Category Archives: Design Issues

The Rule of Zero

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.

Latest posts by Glennan Carnie (see all)

In a previous article – ”The Rule of the Big Four (and a half)” we looked at resource management policies in C++.

Resource management is the general term for using the mechanisms in C++ to ensure that resources – files, dynamic memory, sockets, mutexes, etc – have their lifetimes automatically controlled so as to prevent resource leaks, deadlocks, etc. C++ refers to these mechanisms as RAII/RDID ( “Resource Acquisition Is Initialisation / Resource Destruction is Deletion”)

In this article we’ll have a […]

Posted in C/C++ Programming, Design Issues | Tagged , , , , , , , | 17 Comments

Software Duct Tape – Binding the C++ Universe Together

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.

Latest posts by Glennan Carnie (see all)

One of the cornerstones of object-oriented design is the concept of objects interacting by sending messages to form mechanisms – units of higher-order (or ‘emergent’) behaviour.

In order to send a message (in this case, invoke a member function) an object must have a ‘link’ to the target object. That link is formed by building in an association between the two classes as part of the type’s definition.

In this article we look at building associations between classes and forming run-time links […]

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The hokey-cokey* of function calls

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.

Latest posts by Glennan Carnie (see all)

Functions are the lifeblood of a C program. The program flow is altered by passing parameters to functions, which are then manipulated. Conceptually function parameters are defined as being either:

Inputs (Read-only) – client-supplied objects manipulated within the function only
Outputs (Write-only) – objects generated by the function for use by the client.
Input-Outputs (Read-Write) – client objects that can be manipulated by the function.

Defining the use of a parameter gives vital information not only to the implementer, but (perhaps more importantly) to […]

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Casting – what could possibly go wrong?

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.

Latest posts by Glennan Carnie (see all)

Type casting in C++ is a form of what is known in computer science as type punning – that is, circumventing the type system of a programming language.

C++ inherits its conversion and casting mechanism from C, but supplements it (although sensibly we should say, replaces it) with four, more explicit cast operations:

static_cast
reinterpret_cast
const_cast
dynamic_cast

In C and C++ – and particularly in embedded systems – casting is a necessary evil; so much so that many programmers just accept it […]

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Debunking priority

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.

Latest posts by Glennan Carnie (see all)

Before I start, a disclaimer:

For the purposes of this article I’m limiting the discussion to even-driven systems on priority-based, pre-emptive operating systems, on single processors.

I’m using the word task to mean ‘unit of execution’ or ‘unit of schedulability’, in preference to thread or process. I’m ignoring the different OS memory models.

There seems to be a fair amount of misunderstanding about the concept of priority in concurrent programming:

Priority means one task is more ’important’ than another.
Priority allows one task to […]

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Style vs. Substance in C programming

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.

Latest posts by Niall Cooling (see all)

In an email from UBM Tech this week there was a link to an article titled “A Simple Style for C Programming by Mansi Research“. It was actually authored back on May 2010 by Meetul Kinariwala but appeared this week under the what’s hot section, so I thought I’d take a look [advice to the reader; don’t bother].

The problem with guides like this is that style is a very subjective area (as any parent will tell you how their kids […]

Posted in C/C++ Programming, Design Issues, General | Tagged , , | 7 Comments

Sailing the Seven C’s of design*

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.

Latest posts by Glennan Carnie (see all)

I’m always looking for nice little mnemonics to help out remember the important concepts in design.  Here’s one for model-driven development I call the “Seven C’s”.  It basically enumerates the seven stages a design goes through, from initial idea to code.

CONCEPT The Concept phase is about understanding the problem.  In other words: requirements analysis.  When you’re in Concept mode your main focus is on validation – am I solving the right problem for my […]

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Capturing the Stripe-d Flag 2.0 – The After Party

Following on from our previous article looking at Stripe’s Capture the Flag 2.0 challenge, Team Feabhas cracked the last of the levels and its members should hopefully be receiving their complementary t-shirts soon.

It has proven to be a popular article with lots of people coming to the blog for solutions and walk-through, and now that the competition has finished we have decided to share the way we approached each of these levels, their solution and the way in which the […]

Posted in Design Issues, General, Testing | Tagged , , | 2 Comments

Can existing embedded applications benefit from Multicore Technology?

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.

Latest posts by Niall Cooling (see all)

It feels that not a day goes by without a new announcement regarding a major development in multicore technology. With so much press surrounding multicore, you have to ask the question “Is it for me?” i.e. can I utilise multicore technology in my embedded application?

However, from a software developer’s perspective, all the code examples seem to demonstrate the (same) massive performance improvements to “rendering fractals” or “ray tracing programs”. The examples always refer to Amdahl’s Law, showing […]

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The Five Orders of Ignorance

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.

Latest posts by Glennan Carnie (see all)

It’s not often you read a paper that has something unique and fresh to say about a topic, and expresses it in a clear and concise way.

Somehow, Phillip Armour’s The Five Orders of Ignorance had eluded me, until I found it referenced in another paper.

It really is an interesting point of view on software development.  You can read the paper here.

Armour’s central tenet is software is a mechanism for capturing knowledge. That is, (correct) software is the result of having […]

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