Should I check boost::shared_ptr or std::shared_ptr before I use it?

Question

void f(boost::shared_ptr<int> ptr)
{
    if (ptr) // should we check?
        // do something
}

void f2(int *p)
{
    if (p) // good practice to check before using it
        // do something
}

Question: Should we validate shared_ptr before we use it?

Answer 1

No. If it is in the contract of the function that it must be valid, then the quickest way to bring attention to the fact that the caller has a bug is to crash. Fail as early as you can.

Answer 2

Depends on whether it's actually a possibility during normal program execution that the shared_ptr is null. If not, push the responsibility as a precondition on the user of f and maybe assert(ptr);. Note that it's not only applicable to shared_ptr, but any pointer use really. Although you maybe should just use references here.