[libc-commits] [libc] [libc] implement `memalignment` (PR #132493)

[Michael Jones via libc-commits]

================
@@ -0,0 +1,59 @@
+//===-- Unittests for memalignment ----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdlib/memalignment.h"
+#include "test/UnitTest/Test.h"
+
+#include <stdint.h>
+
+TEST(LlvmLibcMemAlignmentTest, NullPointer) {
+  void *ptr = nullptr;
+  EXPECT_EQ(LIBC_NAMESPACE::memalignment(ptr), static_cast<size_t>(0));
+}
+
+TEST(LlvmLibcMemAlignmentTest, SpecificAlignment) {
+
+  // These addresses have known alignment patterns - if we can construct them
+  uintptr_t addr_align2 = 0x2;   // 2-byte aligned
+  uintptr_t addr_align4 = 0x4;   // 4-byte aligned
+  uintptr_t addr_align8 = 0x8;   // 8-byte aligned
+  uintptr_t addr_align16 = 0x10; // 16-byte aligned
+  uintptr_t addr_align32 = 0x20; // 32-byte aligned
+
+  void *ptr_align2 = reinterpret_cast<void *>(addr_align2);
+  void *ptr_align4 = reinterpret_cast<void *>(addr_align4);
+  void *ptr_align8 = reinterpret_cast<void *>(addr_align8);
+  void *ptr_align16 = reinterpret_cast<void *>(addr_align16);
+  void *ptr_align32 = reinterpret_cast<void *>(addr_align32);
+
+  EXPECT_EQ(LIBC_NAMESPACE::memalignment(ptr_align2), static_cast<size_t>(2));
+  EXPECT_EQ(LIBC_NAMESPACE::memalignment(ptr_align4), static_cast<size_t>(4));
+  EXPECT_EQ(LIBC_NAMESPACE::memalignment(ptr_align8), static_cast<size_t>(8));
+  EXPECT_EQ(LIBC_NAMESPACE::memalignment(ptr_align16), static_cast<size_t>(16));
+  EXPECT_EQ(LIBC_NAMESPACE::memalignment(ptr_align32), static_cast<size_t>(32));
+
+  uintptr_t addr_complex = 0x1234560; // 16-byte aligned (ends in 0)
+  void *ptr_complex = reinterpret_cast<void *>(addr_complex);
+  EXPECT_EQ(LIBC_NAMESPACE::memalignment(ptr_complex), static_cast<size_t>(16));
----------------
michaelrj-google wrote:

This test is currently failing because `0x60` has 5 trailing zeroes (`0b1100000`) so it's 32 byte aligned. Either change the comment and the result or change the address.

https://github.com/llvm/llvm-project/pull/132493