Returning a local object results in garbage, while returning the same object temporary works fine

[bl9009]

Hello,

I'm currently implementing my own string class (just for training), but I'm experiencing some problems in my substr() method:

MyString MyString::substr(size_t position, size_t length)
{
    if (checkBounds() || length == 0)
    {
        return MyString();
    }

    char* tmp = new char[length + 1];

    memcpy(tmp, this->s + position, length);

    tmp[length] = STRING_ESCAPE;

    MyString result(tmp);

    delete[] tmp;
    tmp = nullptr;

    return result;
}

When I call this method and print the return value (I'm printing the char array actuallay, not the object itself), I receive complete garbage, which is carried out as a bunch of squares.

But when I return a temporary object return MyString(tmp), everything works fine. Initially i suspected this issue is associated to the delete[] operation, but commenting it out shows no effect.

The MyString constructor which is called is the following:

MyString::MyString(const char* s)
{
    size_t length = this->strlen(s);

    this->sLength = length;

    this->s = new char[length + 1];

    for (size_t i = 0; i <= length; ++i)
    {
        this->s[i] = *s;

        ++s;
    }
}

So where is my mistake? Thank you!

[rich1]

Suppose I have MyString str("Hello"). When I call str.substr(0, 10). What will happen?

[bl9009]

it returns an empty string, simply ""

[Disch]

Looks like you are creating the temporary just fine. The problem might be in your copy constructor. Can you post that for us? (if you have a move constructor, can you post that as well?)