Numerous C++ questions

Komakino · 07-06-2004, 01:29 PM

Hey peeps,

I have a couple of (fairly simple) C++ questions I'd like answered, if you'd be so kind:

1. If I have a method within a class that creates a pointer to an object using the new keyword, can it return a pointer to that object or is it lost on procedure exit?
For example:

Code:

// Incomplete code...
SDL_Surface *temp;
SDL_Surface* getFrame(){
    temp = SDL_CreateRGBSurface(...etc....);
    return temp;
}

Is that valid or is temp lost?

2. Does EVERYTHING I create using new need a corresponding delete statement? Until recently I believed that it was only things of indeterminate size (for example created using malloc) that needed freeing or deleting, but looking around it seems this is not the case, and now in every class's destructor I have several delete statements to cater for the numerous objects created within the class. Is this right?

That's all folks! I'm not new to programming, I've been a Java programmer for years, but C++ is throwing up some interesting new challenges for me.

Thanks!

Kk

deveraux83 · 07-06-2004, 01:38 PM

The code you have written seems correct althought you should be very careful how the pointer returned by getFrame() is treated. If delete is called upon it and somewhere else in the program you try to operate on temp, you might get a segmentation fault error. Also, remember that if later on in the program another method from your class (I'm assuming temp is a variable in your class) accesses temp, the memory its pointing to might have been changed as you are allowing functions outside your class access its memory location by parsing the pointer.

As to your enquiry about a new being "accompanied" by a delete, the answer is YES. Anytime you allocate an object(s) with new you SHOULD deallocate it when you're done with the object(s) or it could lead to memory leaks.

Komakino · 07-06-2004, 01:42 PM

Thanks, yes temp is a class variable. As everything gets deleted at once, there should be no problem in this instance of other classes accessing it after deletion.

p.s. I notice how you answered my thread and I answered yours....I just hope my answer is what you're looking for!