Mawg Mawg - 29 days ago 22
C++ Question

Embedded C++ : to use STL or not?

I have always been an embedded software engineer, but usually at Layer 3 or 2 of the OSI stack. I am not really a hardware guy. I have generally always done telecoms products, usually hand/cell-phones, which generally means something like an ARM 7 processor.

Now I find myself in a more generic embedded world, in a small start-up, where I might move to "not so powerful" processors (there's the subjective bit) - I cannot predict which.

I have read quite a bit about debate about using STL in C++ in embedded systems and there is no clear cut answer. There are some small worries about portability, and a few about code size or run-time, but I have two major concerns:

1 - exception handling; I am still not sure whether to use it (see Embedded C++ : to use exceptions or not?)

2 - I strongly dislike dynamic memory allocation in embedded systems, because of the problems it can introduce. I generally have a buffer pool which is statically allocated at compile time and which serves up only fixed size buffers (if no buffers, system reset). The STL, of course, does a lot of dynamic allocation.

Now I have to make the decision whether to use or forego the STL - for the whole company, for ever (it's going into some very core s/w).

Which way do I jump? Super-safe & lose much of what constitutes C++ (imo, it's more than just the language definition) and maybe run into problems later or have to add lots of exception handling & maybe some other code now?

I am tempted to just go with Boost, but 1) I am not sure if it will port to every embedded processor I might want to use and 2) on their website, they say that they doesn't guarantee/recommend certain parts of it for embedded systems (especially FSMs, which seems weird). If I go for boost & we find a problem later ....

Answer

Super-safe & lose much of what constitutes C++ (imo, it's more than just the language definition) and maybe run into problems later or have to add lots of exception handling & maybe some other code now?

We have a similar debate in the game world and people come down on both sides. Regarding the quoted part, why would you be concerned about losing "much of what constitutes C++"? If it's not pragmatic, don't use it. It shouldn't matter if it's "C++" or not.

Run some tests. Can you get around STL's memory management in ways that satisfy you? If so, was it worth the effort? A lot of problems STL and boost are designed to solve just plain don't come up if you design to avoid haphazard dynamic memory allocation... does STL solve a specific problem you face?

Lots of people have tackled STL in tight environments and been happy with it. Lots of people just avoid it. Some people propose entirely new standards. I don't think there's one right answer.