In this series we examine the relationship and implementations of C++ and raw assembly code. In this post we create our own add function in gcc extended assembly.
In the previous post we wrote a short C++ program that loaded two numbers. Despite its simplicity in C++, we saw how the assembly version was comprised of several dozen individual instructions in a rather cryptic format. Much of this complexity stems from the fact that in our sample program we called a function to perform our addition. Calling functions means dealing with a stack, base pointers, and the setup and maintenance of that stack. It means dealing with memory offsets, relative positions, and several other factors. The good news is that at this point we can safely ignore these details. In fact, we will do well to ignore them and focus on just the core competencies of function implementation code. In other words, we’ll let gcc create the function shells, calls, and stack management, we’ll focus on the core logic.