Sign in to follow this  
lride

vector subscript out of range

Recommended Posts

lride    674
I have a vector of pointer to entity. I also have a GameWorld class that contains this vector.
[source lang="cpp"]std::vector<Entity*> entities;

GameWorld::GameWorld()
{
entities.push_back(new Character("YOURS", CharacterType::BLACK));
}
GameWorld::~GameWorld()
{
for(auto e: entities)
delete e;
}[/source]

When I close the game I get assertion failure "vector subscript out of range". What did I do wrong?

Edit:
I still get the vector assertion failure even when I changed the std::vector to std::list
I also found out that I can use the std::vector even I don't #include <vector>

OK I solved my problem. The GameWorld object is inside Game class which is a singleton. So the GameWorld is statically allocated.
But when I allocated Game class on stack, it worked fine. I have no idea why.. Edited by lride

Share this post


Link to post
Share on other sites
Radikalizm    4807
[quote name='MarkS' timestamp='1354996283' post='5008579']
Why not use "delete entities;"? The vector destructor takes care of calling the Entity destructor for each object in the list..
[/quote]

The vector will destroy the pointers, but not the objects the pointers are pointing to. Big difference!
Also 'delete entities' wouldn't even work as the entities vector wasn't allocated on the heap. It wouldn't even compile either, as entities is not a pointer type.

Share this post


Link to post
Share on other sites
Radikalizm    4807
[quote name='MarkS' timestamp='1354997809' post='5008591']
Still, doesn't the vector destructor call the object's destructor upon deletion?
[/quote]

A vector does call a destructor for an object it holds when that object is erased, but this vector is storing pointer objects, not Entity objects.
So basically the vector is calling a destructor for the pointer object (which is perfectly legal), but that doesn't mean the destructor for the object the pointer is pointing to gets called or that the memory consumed by the object the pointer is pointing to gets released. Edited by Radikalizm

Share this post


Link to post
Share on other sites
MarkS    3502
[quote name='Radikalizm' timestamp='1354998013' post='5008594']
[quote name='MarkS' timestamp='1354997809' post='5008591']
Still, doesn't the vector destructor call the object's destructor upon deletion?
[/quote]

A vector does call a destructor for an object it holds when that object is erased, but this vector is storing pointer objects, not Entity objects.
So basically the vector is calling a destructor for the pointer object (which is perfectly legal), but that doesn't mean the destructor for the object the pointer is pointing to gets called or that the memory consumed by the object the pointer is pointing to gets released.
[/quote]

That is very interesting! I don't create vectors of pointers, but I'll need to keep that in mind.

Since we are on the subject, why create a vector of pointers in the first place?

Share this post


Link to post
Share on other sites
iMalc    2466
[quote name='lride' timestamp='1354988921' post='5008542']
When I close the game I get assertion failure "vector subscript out of range". What did I do wrong?[/quote]You either corrupted your vector somewhere, or you tried to access outside of its bounds.

[quote]Edit:
I still get the vector assertion failure even when I changed the std::vector to std::list
I also found out that I can use the std::vector even I don't #include <vector>[/quote]Both of those statements are inaccurate.
If you change it to a list then you wont get assert about the vector because it isn't a vector any more. A std::list does not use code from within the std::vector. You're probably just getting the same error from a different piece of the std library. Getting the same behviour probably means that you are going past the end of the container rather than corrupting it.
If code with vector still compiles, then something else you are including is pulling in the vector header for you. You should probably not be relying on that.

If you need your vector to hold pointers for reasons of polymorphism, then you might be better off with a boost ptr_container rather than a vector. Otherwise you should problably just store instances directly rather than pointers. Edited by iMalc

Share this post


Link to post
Share on other sites
lride    674
[quote name='MarkS' timestamp='1355005213' post='5008615']
Since we are on the subject, why create a vector of pointers in the first place?
[/quote]
Because I want to store different kinds of object in the same vector. This can only be done by storing the pointers or references to the object and using polymorphism.
Also, I store pointers to objects in a vector when the object is too expensive to copy. (When you use std::vector::push_back(), the copy of the object gets stored.)
However, this extra copy can be avoided by using c++11 'move', .


[quote name='iMalc' timestamp='1355006671' post='5008620']
Both of those statements are inaccurate.
If you change it to a list then you wont get assert about the vector because it isn't a vector any more. A std::list does not use code from within the std::vector. You're probably just getting the same error from a different piece of the std library. Getting the same behviour probably means that you are going past the end of the container rather than corrupting it.
If code with vector still compiles, then something else you are including is pulling in the vector header for you. You should probably not be relying on that.

If you need your vector to hold pointers for reasons of polymorphism, then you might be better off with a boost ptr_container rather than a vector. Otherwise you should problably just store instances directly rather than pointers.
[/quote]

This is the only place I'm using vector in my entire project. and I've searched #include <vector> in my entire solution and there was none.
But now that I already solved the problem, what is the advantage of using a boost ptr vector instead of using a normal vector Edited by lride

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this