Most of the time, working in cybersecurity, when we're reverse engineering an application we're working either with C or C++. Both of these languages use function semantics for method or function calls. Objective C is different — instead of using function semantics, where you use a 'call' instruction to pass program execution and state to a specific section of memory, Objective C uses message passing semantics. Let's explore exactly what that is, and how it differs from function semantics. We'll start by outlining exactly what function semantics are and how they work. To do that, we'll need to outline use of the call instruction and name mangling in C++.
C code is pretty straightforward to analyze. A function call in C will look something like this: