[libcxx-commits] [libcxxabi] [libcxx] [libc++] Fix noexcept behaviour of operator new helper functions (PR #74337)

[via libcxx-commits]

https://github.com/azhan92 created https://github.com/llvm/llvm-project/pull/74337

This PR removes the `noexcept` specification introduced in [`69407` ](https://github.com/llvm/llvm-project/pull/69407) since the standard allows

> throw an exception of type bad_alloc or a class derived from bad_alloc

as a behaviour of a `new_handler` function. The PR also adds a test to catch this. 

>From 5041d441856cda19cf796e16a13b4e0049d33342 Mon Sep 17 00:00:00 2001
From: Alison Zhang <alisonzhang at ibm.com>
Date: Mon, 4 Dec 2023 11:35:20 -0500
Subject: [PATCH] remove noexcept

---
 libcxx/src/new.cpp                        |  4 +--
 libcxxabi/src/stdlib_new_delete.cpp       |  4 +--
 libcxxabi/test/test_memory_alloc.pass.cpp | 34 +++++++++++++++++++++++
 3 files changed, 38 insertions(+), 4 deletions(-)
 create mode 100644 libcxxabi/test/test_memory_alloc.pass.cpp

diff --git a/libcxx/src/new.cpp b/libcxx/src/new.cpp
index 033bba5c1fc95..cb8b4aae8d5f9 100644
--- a/libcxx/src/new.cpp
+++ b/libcxx/src/new.cpp
@@ -20,7 +20,7 @@
 // in this shared library, so that they can be overridden by programs
 // that define non-weak copies of the functions.
 
-static void* operator_new_impl(std::size_t size) noexcept {
+static void* operator_new_impl(std::size_t size) {
   if (size == 0)
     size = 1;
   void* p;
@@ -87,7 +87,7 @@ _LIBCPP_WEAK void operator delete[](void* ptr, size_t) noexcept { ::operator del
 
 #  if !defined(_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION)
 
-static void* operator_new_aligned_impl(std::size_t size, std::align_val_t alignment) noexcept {
+static void* operator_new_aligned_impl(std::size_t size, std::align_val_t alignment) {
   if (size == 0)
     size = 1;
   if (static_cast<size_t>(alignment) < sizeof(void*))
diff --git a/libcxxabi/src/stdlib_new_delete.cpp b/libcxxabi/src/stdlib_new_delete.cpp
index 6c9990f063dde..f8a00ec584256 100644
--- a/libcxxabi/src/stdlib_new_delete.cpp
+++ b/libcxxabi/src/stdlib_new_delete.cpp
@@ -30,7 +30,7 @@
 // in this shared library, so that they can be overridden by programs
 // that define non-weak copies of the functions.
 
-static void* operator_new_impl(std::size_t size) noexcept {
+static void* operator_new_impl(std::size_t size) {
   if (size == 0)
     size = 1;
   void* p;
@@ -107,7 +107,7 @@ void operator delete[](void* ptr, size_t) noexcept { ::operator delete[](ptr); }
 
 #if !defined(_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION)
 
-static void* operator_new_aligned_impl(std::size_t size, std::align_val_t alignment) noexcept {
+static void* operator_new_aligned_impl(std::size_t size, std::align_val_t alignment) {
   if (size == 0)
     size = 1;
   if (static_cast<size_t>(alignment) < sizeof(void*))
diff --git a/libcxxabi/test/test_memory_alloc.pass.cpp b/libcxxabi/test/test_memory_alloc.pass.cpp
new file mode 100644
index 0000000000000..219b85b9afcaf
--- /dev/null
+++ b/libcxxabi/test/test_memory_alloc.pass.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// 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: no-exceptions
+
+#include <new>
+#include <cassert>
+#include <limits>
+
+int new_handler_called = 0;
+
+void my_new_handler() {
+  ++new_handler_called;
+  throw std::bad_alloc();
+}
+
+int main(int, char**) {
+  std::set_new_handler(my_new_handler);
+  try {
+    void* x = operator new[](std::numeric_limits<std::size_t>::max());
+    (void)x;
+    assert(false);
+  } catch (std::bad_alloc const&) {
+    assert(new_handler_called == 1);
+  } catch (...) {
+    assert(false);
+  }
+  return 0;
+}