C++ code compilation with Unreal Engine

The compilation process with Unreal Engine involves additional steps than compiling pure C++ code. The reason is that Unreal provides us with some decorators that help us write less code and keep the files cleaner, and this requires an extra step, namely the Unreal Header Tool, which basically translates these decorators into C++ code.

Compilation Steps

Unreal Header Tool

This tool is responsible for getting all the unreal specific syntax and translating it into C++ code. Syntax like UPROPERTY, UCLASS, GENERATED _BODY is converted to C++ code.

Preprocessor

This preprocesses the code by adding the appropriate C++ header code at the point where we insert #include. Using #pragma once ensures that no duplicate code is inserted into the compiled version.

Compiler

Get the C++ code .i, which is the preprocessed version and is individually compiled to binary code.

Linker

This merges all linked and necessary dependencies to create an executable file

Linkers, Headers and Includes

This process seems complicated, but the reason is that the compiler does not have to recompile the math.obj file if the change is made only in game.cpp, which speeds up compilation time.