Binary Comptability

Question 1

What is binary compatibility?

Answer 1

A program using the older version of a header file continues to work with the newer versions of the header.

Question 2

What is source compatibility?

Answer 2

A program works when recompiled but not modifications to the source code are required.

Question 3

What is a programs API?

Answer 3

Application Programming Interface: The functions, classes, types, etc, that are publicly defined in source code that components outside the program cant use.

Question 4

What does the application Binary interface do?

Answer 4

The same thing as an API but at a binary level.
- The binary interface between two components
- Defines how data structures and routines are accessed in machine code
- The outcome of the compilation process

Question 5

What is binary compatibility in terms of ABI?

Answer 5

Keeping the ABI consistent between builds of your program/library

Question 6

What can you do in order to be binary compatibile?

Answer 6

• Add new non-virtual functions
• Add new Enums
• Reimplement an existing virtual function.
• Add static members

Question 7

What cannot you do if you want to be binary comptabile?

Answer 7

• Change existing function/class member signatures
• Add a virtual function to a class without any, or add a virtual function a parent virtual class
• Change the order of virtual functions.
• Change template arguments

Question 8

What is the PImpI idiom?

Answer 8

An approach in which header files store the public API for our class.
A separate implementation-only class handled inner details. The API class stores a Pointer to this separate private implementation.

Question 9

What is the aim of PImpl?

Answer 9

To create a public API for your class that can be consistently defined in its header file.

Question 10

Why do PImpl?

Answer 10

To avoid large recompilation especially for larger projects.