A G++ developer uses the G++ compiler, part of the GNU Compiler Collection, to compile and debug C++ code. They write, test, and optimize C++ code, ensuring it adheres to coding standards and is efficient. They use G++ to translate this code into machine language so it can be executed by a computer. The developer also uses the compiler’s debugging tools to identify and fix errors. They may also work on improving the G++ compiler itself, contributing to the open-source GNU project. Thus, they play a crucial role in developing software applications and systems using C++.