[utils] add a flag to use std new (#11937)

The noexcept placement new is standard in c++11. This commit adds a
config OPENTHREAD_CONFIG_USE_STD_NEW to allow using <new>. The default
behavior is still using OpenThread's own placement new implementation.

src/core/config/misc.h

@@ -617,6 +617,15 @@
 #define OPENTHREAD_EXAMPLES_SIMULATION 0
 #endif
 
+/**
+ * @def OPENTHREAD_CONFIG_USE_STD_NEW
+ *
+ * Define 1 to enable using std <new>.
+ */
+#ifndef OPENTHREAD_CONFIG_USE_STD_NEW
+#define OPENTHREAD_CONFIG_USE_STD_NEW 0
+#endif
+
 /**
  * @}
  */

src/include/common/new.hpp

@@ -34,10 +34,16 @@
 #ifndef OT_INCLUDE_COMMON_NEW_HPP_
 #define OT_INCLUDE_COMMON_NEW_HPP_
 
+#include <openthread/config.h>
+
+#if defined(OPENTHREAD_CONFIG_USE_STD_NEW) && OPENTHREAD_CONFIG_USE_STD_NEW
+#include <new> // IWYU pragma: keep
+#else
 #include <stddef.h>
 
 #include <openthread/platform/toolchain.h>
 
 inline void *operator new(size_t, void *p) throw() { return p; }
+#endif
 
 #endif // OT_INCLUDE_COMMON_NEW_HPP_

tests/CMakeLists.txt

@@ -29,6 +29,7 @@
 option(OT_BUILD_GTEST "enable gtest")
 
 if(OT_FTD AND BUILD_TESTING AND (NOT OT_PLATFORM STREQUAL "nexus"))
+    target_compile_definitions(ot-config INTERFACE "OPENTHREAD_CONFIG_USE_STD_NEW=1")
     add_subdirectory(unit)
     if(OT_BUILD_GTEST)
         add_subdirectory(gtest)

tests/unit/test_platform.cpp

@@ -26,8 +26,6 @@
  *  POSSIBILITY OF SUCH DAMAGE.
  */
 
-// Disable OpenThread's own new implementation to avoid duplicate definition
-#define OT_INCLUDE_COMMON_NEW_HPP_
 #include "test_platform.h"
 
 #include <map>