how bad is it to use dynamic datastuctures on an embedded system?

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So in an embedded systems unit, that i'm taking at uni next year, we will learn that dynamic data structures are a bad thing to have in an embedded system program. but the lecture notes don't go into why.

Now i'm working on a moderate scale, embedded systems\ 'LURC' controller, mostly just takes advantages of the peripheral of the "Butterfly" demo board for the AVR169MEGA. produced 4 PWM signals to contol servo's and ESC. and also to provide an 9 seg LCD screen.

Now I can't think of anybetter way to store instructions as they are recieved vial USART serial, than a queue. esp for things where I'll need to wait until an unknown amount of data has been recieved: eg a string to display on the LCD screen.

so why don't you uses dynamic data structures on a microcontroller in a embedded systems? Is it just that you're on a heavily memory restricted enviroment, and have to be sure your mallocs are succeeding?

avr stack queue list
9 Answers

I do not think that utilizing dynamic allocation in embedded systems is a bad idea. I just want to say that there are some points you need to avoid.

  1. Be careful with your HEAP size. If you exceed the MAX_HEAP limit described in your linker file, a hardware exception might occur.
  2. Allocating an area after the system started up may cause delays in your time-dependent tasks. So, you better allocate the area you want during the initialization phase. That's not a rule, just a suggestion:)
  3. Think again if you can solve the problem you are facing without dynamic allocation.

Also, I think dynamic allocation is one of the superior features of programming languages. Thus, I can't think of designing an application that is well structured without it :)

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