Pass Vector by reference and Get Error - c++

Question

Following code is for test the pass the reference of a vector to a function. However, it will have some unknown fault. I got the error message from gdb as following:
Source is:
#include<iostream>
#include<vector>
using namespace std;
class ROLE
{
public:
ROLE(int);
int HP;
};
ROLE::ROLE (int input)
{
HP = input;
}
void checkVector(vector<ROLE>&input);
int main()
{
vector<ROLE> R;
ROLE K(102);
R.push_back(K);
K.HP = 111;
R.push_back(K);
checkVector(R);
return 1;
}
void checkVector(vector <ROLE> & input)
{
cout<<"size of vector "<<input.size()<<endl;
for(int i =0; i<input.size();i++)
{
cout<< input[i].HP<<endl;
}
}
I can't find the reason of the error. Any idea is appreciated!
I realized that error probably from the push_back, because I also get the error if I modified the code as following. Are there any idea about what happened?
#include<iostream>
#include<vector>
using namespace std;
class ROLE
{
public:
ROLE(int);
int HP;
};
ROLE::ROLE (int input)
{
HP = input;
}
int main()
{
vector<ROLE> R;
ROLE K(0);
K.HP=1;
R.push_back(K);
K.HP = 113;
R.push_back(K);
K.HP = 111;
R.push_back(K);
return 0;
}
Possible answer:
I get one way which can avoid the error.
Following is the no-error source.
#include<iostream>
#include<vector>
using namespace std;
class ROLE
{
public:
ROLE(int);
void constructAry(int inputHP);
int HP;
};
ROLE::ROLE (int input)
{
HP = input;
}
void ROLE::constructAry(int inputHP)
{
HP = inputHP;
}
void checkVector(vector<ROLE>&input);
int main()
{
vector<int> test;
vector<ROLE> R;
ROLE K(0);
K.constructAry(1);
R.push_back(K);
K.constructAry(2);
R.push_back(K);
K.constructAry(3);
R.push_back(K);
K.constructAry(4);
R.push_back(K);
checkVector(R);
return 1;
}
void checkVector(vector <ROLE> & input)
{
cout<<"size of vector "<<input.size()<<endl;
for(int i =0; i<input.size();i++)
{
cout<< input[i].HP<<endl;
}
}
So it seems that using a constructor-like function to modify the value of the same object and push_back the object in the vector can effectively avoid the bug.
The reason is ambiguous for me. Maybe the memory address's matter.