Don't dereference a pointer that may be null.

void ex1()
{
    int* px = nullptr;

    if (px)       // notice the condition is incorrect
        return;

    *px = 1;      // 'px' known to be null here
}

The Lifetime guidelines from the C++ core guidelines outline a contract that code can follow which will enable more thorough static memory leak and dangling pointer detection. The basic ideas behind the guidelines are:

1. Never dereference an invalid (dangling) or known-null pointer
2. Never return (either formal return or out parameter) any pointer from a function.
3. Never pass an invalid (dangling) pointer to any function.

• C++ Core Guidelines Lifetimes Paper