vector::pop_back & erase problems

**codec** · 03-30-2004

Hi,

I use a vector to hold connection information for each client in my piece of server sofware.

I'm having a problem when removing elements from my vector when clients disconnect.

When I only have one client connected and therefore one element in the vector, is when the problem is most obvious. Everything is fine until I use either vector.pop_back or vector.erase to remove the element (when the client disconnects). Then my program throws what I think is an execption.

This only happens for the last element in the vector. For example, if two clients connect, I can easily remove the element for the first client without a problem. Then, if I attempt to remove the second (which is now the only element), I get an exception.

If you need specific code snippets, please don't hesitate to ask. I just thought this might be a known issue with vectors.

Any help greatly appreciated. Many thanks,

Daniel Briley

**Prelude** · 03-30-2004

>If you need specific code snippets, please don't hesitate to ask.
Give us a small, compilable program that exhibits the problem.

>I just thought this might be a known issue with vectors.
Not to my knowledge. Chances are that you are just doing it wrong.

**codec** · 03-30-2004

First off, thanks for the help

Here's a small program that illustrates my problem, at least when using vector::erase

Code:

#include <vector>

using namespace std;

typedef vector<int> INTVECTOR;
INTVECTOR v_clients;

int main(int argc, char **argv)
{
	INTVECTOR::iterator i;

	v_clients.push_back(10);

	for (i = v_clients.begin(); i != v_clients.end(); i++) {
		v_clients.erase(i);
	}

	return 0;
}

My understanding is that the for loop should just interate through the elements, and remove them all, but it throws an exception. I realise that in this example I could just use pop_back, but this illustrates my problem in my actual program, in which an iterator is passed to the function which handles the connection.

In my actual program, it's not a vector of integers, it's a vector of structs which holds information such as the SOCKET and sockaddr_in structure for the connection.

Daniel

**codec** · 03-30-2004

Forgive me if it's a stupid error that I've made, I'm fairly new to C++ and I'm sure I can easily fall victim to common pitfalls and errors.

Daniel

**Magos** · 03-30-2004

You erase i, then you're trying to call the overloaded ++ operator on it. Not good. However, erase() returns the next iterator so use that instead:

Code:

i = v_clients.begin();
while(i != v_clients.end()
{
  i = v_clients.erase(i);
}

**elad** · 03-31-2004

Alternatively, erase() comes overloaded with another version that takes a range of elements to be erased so you don't need to loop if you don't want to:

v_clients.erase(v_clients.begin(), v_clients.end());

**Magos** · 03-31-2004

Well, doing that he cannot call any functions on each element which he (implicitly) said he wanted. If the intention is to remove all elements, you may as well use v_clients.clear();

**codec** · 03-31-2004

Thanks for the help guys, much appreciated.

Thread: vector::pop_back & erase problems

Thread Tools

Search Thread

Display

vector::pop_back & erase problems

Similar Threads

Question about erase()

No clue how to make a code to solve problems!

C Pointers Problems

contest problems on my site

string erase function problems