Tag Archives: C Declarations

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

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The hokey-cokey* of function calls

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)

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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Native C/C++ Application development for the mbed using CMSIS-DAP

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)

If you have been following the Feabhas blog for some time, you may remember that in April of last year I posted about my experiences of using the MQTT protocol. The demonstration code was ran the ARM Cortex-M3 based mbed platform.

For those that are not familiar with the mbed, it is an “Arduino-like” development platform for small microcontroller embedded systems. The variant I’m using is built using an NXP LPC1768 Cortex-M3 device, which offers a plethora of connection options, ranging […]

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Setting up the Cortex-M3/4 (ARMv7-M) Memory Protection Unit (MPU)

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)

An optional part of the ARMv7-M architecture is the support of a Memory Protection Unit (MPU). This is a fairly simplistic device (compared to a fully blow Memory Management Unit (MMU) as found on the Cortex-A family), but if available can be programmed to help capture illegal or dangerous memory accesses.
When first looking at programming the MPU it may seem rather daunting, but in reality it is very straightforward. The added benefit of the ARMv7-M family is the well-defined memory […]

Posted in ARM, C/C++ Programming, CMSIS, Cortex, Testing | Tagged , , , | 3 Comments

Weak linkage 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)

When linking C programs there are (in general) only a couple of errors you’re likely to see. If, for example, you have two functions in different files, both with external linkage, then the files will compile okay, but when you link you’ll likely see an error along these lines:

linking…
weak_linkage.axf: Error: L6200E: Symbol foo multiply defined (by foo.o and foo2.o).
Target not created

Most of the time this makes sense and is as expected; however there is a particular instance where it gets in the […]

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The C build process

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 this article we look at the C build process – that is, how we get from C source files to executable code, programmed on the target.  It wasn’t so long ago this was common knowledge (the halcyon days of the hand-crafted make file!) but modern IDEs are making this knowledge ever-more arcane.

Compilation

The first stage of the build process is compilation.

The compiler is responsible for allocating memory for definitions (static and automatic) and generating opcodes from program statements. A relocatable […]

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enum ; past, present and future

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)

The enumerated type (enum) is probably one of the simplest and most underused  features of the C and C++ which can make code safer and more readable without compromising performance.

In this posting we shall look at the basic enum from C, how C++ improved on C’s enum, and how C++0X will make them a first class type.

Often I see headers filled with lists of #defines where an enum would be a much better choice. Here is a classic example:

/* adc.h […]

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Declarations and Definitions in C

Please Note: This post is focusing on pre-C99. The reason being is that it is aimed at the embedded C programmer who tends to be working with pre-C99 based cross-compilers. Also I have split it into two as it became my larger, due to feedback, than first anticipated.

On the surface declarations and definitions in C are pretty straight-forward; but once we start introducing the concepts of scope, storage-duration, linkage and namespace life is not so simple.

Program […]

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Unscrambling C Declarations

Note: Based on some feedback I should clarify that this does not cover C99 syntax

Even though the C programming language has been around since the late 1960’s, many programmers still have trouble understanding how C declarations are formed. This is not unsurprising due to the complexity that can arise when mixing pointer, array and function-pointer declarations.
In this posting we shall look at some complex declarations to try and understand them by considering how they are formed. The intent is […]

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