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std::vector::clear()

Started by Supernat02 Nov 7, 2004 at 12:19 AM 4 replies 1.9k views

Original Post

Nov 7, 2004 at 12:19 AM

I use the vector class to store pointers instead of entire classes, so that I can do the memory management myself and not have to copy an entire class when adding it to the vector. I'm not completely familiar with STL yet, so I may misunderstand it altogether. Anyhow, I create the vector with a pointer to a structure. When I call insert(), I pass the pointers in. What happens when I call vector::clear()? According to what I've read, it calls the destructors for classes. I'm a little confused about what memory management will take place with the call to clear(). I want to make sure I get the used memory de-allocated. I think it will just de-allocate the memory used to store the pointers, but I still have to destroy the referenced object. Is this true? Thanks in advance. Chris

Bincho

Nov 7, 2004 at 12:28 AM

You're going to have to manually delete each pointer. When you add an object to the vector class (not as a pointer, but actually adding an object) it will call the destructor of it when the vector itself is deleted or goes out of scope.

Rayno

Nov 7, 2004 at 12:31 AM

Quote:
Original post by Supernat02
I use the vector class to store pointers instead of entire I want to make sure I get the used memory de-allocated. I think it will just de-allocate the memory used to store the pointers, but I still have to destroy the referenced object. Is this true?

Yeah, thats true. If you used new to allocate memory for whatever your pointers point to, then you need to call delete yourself.

Or you could use something like auto_ptr, or boost::smart_ptr, and you wouldn't have to worry about it.

desertcube

Nov 7, 2004 at 4:53 AM

Quote:
Original post by Rayno
Or you could use something like auto_ptr, or boost::smart_ptr, and you wouldn't have to worry about it.

I agree about using smart pointers to take care of your memory, such as the boost one's you mentioned or Loki's (from Modern C++ Design, excelent book btw!), but you can not use auto_ptr!

Another alternative would be to impliment your own smart_ptr based on the above two libraries. Very easy to do and takes the worries about memory managment away (if used correctly).

Supernat02

Author

Supernat02

Nov 7, 2004 at 9:23 PM

Thanks everyone for confirming what I was thinking. :)

Chris

Rayno

Nov 7, 2004 at 11:02 PM

Quote:
Original post by desertcube
but you can not use auto_ptr!

Thanks for pointing that out. I didn't know that. I had always just used the boost pointers.

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