Don't pass a pointer that may be invalid (dangling) as a parameter to a function.

void use(int*);

void ex1()
{
    int* px;
    {
        int x;
        px = &x;
    }

    use(px);  // px is a dangling pointer
}

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:

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

• C++ Core Guidelines Lifetimes Paper