[libcxx-commits] [libcxx] [libc++] Add a test case for std::bit_cast with std::complex (PR #97751)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne created https://github.com/llvm/llvm-project/pull/97751

This is extracted from #94620. While libc++ doesn't have the problem described in that issue, a test case is a good idea to ensure that we don't regress this behavior in the future. This could happen for example if we decide to use `_Complex` in the implementation of `std::complex` while Clang doesn't handle bit_cast with _Complex yet.

>From bf4ff86b0bf33b95bacce86a8039f56379034f15 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Thu, 4 Jul 2024 12:04:14 -0400
Subject: [PATCH] [libc++] Add a test case for std::bit_cast with std::complex

This is extracted from #94620. While libc++ doesn't have the problem
described in that issue, a test case is a good idea to ensure that
we don't regress this behavior in the future. This could happen for
example if we decide to use `_Complex` in the implementation of
`std::complex` while Clang doesn't handle bit_cast with _Complex yet.
---
 .../complex.number/complex/bit_cast.pass.cpp  | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 libcxx/test/std/numerics/complex.number/complex/bit_cast.pass.cpp

diff --git a/libcxx/test/std/numerics/complex.number/complex/bit_cast.pass.cpp b/libcxx/test/std/numerics/complex.number/complex/bit_cast.pass.cpp
new file mode 100644
index 0000000000000..7f15b6f9ade64
--- /dev/null
+++ b/libcxx/test/std/numerics/complex.number/complex/bit_cast.pass.cpp
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// Make sure that std::bit_cast works with std::complex. Test case extracted from
+// https://github.com/llvm/llvm-project/issues/94620.
+
+#include <bit>
+#include <complex>
+
+template <class T>
+constexpr void test() {
+  using Complex                       = std::complex<T>;
+  unsigned char data[sizeof(Complex)] = {0};
+
+  Complex c = std::bit_cast<Complex>(data);
+  (void)c;
+}
+
+constexpr bool test_all() {
+  test<float>();
+  test<double>();
+  test<long double>();
+  return true;
+}
+
+int main(int, char**) {
+  test_all();
+  static_assert(test_all());
+  return 0;
+}