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.

Thanks for the memory (allocator)

One of the design goals of Modern C++ is to find new – better, more effective – ways of doing things we could already do in C++.  Some might argue this is one of the more frustrating aspects of Modern C++ – if it works, don’t fix it (alternatively: why use lightbulbs when we have perfectly good candles?!)

This time we’ll look at a new aspect of Modern C++:  the Allocator model for dynamic containers.  This is currently experimental, but has […]

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A brief introduction to Concepts – Part 2

In part 1 of this article we looked at adding requirements to parameters in template code to improve the diagnostic ability of the compiler.  (I’d recommend reading this article first, if you haven’t already)

Previously, we looked at a simple example of adding a small number of requirements on a template parameter to introduce the syntax and semantics.  In reality, the constraints imposed on a template parameter could consist of any combination of

Type traits
Required type aliases
Required member attributes
Required member functions

Explicitly listing […]

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A brief introduction to Concepts – Part 1

Templates are an extremely powerful – and terrifying – element of C++ programs.  I say “terrifying” – not because templates are particularly hard to use (normally), or even particularly complex to write (normally) – but because when things go wrong the compiler’s output is a tsunami of techno-word-salad that can overwhelm even the experienced programmer.

The problem with generic code is that it isn’t completely generic.  That is, generic code cannot be expected to work on every possible type we could […]

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Technical debt

What is it & how does it affect software engineering management?
The ‘Golden Triangle’ of project management

The ‘golden triangle’ of project management uses the following constraints:

The rule is: you can pick any two of three; you can’t have them all.

When it comes to software development projects, it’s not uncommon to have a fixed time to market and budget, which means that, under pressure, the constraint that’s affected is quality.

Commonly, when the project management refers to ‘quality’ it implicitly means Intrinsic Quality.

Intrinsic […]

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Your handy cut-out-and-keep guide to std::forward and std::move

I love a good ‘quadrant’ diagram.  It brings me immense joy if I can encapsulate some wisdom, guideline or rule-of-thumb in a simple four-quadrant picture.

This time it’s the when-and-where of std::move and std::forward.  In my experience, when programmers are first introduced to move semantics, their biggest struggle is to know when (or when not) to apply std::move or std::forward.  Usually, it’s a case of “keep apply std::move until it compiles”.  I’ve been there myself.

To that end I’ve put together a […]

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Setting up Sublime Text to build your project

For many years embedded development was dominated by complex integrated development environments (IDEs) that hide away all the nasty, messy details of a typical embedded software project.

Recently, with the rapidly accelerating adoption of agile techniques in embedded systems, there has been a move away from integrated development environments towards smaller, simpler, individual tools.  Tools like CMake, Rake and SCons are used to manage build configurations.  Container facilities like Docker provide lightweight environments for build and test.  And developers are free […]

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“May Not Meet Developer Expectations” #77

Question:  Does the following compile?

int func()
{
  int (func);
  return

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Exceptional fun!

In this article I want to look at some applications for one of C++’s more obscure mechanisms, the function

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Making things do stuff – Part 9

As a final instalment in this series on hardware manipulation I thought I’d revisit read-only and write-only register types.

Using tag dispatch is not the only way to solve the read- or write-only Register problem.  For completeness let’s explore two other alternatives – SFINAE and constexpr if.

For these examples I’m going to use a simplified version of our Register class.  I’m ignoring the bit proxy class and using a reduced API.  Once understood, the techniques below can be applied to these […]

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Making things do stuff – Part 8

We’ve been using templates to provide a hardware register abstraction for use with hardware manipulation problems, typical of what you’d find in a deeply-embedded (“bare-metal”) system.

Previously, we looked at using trait classes to establish pointers and tag-dispatch to handle special-case registers, such as read-only or write-only register.

In this article we’re going to add some syntactic sugar to our Register class, to allow the developer to access individual bits in the register using array-index ([]) notation.  This will allow us to […]

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