terminate called after throwing an instance of 'pqxx::broken_connection'

Question

When I create an array of connections to psql database using pqxx, connections create successfully and they are in the array. But when I'm going to use one connection it gives me the following error. The way i created the array is also mentioned below. Can anyone tell me the reason for this.

for(int i=0;i<10;i++)
    {

        connection c("dbname=test user=postgres password=abc123\
                     hostaddr=127.0.0.1 port=5432");
        conList[i]=&c;
    }

  for (int j=0;j<10;j++)
        {
            cout<<conList[j]->is_open()<<endl; // this returns 0
        }

conList[0]->activate(); // at this point it gives the following error

terminate called after throwing an instance of 'pqxx::broken_connection' what(): Connection to database failed Aborted

Answer 1

You are storing address of local variable c in conList, after first for loop, those local variables are released, conList stores dangling pointers only, invoke function call to dangling pointers has undefined behavior.

for(int i=0;i<10;i++)
{

    connection c("dbname=test user=postgres password=abc123\
                 hostaddr=127.0.0.1 port=5432");
    conList[i]=&c;  // c is local variable
}   // c is released here

for (int j=0;j<10;j++)
{
    cout<<conList[j]->is_open()<<endl;  // undefined behavior
}

conList[0]->activate(); // undefined behavior

Consider below change?

store value instead of pointer in conList

for(int i=0;i<10;i++)
{

    connection c("dbname=test user=postgres password=abc123\
                 hostaddr=127.0.0.1 port=5432");
    conList[i] = c;  // make a copy of c
}   

for (int j=0;j<10;j++)
{
    cout<<conList[j].is_open()<<endl;  
}

conList[0].activate();