Embedded C++ : to use STL or not?

Question

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 product

Answer 1

On our embedded scanner project we were developing a board with ARM7 CPU and STL didn't bring any issue. Surely the project details are important since dynamic memory allocation may not be an issue for many available boards today and type of projects.

Answer 2

I work on real-time embedded systems every day. Of course, my definition of embedded system may be different than yours. But we make full use of the STL and exceptions and do not experience any unmanageable problems. We also make use of dynamic memory (at a very high rate; allocating lots of packets per second, etc.) and have not yet needed to resort to any custom allocators or memory pools. We have even used C++ in interrupt handlers. We don't use boost, but only because a certain government agency won't let us.

It is our experience you can indeed use many modern C++ features in an embedded environment as long as you use your head and conduct your own benchmarks. I highly recommend you make use of Scott Meyer's Effective C++ 3rd edition as well as Sutter and Alexandrescu's C++ Coding Standards to assist you in using C++ with a sane programming style.

Edit: After getting an upvote on this 2 years later, let me post an update. We are much farther along in our development and we have finally hit spots in our code where the standard library containers are too slow under high performance conditions. Here we did in fact resort to custom algorithms, memory pools, and simplified containers. That is the beauty of C++ though, you can use the standard library and get all the good things it provides for 90% of your use cases. You don't throw it all out when you meet problems, you just hand-optimize the trouble spots.

Answer 3

Let me start out by saying I haven't done embedded work for a few years, and never in C++, so my advice is worth every penny you're paying for it...

The templates utilized by STL are never going to generate code you wouldn't need to generate yourself, so I wouldn't worry about code bloat.

The STL doesn't throw exceptions on its own, so that shouldn't be a concern. If your classes don't throw, you should be safe. Divide your object initialization into two parts, let the constructor create a bare bones object and then do any initialization that could fail in a member function that returns an error code.

I think all of the container classes will let you define your own allocation function, so if you want to allocate from a pool you can make it happen.

Answer 4

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.

Answer 5

1. for memory management, you can implement your own allocator, which request memory from the pool. And all STL container have a template for the allocator.

2. for exception, STL doesn't throw many exceptions, in generally, the most common are: out of memory, in your case, the system should reset, so you can do reset in the allocator. others are such as out of range, you can avoid it by the user.

3. so, i think you can use STL in embedded system :)