Author Archives: Niall Cooling

About Niall Cooling

Co-Founder and Director of Feabhas since 1995.
Niall has been designing and programming embedded systems for over 30 years. He has worked in different sectors, including aerospace, telecomms, government and banking.
His current interest lie in IoT Security and Agile for Embedded Systems.

An Introduction to Docker for Embedded Developers – Part 4 Reducing Docker Image Size

In Part 3  we managed to build a Docker image containing the tools required to compile and link C/C++ code destined for our embedded Arm target system. However, we’ve paid little attention to the size of the image. Doing a quick Docker image listing we can see its grown to a whopping 2.14GB:

$ docker image ls
REPOSITORY TAG IMAGE ID […]

Posted in Agile, ARM, C/C++ Programming, Cortex, Testing | Tagged , , , | Leave a comment

An Introduction to Docker for Embedded Developers – Part 3 Cross-Compiling for Cortex-M

In the previous posting we looked at defining a custom Dockerfile where we can add specific tools (and their dependencies). From that we created a Docker image and this allowed us to build C/C++ code in a Docker container, ensuring a consistent build environment.

So far we have to build all our code using the native GCC toolchain which is part of the base Docker image (gcc:7.2). However, I want to be able to build an image I can download and run […]

Posted in Agile, ARM, C/C++ Programming, Cortex, Testing | Tagged , , | Leave a comment

An Introduction to Docker for Embedded Developers – Part 2 Building Images

In the initial post, we covered the basics of getting Docker setup and using an official base image for compilation.
But let’s suppose the base image doesn’t include all the facilities our company uses for development. For example, we have migrated from make files to CMake, but more lately we have taken to using the python-based Scons build system for C/C++ projects.
The official gcc base image supports make but not Scons or CMake. As before, we can search for a Scons docker […]

Posted in Agile, General | Tagged , | 1 Comment

An Introduction to Docker for Embedded Developers – Part 1 Getting Started

Docker is a relatively new technology, only appearing just over four years ago. The core building blocks have always been part of Unix; but the significant support, Linux containers (LCX), first appeared back in 2008.

Initially Docker was only supported on Linux, but more recently native support for OSX (my development OS of choice) and Windows (albeit Windows 10 Pro) suddenly opens up some interesting workflow choices.

The “What”

So, first, what is Docker? I’m always trying to find the right words here […]

Posted in Agile, Design Issues, Testing | Leave a comment

‘Abusing’ the C switch statement – beauty is in the eye of the beholder

The C Language

Before we start, let’s get something straight; for over 30 years now I have had a love-hate relationship with the C programming language. The ‘engineer’ in me[1] sometimes just cannot believe we are still using C as the dominant embedded programming languages after all these years, and yet, I also see the simplicity and elegance the C code can bring. After all it’s just a tool, and even a good tool in the wrong hands; well we have plenty […]

Posted in C/C++ Programming | Tagged , , | 29 Comments

Function Parameters and Arguments on 32-bit ARM

Function call basics

When teaching classes about embedded C  or embedded C++ programming, one of the topics we always address is “Where does the memory come from for function arguments?“

Take the following simple C function:

void test_function(int a, int b, int c, int d);

when we invoke the function, where are the function arguments stored?

int main(void)
{
  //…
  test_function(1,2,3,4);
  //…
}

Unsurprisingly, the most common answer after “I don’t know” is “the stack“; and of course if you were compiling for x86 this would […]

Posted in ARM, C/C++ Programming, Cortex | Tagged , , | 5 Comments

My Top 5 Podcasts

For the final blog post of the year I’ve decided to do something a little different; I hope that’s okay?

Due to the nature of the job, the technical team at Feabhas spend a lot of time travelling. This means many an hour spent in the car driving to and from client sites; often involving navigating the wonderful M25 London orbital [car park!]. We all while away this time in different ways, some prefer music, others radio (which, being in the […]

Posted in General | Tagged | Leave a comment

Vulnerabilities in C : When integers go bad!

Insecure C?

We are at the dawn of a new era of connected embedded devices, broadly being marketed as the “Internet of Things” (IoT). The majority of these systems are likely to be programmed using C/C++. To date, much of the embedded world has been connected to propriety networks, however with the gold rush in to IoT we are not going to be able to rely on “Security through Obscurity“. This is the first in a series of articles looking […]

Posted in C/C++ Programming | Tagged | 2 Comments

goto fail and embedded C Compilers

I can’t imagine anyone reading this posting hasn’t already read about the Apple “goto fail” bug in SSL. My reaction was one of incredulity; I really couldn’t believe this code could have got into the wild on so many levels.

First we’ve got to consider the testing (or lack thereof) for this codebase. The side effect of the bug was that all SSL certificates passed, even malformed ones. This implies positive testing (i.e. we can demonstrate it works), but no negative testing […]

Posted in ARM, C/C++ Programming, Industry Analysis, Testing | Tagged , , , , , | 5 Comments

The Top 5 Things I’ve Learnt about Git

During the last couple of years, internally we’ve moved over to using Git as our Revision Control System (RCS). It’s been an interesting exercise, especially where, like me, you’ve come from a traditional model (such as subversion or even back to good old SCCS). I’m sure you’ve all got your own “top 5” and I don’t necessarily expect you to agree with me, but here’s my key learning points:

#1 “Branch always, branch often”
At the outset this was […]

Posted in General | Tagged , , , | 1 Comment