CODEWITHSUNDEEP
c++
user44322
user44322

Reputation: 361

Automatically initialized?

The beginning of my class is:

class Player{
private:
    Cardpile hand;
    ...
}

Where Cardpile is another class. If I do Player *p=new Player(); Is hand automatically initialized? I am asking this because I been trying to figure out a segmentation fault. I have looked everywhere in my code. The last thing I can think of is that hand is not initialized.

EDIT: This is the segmentation error I got. Card is a class inside of Cardpile. I know Card and Cardpile both works.

Program received signal SIGSEGV, Segmentation fault.
0x0000000000402ac0 in __gnu_cxx::new_allocator<Card*>::construct (this=0x6070a8, __p=0x4015c6, __val=@0x7fffffffe6d8) at /usr/include/c++/4.4/ext/new_allocator.h:105
105           { ::new((void *)__p) _Tp(__val); }

EDIT: Cardpile class:

class Cardpile : private vector<Card*> {
    public:
    using vector<Card*>::size;
    using vector<Card*>::at;
    Cardpile ();
...
}
Cardpile::Cardpile(){}

EDIT: Here is a cool fact: p==NULL does not check if p is initiated. I guess that's why I keep getting segmentation fault.

Upvotes: 4

Views: 172

Answers (2)

Olaf Dietsche
Olaf Dietsche

Reputation: 74058

If you don't explicitly member initialize hand in your Player constructor, then the default constructor of Cardpile will be used.

If you haven't defined a default constructor, the compiler will create one.

When you compile and link your program with -g, gdb can show the stacktrace where your program crashed:

gdb program core

and then inside gdb enter bt. This will show the complete call stack at time of the segmentation fault.

Upvotes: 3

Luchian Grigore
Luchian Grigore

Reputation: 258618

It depends on what Cardpile is. If it's a POD, then no:

class Cardpile1{
   int x;
};

If it's not, then yes:

class Cardpile2{
   Cardpile2() : x(0) {}
   int x;
};

hand will exist for both cases, but reading from it is illegal if Cardpile is defined as a POD.

class Player{
  public:
    Cardpile1 hand1;
    Cardpile2 hand2;
};

Player p;
p.hand1.x;   //illegal
p.hand2.x;   //legal

Upvotes: 3

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