Deconstruct const pointer?

Question

It's probably very basic but I am stuck and simply don't know what the problem is.

The main code is predefined as a task. The goal is to use const as much as possible. The following constructor is just supposed to copy the literal string to the const m_data and that works fine but I am not able to free the memory - it always leaves 1 block. What am I missing?

main.cpp

#include <iostream>
#include "immstring.hpp"
using namespace std;
using namespace Util;

int main() 
{
  const ImmutableString s1("Hello");
}

immu.hpp

#include <cstring>
namespace Util {
class ImmutableString {
public:
    ImmutableString(const char* src);
    ~ImmutableString();

private:
    char* const m_data;
};
}

immu.cpp

#include "immstring.hpp"
#include <iostream>
#include <cstring>
namespace Util 
{
ImmutableString::ImmutableString(const char* src)
    :m_data{strcpy(new char[strlen(src)+1],src)}{}

ImmutableString::~ImmutableString() 
{
    delete m_data;
}
}

And better yet, [avoid `new` and `new[]`](https://stackoverflow.com/q/6500313/10077). — Fred Larson, May 09 '18 at 14:07
Note that `char* const m_data` is not an immutable character string. It's an immutable pointer to a mutable character string. You likely want `const char* m_data;`. — François Andrieux, May 09 '18 at 14:08
That is true the title is a little misleading - although I tried delete [] m_data and still get: still reachable: 72,704 bytes in 1 blocks — dustinboettcher, May 09 '18 at 14:14
Is `s1` global or in the scope of `main`? Please share a [MCVE]. — François Andrieux, May 09 '18 at 14:15
Note that "still reachable" doesn't necessarily mean there was a memory leak problem -- it might be deliberate. https://stackoverflow.com/questions/3840582/still-reachable-leak-detected-by-valgrind?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa — Jeremy Friesner, May 09 '18 at 14:22
That's it - I was so focused on the getting a clean log that I didn't notice that delete [] provided no errors - "just" the 1 block. Thanks everyone this was driving me nuts. — dustinboettcher, May 09 '18 at 14:30

score 1 · Accepted Answer · answered May 09 '18 at 14:33

1

To leave all array memories blocks you have to use delete like this :

delete[] m_data;

Thanks, Robin.

answered May 09 '18 at 14:33

Robin M.

66
3

Deconstruct const pointer?

1 Answers1