When i run valgrind on below program, it reports memory leak. Can you please explain the cause?
#include <string>
#include <iostream>
using namespace std;
int main()
{
char * arr = (char *) ::operator new(sizeof(char));
string s = arr;
return 0;
}
valgrind is right. You call new and don't call delete, hence you have a memory leak.
When you assign arr to s, the latter doesn't take ownership of the former; instead, it makes a copy. It is still your responsibility to free arr.
Ownership of arr is not passed to s, it copies arr to s's internal buffer. You should free memory with delete operator
I think you assumed string will take the ownership of arr and it's responsible for delete the arr. BUT IT IS WRONG.
string s = arr;
Just copies characters from arr until reaching to \0. So, you should delete arr yourself.
delete arr at end of your code will handle memory leak.
The new[] operator in C++ allocates memory dynamically. All such memory must be freed manually, by the programmer. This is done with the delete[] operator. If you don't delete memory which you allocated with new, you have created a memory leak.
More information on that topic can be found in this C++ FAQ.
std::stringwill not magically free your array