Book Image

Extreme C

By : Kamran Amini
5 (1)
Book Image

Extreme C

5 (1)
By: Kamran Amini

Overview of this book

There’s a lot more to C than knowing the language syntax. The industry looks for developers with a rigorous, scientific understanding of the principles and practices. Extreme C will teach you to use C’s advanced low-level power to write effective, efficient systems. This intensive, practical guide will help you become an expert C programmer. Building on your existing C knowledge, you will master preprocessor directives, macros, conditional compilation, pointers, and much more. You will gain new insight into algorithm design, functions, and structures. You will discover how C helps you squeeze maximum performance out of critical, resource-constrained applications. C still plays a critical role in 21st-century programming, remaining the core language for precision engineering, aviations, space research, and more. This book shows how C works with Unix, how to implement OO principles in C, and fully covers multi-processing. In Extreme C, Amini encourages you to think, question, apply, and experiment for yourself. The book is essential for anybody who wants to take their C to the next level.
Table of Contents (23 chapters)

Happens-before constraint

We established in the previous section that context switches are not predictable; there is uncertainty about the time at which they are likely to occur in our programs. Despite that, there is certainty about the instructions that are being executed concurrently.

Let's continue with a simple example. To start with, we're going to work on the basis that we've got a task like the one you see next in Code Box 13-1, which has five instructions. Note that these instructions are abstract, and they don't represent any real instructions like C or machine instructions:

Task P {
    1. num = 5
    2. num++
    3. num = num – 2
    4. x = 10
    5. num = num + x
}

Code Box 13-1: A simple task with 5 instructions

As you can see, the instructions are ordered, which means that they must be executed in that specified order in order to satisfy the purpose of the task. We are certain about this. In technical terms, we say that we have...