CODEWITHSUNDEEP
c++oopmemory-managementconstructorstack
user3144334
user3144334

Reputation: 135

Issue in allocating memory for resizing stack

I have tried and tried to figure the mistake in my code , but I still can't find it.I have a Stack class Album, which i want to resize, and think i did it right.For some reason however most of the times the program crashes and maybe one in 10 works fine and I have no idea why.If you could point the mistake that would be great. So here is the code:

const Song Song::null_song;//static from Song class

class Album
{
    Song* songs;
    char* name;
    int top;
    int capacity;
    bool full () const;
    void resize ();

public:
    ...
}

And here are the functions, somewhere in them is the culprit.The problem happens when I try to push more items in Album then the predefined INIT_CAPACITY=4.I think it should work, but it doesn't, so the problem must be allocating the new memory. 

const int INIT_CAPACITY=4;

std::ostream& operator<<(std::ostream& os, Album& p)
{
    os<<"Name of Album:"<<p.name<<std::endl;
    for(int i=0;i<=p.top;i++)
        os<<p.songs[i]<<std::endl;
}

Album::Album(const char* p)
{
    int len1=strlen(p);
    name=new char [len1+1];
    strcpy(name,p);
    top=-1;
    songs = new Song[INIT_CAPACITY];
    capacity = INIT_CAPACITY;
}

Song Album::pop()
{
    if (empty())
        return Song::null_song;
    return songs[top--];
}

Song Album::last() const
{
    if (empty())
        return Song::null_song;
    return songs[top];
}

bool Album::push(Song x)
{
    if (full())
        resize();
    songs[++top] = x;
    return true;
}

void Album::resize()
{
    capacity *= 2;
    Song* newsongs = new Song[capacity];
    for(int i = 0; i < capacity / 2; i++)
        newsongs[i] = songs[i];
    delete[] songs;
    songs = newsongs;
}

bool Album::empty() const
{
    return top == -1;
}

bool Album::full() const
{
    return top == capacity-1;
}

Album::Album()
{
    top=-1;
    songs = new Song[INIT_CAPACITY];
    capacity = INIT_CAPACITY;

    name=new char [1];
    name[0]='\0';
}

Album::~Album()
{
    delete [] songs;
    delete [] name;
}

Upvotes: 1

Views: 74

Answers (1)

molbdnilo
molbdnilo

Reputation: 66371

Your Song also uses char* where it should use std::string.

It deletes this pointer in the destructor, but you haven't defined an assignment operator or copy constructor.

This makes all Songs contain invalid pointers once you have resized an Album.

Upvotes: 1

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