From 9f56e3d8a5c97ba379f9d79335ac6f4287121611 Mon Sep 17 00:00:00 2001
From: Piotr Pryga <piotr.pryga@nordicsemi.no>
Date: Thu, 15 Sep 2022 18:47:05 +0200
Subject: [PATCH] cpp: Add C++20 [[nodiscard]] attribute to operator new

C++20 standard added [[nodiscard]] attribute to operator new
definitions. In case value returned by operator new is ignored,
compiler emits a warning.

The commit adds the attribute to operator new definitions.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>
---
 subsys/cpp/cpp_new.cpp | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/subsys/cpp/cpp_new.cpp b/subsys/cpp/cpp_new.cpp
index 4a2c0044602..899ffc3bbfe 100644
--- a/subsys/cpp/cpp_new.cpp
+++ b/subsys/cpp/cpp_new.cpp
@@ -13,45 +13,51 @@
 #define NOEXCEPT noexcept
 #endif /* __cplusplus */
 
-void* operator new(size_t size)
+#if __cplusplus < 202002L
+#define NODISCARD
+#else
+#define NODISCARD [[nodiscard]]
+#endif /* __cplusplus */
+
+NODISCARD void* operator new(size_t size)
 {
 	return malloc(size);
 }
 
-void* operator new[](size_t size)
+NODISCARD void* operator new[](size_t size)
 {
 	return malloc(size);
 }
 
-void* operator new(std::size_t size, const std::nothrow_t& tag) NOEXCEPT
+NODISCARD void* operator new(std::size_t size, const std::nothrow_t& tag) NOEXCEPT
 {
 	return malloc(size);
 }
 
-void* operator new[](std::size_t size, const std::nothrow_t& tag) NOEXCEPT
+NODISCARD void* operator new[](std::size_t size, const std::nothrow_t& tag) NOEXCEPT
 {
 	return malloc(size);
 }
 
 #if __cplusplus >= 201703L
-void* operator new(size_t size, std::align_val_t al)
+NODISCARD void* operator new(size_t size, std::align_val_t al)
 {
 	return aligned_alloc(static_cast<size_t>(al), size);
 }
 
-void* operator new[](std::size_t size, std::align_val_t al)
+NODISCARD void* operator new[](std::size_t size, std::align_val_t al)
 {
 	return aligned_alloc(static_cast<size_t>(al), size);
 }
 
-void* operator new(std::size_t size, std::align_val_t al,
-		   const std::nothrow_t&) NOEXCEPT
+NODISCARD void* operator new(std::size_t size, std::align_val_t al,
+			     const std::nothrow_t&) NOEXCEPT
 {
 	return aligned_alloc(static_cast<size_t>(al), size);
 }
 
-void* operator new[](std::size_t size, std::align_val_t al,
-		     const std::nothrow_t&) NOEXCEPT
+NODISCARD void* operator new[](std::size_t size, std::align_val_t al,
+			       const std::nothrow_t&) NOEXCEPT
 {
 	return aligned_alloc(static_cast<size_t>(al), size);
 }