What are some possible vulnerabilities with integers and functions in the C++ iostream library?

What are locks in C++? What are they used for?

One optional formal parameter of C++ main() is envp. Explain its type and function. Is it helpful to have an addition int parameter (like argc) to specify the number of elements in envp?

In creating C++ applications, you have the ability to utilize various formatting functions in the iostream library. What are some of the formatting vulnerabilities that can be encountered in using the iostream library in C++? What tips can be utilized to identify these vulnerabilities? Be sure to provide an appropriate source code example to illustrate your points.