CODEWITHSUNDEEP
c++c++11runtime-errorunique-ptr
user3798283
user3798283

Reputation: 467

run time error with unique_ptr

The below code results in run time error. Obviously when unique_ptr a goes out of scope it tries to delete the memory which has already been deleted, so causes a heap issue. My question is what changes I should do in Line X as highlighted as they share same memory and there won't be any runtime error either even after using delete call.

#include <iostream>
#include <memory>
using namespace std;
int main () 
{
    int* p = new int (10);
    unique_ptr<int> a (p);   // Line X
    delete p;
    return 0;
}

Upvotes: 1

Views: 430

Answers (2)

eold
eold

Reputation: 6052

Starting with C++14, your snippet can be fixed as follows:

#include <iostream>
#include <memory>
using namespace std;
int main ()
{
    auto a = make_unique<int>(10);   // = unique_ptr<int>(new int(10))
    return 0;
}

Upvotes: 0

jotik
jotik

Reputation: 17920

On line X, you're transferring the ownership of the object pointed to by p to the created unique_ptr<int> a. You should not explicitly delete it later, otherwise you have a double deletion error.

If you don't want the unique_ptr to delete the object it points to, you should release it before destruction, e.g:

int main() {
    int * p = new int(10);
    unique_ptr<int> a(p);
    a.release(); // <--- Release ownership of the integer
    // unique_ptr a no longer "owns" the integer
    delete p;
}

The whole point of unique_ptr is that it "owns" and object and frees its resources in a RAII manner.

Upvotes: 2

Related Questions