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Asked: 2026-05-19T02:22:17+00:00

I understand that placement new calls are usually matched with explicit calls to the

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I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call?

Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want
to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods.

I have two parts to this question.

  1. Is there any reason why this idea will not work in practice on any production compiler?

  2. Does this technically violate the C++ language spec?

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1 Answer

  1. Editorial Team

    If I understand your question correctly you have a C object in memory and you want to initialize a C++ object with the same layout “over the top” of the existing object.

    CppObject* cppobject = new (cobject) CppObject;

    While there is no problem with not calling a destructor for the old object – whether this causes resource leaks or other issues is entirely down to the type of the old object and is a user code issue, not a language conformance issue – the fact that you reuse the memory for a new object means that the old object is no longer accessible.

    Although the placement form of operator new must just return the address that it was given, there is nothing to stop the new expression itself wiping the memory for the new object before any constructor (if any) is called. Members of the new object that are not initialized according to C++ language rules have unspecified contents which definitely does not mean the same as having the contents of any old object that once lived in the memory being reused.

    If I understand you correctly, what you are trying to do is not guaranteed to work.

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