strange behavior of vector template iterator

[nicolaennio]

I am new with c++ and I cannot understand why this code:

#include <cstdlib>
#include <iostream>
#include <vector>
 
using namespace std;
 
vector<int>::iterator _begin(vector<int> v){
    return v.begin();
}
 
int main(int argc, char *argv[])
{
    vector<int> v;
    v.push_back(4);
    vector<int>::iterator b = _begin(v);
    printf("%d\n",*b);
    printf("%d\n",*_begin(v));
 
    system("PAUSE");
    return EXIT_SUCCESS;
}
 

gives me this output:
0
4

thanks

[willakawill]

Well I get -17890612 for both. And this is not beginner stuff :)

[nicolaennio]

thanx for trying it out, actually I am not a beginner in programming, but in c++ yes and I have some difficulties.
I tried it at home and I get something like
40546540
4
Since code is small I could code around this problem, but I need using vector rather than stack and hope it is a problem like "say to the compiler what template you use and ... (it will say who you are :-) )".
It is strange that in your case neither printf worked

[nicolaennio]

ok, I find out the problem, since vector I pass in input is by value a copy is made
in the function and iterator work on the copy, so I return a useless iterator.
I don't know why on my machine it printed 0 rather than an impossible value as willakawill.

[willakawill]

Excellent work. Glad you found it