Author Archives: Glennan Carnie

About Glennan Carnie

Glennan is an embedded systems and software engineer with over 20 years experience, mostly in high-integrity systems for the defence and aerospace industry. He specialises in C++, UML, software modelling, Systems Engineering and process development.

Making things do stuff – Part 4

Posted on May 4, 2017 by Glennan Carnie

In the last article we explored the design of a class to encapsulate a physical hardware device.  In that article I deliberately ignored how the class would actually interact with the hardware.

In this article we explore the options available to us for accessing hardware and the consequences of those

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Making things do stuff – Part 3

Posted on April 20, 2017 by Glennan Carnie

Previously, we’ve looked at the basics of hardware manipulation in C++ and applied that to a simple GPIO implementation.

In this article we’re going to have a look at encapsulating our code in a class and look at some of the design choices we have to make.

If you’re not familiar with hardware manipulation in C++ I’d highly recommend reading the previous articles in this series before continuing.

Even if you’re familiar with the concepts of hardware manipulation, if you haven’t read the […]

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Making things do stuff – Part 2

Posted on April 6, 2017 by Glennan Carnie

Last time we looked at the basics of hardware manipulation in C++.   This time we’ll apply this to some real hardware and have a look at the code

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Making things do stuff – Part 1

Posted on March 23, 2017 by Glennan Carnie

C has long been the language of choice for smaller, microcontroller-based embedded systems; particularly for close-to-the-metal hardware manipulation.

C++ was originally conceived with a bias towards systems programming; performance and efficiency being key design highlights.  Traditionally, many of the advancements in compiler technology, optimisation, etc., had centred around generating code for PC-like platforms (Linux, Windows, etc).  In the last few years C++ compiler support for microcontroller targets has advanced dramatically, to the point where Modern C++ is a increasingly attractive language […]

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A convenient untruth

Posted on December 22, 2016 by Glennan Carnie

Array notation in C is a lie!

Sorry, dear reader*, but I cannot participate in this conspiracy any longer.  You have been lied to, manipulated and coerced into thinking arrays are a construct of the C language.  I feel it is my solemn duty to blow the whistle on this charade and expose the dirty secrets of C’s so-called arrays.

(* It is statistically possible that more than one person might read this, of

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Death and (virtual) destruction*

Posted on December 8, 2016 by Glennan Carnie

This time, we’ll have a more detailed look at one of those everybody-knows-that elements of C++ – virtual destructors.

More specifically, I want to reinforce under what circumstances you should make your destructor virtual; and when you don’t need to (despite what your compiler might say)

(*there’s no

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Getting your head around auto’s type-deduction rules

Posted on November 3, 2016 by Glennan Carnie

Automatic type-deduction is perhaps one of the more divisive features of Modern C++.  At its core it’s a straightforward concept:  let the compiler deduce the type of an object from its initialiser.   Used in the right way this can improve the readability and maintainability of your code.

However, because auto is based on template type-deduction rules there are some subtleties that can catch the unwary programmer.

In this article we’ll have a look at auto in the context of the template type-deduction […]

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Great Expectations

Posted on September 8, 2016 by Glennan Carnie

Previously, we’ve looked at the basic concepts of function parameter passing, and we’ve looked at the mechanics of how parameters are passed at the Application Binary Interface (ABI) level.

Far too often we focus on the mechanisms and efficiency of parameter passing, with the goal: if it’s efficient then it’s good; that’s all there is to it.  In this article I want to move past simple mechanics and start to explore function parameter design intent – that is, what can I […]

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The three ‘No’s of sequential consistency

Posted on August 11, 2016 by Glennan Carnie

In the previous article we looked at the memory consistency problem that occurs when writing multi-threaded code for modern multi-processor systems.

In this article is we’ll have a look at how we can solve the sequential consistency problem and restore some sanity to our programming

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Memory consistency made simple(ish)

Posted on July 28, 2016 by Glennan Carnie

The C++11 memory consistency model is probably one of the most significant aspects of Modern C++; and yet probably one of the least well-understood.  I think the reason is simple:  it’s really difficult to understand what the problem actually is.

The memory consistency problem is a concurrency problem.  That is, it’s a problem that occurs when we start writing multi-threaded code.  More specifically, it’s a parallelism problem – the real subtleties occur when you have two or more processors executing code.

In the first […]

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