[Const-me]

> So you cant use the STL.

std::array is in there since C++ 11 and it doesn’t use heap.

And/or you can use STL with custom allocators that work without heap. We did something similar developing for Nintendo Wii console. There was a heap but we didn’t want to use it to avoid memory fragmentation. AFAIR we used two arenas (essentially stacks), one very small for temporary data cleaned up at the start of each frame, and a large one cleaned up when a level is unloaded.

However, I don’t have hands on experience developing firmware for medical devices, so I’m not sure it’ll work for them.

[AnimalMuppet]

The problem for medical devices isn't so much whether custom allocators will work. The problem is whether the FDA will freak out because you're not following industry-best-practice coding guidelines.

[ska]

That's really not how it works. The FDA is fundamentally concerned about two things, safety and efficacy. You need a plan to demonstrate the latter, and you need your quality system, SDP, etc. to demonstrate how you approach the former. This is about good engineering practices, not particular implementation techniques.

So you can do things many different ways. If you do say "we do this like X, which is industry standard, just like T, U, and V do" it's a simpler argument than "we do this like Y. Lots of people do X, but here is how we have demonstrated Y is better for us...". But this can be fine too, just possibly more work.

Also worth noting (a) there is no industry-wide best practices agreement (b) there is no FDA wide agreement on what should be done (different device types are reviewed by different panels (c) the FDA doesn't understand software development deeply across it's panels, but it is catching up.

[AnimalMuppet]

Sure, that's all true. I'm looking at the "simpler argument" part.

It's especially true if you're saying "This new device is just like our previous device, with these few small changes". (I forget what that's called, but you can do a lot less paperwork if that's true.) But if you start doing memory allocations where you never did before, they're probably going to want to apply higher scrutiny to your entire software. That's... painful.

[ska]

You are possibly thinking about note-to-file (which isn’t quite the process any more, but similar)

But it is worth pointing out, FDA (or other national body) isn’t doing code reviews. They are mostly interested in process , and how you follow it. The place where this really interacts s is hazard analysis, and then it’s just up to you to demonstrate your checks and balances.

[gowld]

Arenas/Pools/Planks have been industry best-practice for my entire career.

[gpderetta]

Also, STL is data structures + algorithms. Even if you can't use the datastructures out of the box you might be able to use the algos. Boost.Intrusive provides STL compatibe datastructures with full control of allocation (and more).