Category Archives: C/C++ Programming

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

Niall Cooling

Director at Feabhas Limited
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.

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

A convenient untruth

Glennan Carnie

Glennan Carnie

Technical Consultant at Feabhas Ltd
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.
Glennan Carnie

Latest posts by Glennan Carnie (see all)

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

Posted in C/C++ Programming | Tagged , , , | 9 Comments

Death and (virtual) destruction*

Glennan Carnie

Glennan Carnie

Technical Consultant at Feabhas Ltd
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.
Glennan Carnie

Latest posts by Glennan Carnie (see all)

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

Posted in C/C++ Programming, Design Issues | Tagged , , , , , , , , | 9 Comments

Getting your head around auto’s type-deduction rules

Glennan Carnie

Glennan Carnie

Technical Consultant at Feabhas Ltd
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.
Glennan Carnie

Latest posts by Glennan Carnie (see all)

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 […]

Posted in C/C++ Programming | Tagged , , , , , , , , , , | 1 Comment

Great Expectations

Glennan Carnie

Glennan Carnie

Technical Consultant at Feabhas Ltd
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.
Glennan Carnie

Latest posts by Glennan Carnie (see all)

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 […]

Posted in C/C++ Programming, Design Issues | Tagged , , , , , , , , | 2 Comments

The three ‘No’s of sequential consistency

Glennan Carnie

Glennan Carnie

Technical Consultant at Feabhas Ltd
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.
Glennan Carnie

Latest posts by Glennan Carnie (see all)

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

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

Memory consistency made simple(ish)

Glennan Carnie

Glennan Carnie

Technical Consultant at Feabhas Ltd
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.
Glennan Carnie

Latest posts by Glennan Carnie (see all)

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 […]

Posted in C/C++ Programming, Design Issues, General | Tagged , , | 1 Comment

Function Parameters and Arguments on 32-bit ARM

Niall Cooling

Director at Feabhas Limited
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.

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

Seeing stars. And dots. And arrows.

Glennan Carnie

Glennan Carnie

Technical Consultant at Feabhas Ltd
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.
Glennan Carnie

Latest posts by Glennan Carnie (see all)

This time I want to look at a seemingly trivial concept in C++ programming: accessing class members, either directly or via a pointer.  More than anything it’s an excuse to talk about two of C++’s more obscure operators – .* and

Posted in C/C++ Programming | Tagged , , , , , , , , , | 1 Comment

Becoming a Rule of Zero Hero

Glennan Carnie

Glennan Carnie

Technical Consultant at Feabhas Ltd
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.
Glennan Carnie

Latest posts by Glennan Carnie (see all)

“Do, or do not; there is no ‘try’.”

Previously, we’ve looked at The Rule of Zero which, in essence, says: avoid doing your own resource management; use a pre-defined resource-managing type instead.

This is an excellent guideline and can significantly improve the quality of your application code. However, there are some circumstances where you might not get exactly what you were expecting. It’s not that the code will fail; it just might not be as efficient as you thought.

Luckily, the solution is […]

Posted in C/C++ Programming | Tagged , , , , , , , , , , , | 7 Comments