std::unique_ptr for C functions that need free

Question

Think to a C function that return something that must be freed, for example the POSIX\'s strdup(). I want to use that function in C++11 and avoid a

Answer 1

Assuming it makes sense, it is possible to use a similar pattern with non-pointers? For example for the POSIX's function open that returns an int?

Sure, using Howard's Hinnant tutorial on unique_ptr, we can see a motivating example:

// For open
#include 
#include 

// For close
#include 

// For unique_ptr
#include 

int main()
{
    auto handle_deleter = [] (int* handle) {
        close(*handle);
    };

    int handle = open("main.cpp", O_RDONLY);
    std::unique_ptr uptr
        { &handle, handle_deleter };
}

Alternatively you can use a functor instead of a lambda:

struct close_handler
{
    void operator()(int* handle) const
    {
        close(*handle);
    }
};

int main()
{
    int handle = open("main.cpp", O_RDONLY);
    std::unique_ptr uptr
        { &handle };
}

The example can be further reduced if we use a typedef and a "factory" function.

using handle = int;
using handle_ptr = std::unique_ptr;

template 
handle_ptr get_file_handle(T&&... args)
{
    return handle_ptr(new handle{open(std::forward(args)...)});
}

int main()
{
    handle_ptr hp = get_file_handle("main.cpp", O_RDONLY);
}