C++ On Embedded Systems

Overview

The document “Technical Performance on C++ Performance” is a good read if you are really interested in the advantages/disadvantages of using C++ on an embedded platform.

The Embedded C++ Homepage is sort of a hub for embedded C++ programming. They define a sub-set of the full C++ language for use on embedded devices such as microcontrollers.

Performance Concerns

One fear about using C++ on an embedded system is a decrease in performance (in terms of memory and processing speed). As with most complex issues, the answer really is, “it depends”.

I believe you can carefully select a subset of the C++ language which provides most of the benefits of OO-based design, but does not incur any performance hits for the target system.

C++ Features That Should Be Used

• Classes (pretty much no overhead)
• Templates (no overhead, can be thought of as a more powerful version of a macro). However, incorrect/careless use of template can cause a huge increase in code size.
• Function overloading
• Typesafe enums (i.e. enum class), typesafe typedefs
• Operator overloading (when done sensibly!)
• References (they are just safer pointers!)
• Namespaces (no overhead)
• Inhertiance
• auto

C++ Features That Could Be Used, But Only After Careful Consideration

• Virtual Methods -
• RTTI -
• STL
• Boost

C++ Standrad Libraries For Embedded Devices

uClibc++ is a C++ standard library designed specifically for microcontrollers. It even has exception support!

Check out The Standard Template Library (STL) For AVR With C++ Streams if you want to get a library for using things like string and iostream with AVR microcontrollers.