unique_ptr<T> lambda custom deleter for array specialization [duplicate]

Question

I recently started porting lots of my existing C++ application code to over to C++11 and now that I am converting to the new smart pointers std::unique_ptr and std::shared_ptr, I have a specific question about custom deleters. I want to add a lambda logger to see where my deletes are being called but I cannot get the array specialization version to compile. Advice would be very much appreciated.

I have been searching in vain for an example of a custom deleter for array specialization unique_ptr for VC++10 or GCC 4.5.2+. I would like to print a log message when the deleters are called in a lambda - mainly to make sure that all the pointers that I think are going out of scope are doing so. Is this possible for the array version of the specialization? I can get it to work with the non array version, and I can also get it to work with an array specialization if I pass an external struct "MyArrayDeleter" as the second argument. One more thing, would it be possible to remove the ugly std::function as I thought that I could let the lambda signature figure that out.

struct MySimpleDeleter {     void operator()(int* ptr) const {         printf("Deleting int pointer!\n");         delete ptr;     } }; struct MyArrayDeleter {     void operator()(int* ptr) const {         printf("Deleting Array[]!\n");         delete [] ptr;     } }; {     // example 1 - calls MySimpleDeleter where delete simple pointer is called     std::unique_ptr<int, MySimpleDeleter> ptr1(new int(5));      // example 2 - correctly calls MyArrayDeleter where delete[] is called     std::unique_ptr<int[], MyArrayDeleter> ptr2(new int[5]);      // example 3 - this works (but default_delete<int[]> would have been passed     // even if I did not specialize it as it is the default second arg     // I only show it here to highlight the problem I am trying to solve     std::unique_ptr<int[], std::default_delete<int[]>> ptr2(new int[100]);      // example 3 - this lambda is called correctly - I want to do this for arrays     std::unique_ptr<int, std::function<void (int *)>> ptr3(         new int(3), [&](int *ptr){              delete ptr; std::cout << "delete int* called" << std::endl;          });      // example 4 - I cannot get the following like to compile     // PLEASE HELP HERE - I cannot get this to compile     std::unique_ptr<int[], std::function<void (int *)>> ptr4(         new int[4], [&](int *ptr){               delete []ptr; std::cout << "delete [] called" << std::endl;          }); }  The compiler error is as follows:  The error from the compiler (which complains about the new int[4] for ptr4 below is: 'std::unique_ptr<_Ty,_Dx>::unique_ptr' : cannot access private member declared in class 'std::unique_ptr<_Ty,_Dx>' 1>          with 1>          [ 1>              _Ty=int [], 1>              _Dx=std::tr1::function<void (int *)> 1>          ] 1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\memory(2513) : see declaration of 'std::unique_ptr<_Ty,_Dx>::unique_ptr' 1>          with 1>          [ 1>              _Ty=int [], 1>              _Dx=std::tr1::function<void (int *)> 1>          ] 

Answer 1

What about:

auto deleter=[&](int* ptr){...}; std::unique_ptr<int[], decltype(deleter)> ptr4(new int[4], deleter);