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Trace Source Code to an Executable

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EasySoftware EngineerTechnical ScreenSoftware Engineering Fundamentals

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This question tests the candidate's understanding of the C/C++ compilation pipeline, focusing on how source code is transformed into a runnable binary and the role of different build artifacts.

The Compilation Lifecycle

Explain the transformation process of a C++ source file (main.cpp) into a final executable binary. Describe the purpose and output of each of the following four stages:

  1. Preprocessing
  2. Compilation
  3. Assembly
  4. Linking

Theoretical Task

Suppose you have a project with two files: math_utils.cpp (which contains a function int add(int a, int b)) and main.cpp (which calls add).

  • What is the difference between an object file (.o) and an executable?
  • If you successfully compile both files but receive an "undefined reference to add" error during the linking phase, what is the most likely cause?
  • Explain what happens to the program's virtual memory when you execute the resulting binary in a modern OS.

Hints

Hint 1

Think about how the compiler handles `#include` statements and macro definitions before it begins translating code into machine instructions.

Hint 2

Consider the difference between a declaration (header file) and a definition (implementation file) and how the linker resolves these addresses.

Hint 3

Recall that an object file contains machine code for a specific unit, but it still has unresolved placeholders for external symbols that the linker must patch.

Follow-up questions

  • What is the difference between static linking and dynamic linking, and how do they affect the final size and portability of the executable?
  • How does the OS loader use the Program Header Table of an ELF file to prepare the process for execution?
  • What are symbols, and why are they sometimes stripped from a production binary?