Why Function Pointers are Awesome

In this 2022 Embedded Online Conference Microtalk, Jacob Beningo discusses the use cases for function pointers in embedded software.
This video looks at the C programming language function pointers, and how they can be leveraged for use cases such as:
- task scheduling
- command processing
- state machines
- interrupt vector tables
Developers often get confused that function pointers shouldn't be used in embedded systems because of MISRA C: 1998 Rule 104. As you'll see in this video, there are safe methods for using function pointers.
(The Embedded Online Conference will take place April 25 - 29th, 2022. If you are interested in participating, you can register with the code BENINGO to get at least a $100 discount).

[@ralflici986]

Very interesting talk, thank you!

[@CuriousCyclist]

Really good video! Thanks for taking the time to make it.

[@LomasSubedi]

Thank you Jacob, your presence in here and on different blog article is helping so much to learn and understand.

[@beningoembedded]

Happy to hear that!

[@grimvian]

The use cases gives me inspiration to enhance my C code, so a big thank you from me.

[@bahtiyar.bayram]

Great content!

[@btoven66]

Great to see you again!!!

[@beningoembedded]

Thanks Peter! I'm planning to post a lot more this year so stay tuned!

[@deltakid0]

Could you please explain how the ATTiny85 bootloader works? It's a very basic MCU. Thank you.

[@ThePing98]

Great video thank u

[@beningoembedded]

Glad you enjoyed it

[@waynerifish]

Regarding "Make sure function pointers are NOT stored in RAM"... when I register a callback function, isn't that callback function pointer stored in RAM somewhere (e.g., UART0_ISR->function), even if it's done in pre-compiled or auto-generated code?

[@shahfenil08]

Interestingly, I violated the rule that said it should be constant and my code was crashing because it was pointing to the 0x0. As I was debugging the issue, I found out another bug index out range. So one bug exposed another nasty bug. Note that, before implementing function pointer other bug was still there but I couldn't find out because my program haven't crashed or going into hard fault. :D

[@boudewijndijkstra82]

Another problem is that calculating the maximum stack usage becomes non-trivial. For each function pointer invocation it has to be clear which functions can potentially be called.

[@beningoembedded]

Absolutely! Thanks for the comment and observation!

[@Bob-zg2zf]

I just bought your book today.❤

[@beningoembedded]

Excellent! I hope you enjoy it!

[@Bob-zg2zf]

@@beningoembedded I ordered it but I have not received it. I hope I will indeed enjoy it as much as I enjoyed your videos. The thing is, my expertise level is not that advanced. I am afraid I won't understand all or most of your book's contents. But I like your video contents and style and background.

[@Bob-zg2zf]

@@beningoembedded Do you mind if I ask you a simple question? I have read your article, where you mentioned that we are supposed to "write rock-solid embedded software". But I can only design and solder an STM32 board with HCD1080, using someone's Keil project code that I downloaded from the Internet. So, how do I write my own entire project/code? How do I improve myself from using others' code to "write my own rock-solid embedded software"? The architecture seems so difficult to master to write from scratch or modify here and there....

[@hsaidinsan6345]

Do they affect the real time performance?

[@beningoembedded]

Function pointers will not have a negative impact on the real-time performance. They can improve readability, scalability, and reusability though. They can also decrease maintenance too. If you were to look at what a function call really is, it's just a pointer to the functions code anyway!