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It is acceptable to define a deleted allocation or deallocation function without its corresponding free store function. For instance, it is a common practice to define a deleted non-placement allocation or deallocation function as a class member function when the class also defines a placement new function. This prevents accidental allocation via calls to new for that class type , or deallocation via calls to delete on pointers to an object of that class type. It is acceptable to declare, but not define, a private allocation or deallocation function without its corresponding free store function for similar reasons. However, a definition must not be provided as that still allows access to the free store function within a class member function.

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In this compliant solution, the corresponding deallocation function is also defined at global scope:.

#include <Windows.h>
#include <new>

class HeapAllocator {
  static HANDLE h;
  static bool init;
 
public:
  static void *alloc(std::size_t size) noexcept(false) {
    if (!init) {
      h = ::HeapCreate(0, 0, 0); // Private, expandable heap.
      init = true;
    }
 
    if (h) {
      return ::HeapAlloc(h, 0, size);
    }
    throw std::bad_alloc();
  }
 
  static void dealloc(void *ptr) noexcept {
    if (h) {
      (void)::HeapFree(h, 0, ptr);
    }
  }
};
 
HANDLE HeapAllocator::h = nullptr;
bool HeapAllocator::init = false;

void *operator new(std::size_t size) noexcept(false) {
  return HeapAllocator::alloc(size);
}
 
void operator delete(void *ptr) noexcept {
  return HeapAllocator::dealloc(ptr);
}

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In this compliant solution, the corresponding operator delete() is overloaded at the same class scope:.

#include <new>

extern "C++" void update_bookkeeping(void *allocated_ptr, std::size_t size, bool alloc);

struct S {
  void *operator new(std::size_t size) noexcept(false) {
    void *ptr = ::operator new(size);
    update_bookkeeping(ptr, size, true);
    return ptr;
  }
 
  void operator delete(void *ptr, std::size_t size) noexcept {
    ::operator delete(ptr);
    update_bookkeeping(ptr, size, false);
  }
};

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Mismatched usage of new and delete could lead to a denial-of-service attack.

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Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

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Bibliography

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