 @@
+//
+// Tests for
+//  friend std::ptrdiff_t operator-(bounded_ptr const& a, bounded_ptr const& b);
+//  friend std::ptrdiff_t operator-(bounded_ptr const& a, T* b);
+//  friend std::ptrdiff_t operator-(T* a, bounded_ptr const& b);
+//
+
+#include <libkern/c++/bounded_ptr.h>
+#include <array>
+#include <darwintest.h>
+#include <darwintest_utils.h>
+#include "test_utils.h"
+
+#define _assert(...) T_ASSERT_TRUE((__VA_ARGS__), # __VA_ARGS__)
+
+struct T {
+	int i;
+};
+
+template <typename Stored, typename Left, typename Right>
+static void
+tests()
+{
+	std::array<Stored, 5> array = {Stored{0}, Stored{1}, Stored{2}, Stored{3}, Stored{4}};
+
+	// a >= b
+	{
+		test_bounded_ptr<Left> const a(array.begin(), array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin(), array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == 0);
+	}
+	{
+		test_bounded_ptr<Left> const a(array.begin() + 1, array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin(), array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == 1);
+	}
+	{
+		test_bounded_ptr<Left> const a(array.begin() + 2, array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin(), array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == 2);
+	}
+	{
+		test_bounded_ptr<Left> const a(array.begin() + 3, array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin(), array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == 3);
+	}
+	{
+		test_bounded_ptr<Left> const a(array.begin() + 4, array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin(), array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == 4);
+	}
+	{
+		test_bounded_ptr<Left> const a(array.end(), array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin(), array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == 5);
+	}
+
+	// a < b
+	{
+		test_bounded_ptr<Left> const a(array.begin(), array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin() + 1, array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == -1);
+	}
+	{
+		test_bounded_ptr<Left> const a(array.begin(), array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin() + 2, array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == -2);
+	}
+	{
+		test_bounded_ptr<Left> const a(array.begin(), array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin() + 3, array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == -3);
+	}
+	{
+		test_bounded_ptr<Left> const a(array.begin(), array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin() + 4, array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == -4);
+	}
+	{
+		test_bounded_ptr<Left> const a(array.begin(), array.begin(), array.end());
+		test_bounded_ptr<Right> const b(array.begin() + 5, array.begin(), array.end());
+		std::ptrdiff_t diff = a - b;
+		_assert(diff == -5);
+	}
+
+	// Subtract pointers with different bounds
+	{
+		test_bounded_ptr<Left> const a(array.begin() + 2, array.begin() + 1, array.end() - 1);
+		test_bounded_ptr<Right> const b(array.begin() + 4, array.begin() + 3, array.end());
+		_assert(a - b == -2);
+		_assert(b - a == 2);
+	}
+
+	// Subtract with raw pointers
+	{
+		test_bounded_ptr<Left> const a(array.begin() + 2, array.begin() + 1, array.end() - 1);
+		Right* b = array.begin() + 4;
+		_assert(a - b == -2);
+	}
+	{
+		Left* a = array.begin() + 4;
+		test_bounded_ptr<Right> const b(array.begin() + 2, array.begin() + 1, array.end() - 1);
+		_assert(a - b == 2);
+	}
+}
+
+T_DECL(arith_difference, "bounded_ptr.arith.difference", T_META_TAG_VM_PREFERRED) {
+	tests<T, T, T>();
+	tests<T, T, T const>();
+	tests<T, T const, T>();
+	tests<T, T const, T const>();
+}