This article is intended for programmers with some experience in embedded device programming who want to improve the quality of their code. What we cover today is the programming practice of implementing a function in such a way that there is only one place in the code to return value and also exit that routine, and usually it is at the and of the function block. This is called a single point of exit. There is a strong belief among experienced developers, confirmed by some standards such as MISRA C, that this approach is much better than having multiple exit points. To answer the question of whether a single exit point is really better than multiple exit points, let’s talk a bit about the pros and cons of each solution and then draw some conclusions.
In the screenshot below you can see two snippets of code. The one on the left shows multiple exit points, and the one on the right does the same but has only one exit point.
Single point of exit pros and cons
- First of all, a single return statement at the end of a function makes in easier to follow and understand. Readers can focus on the logic of the function without being distracted by multiple exit points scattered throughout.
- Second, and most importantly when using dynamic allocation or working on file streams, a single exit point ensures that all cleanup code (e.g. free(), fclose()) is centralized and executed before the function exits, preventing resource leakage. In other words, the ability to exit before deallocation is not possible
- Debugging is easier when there’s only one exit point to inspect, since you know where to set a breakpoint to track the function’s exit.
- When error-handling logic is consolidated near the end of the function, it’s easier to ensure that all error conditions are handled consistently.
- The only drawback I can think of right now is that the code is a bit bigger. For example, you have to introduce some variables to store the value to be returned at the end, or use some other mechanism like a „go to” statement to avoid doing unnecessary checks before exiting the function. Also, in general, using single exit points can take more time because you have to think about how to avoid an immediate exit, which is very often the natural solution.
Are there any benefits to using multiple exit points?
- Yes, there are some. One of them is something already mentioned. In rare cases, avoiding a single exit point can slightly improve performance (e.g., skipping unnecessary checks).
- Using multiple exit points is more natural and usually faster to implement. Writing code that avoids immediate exits usually requires more thought
- In cases where the code is very simple, using a single exit point usually looks like „over-engineering”.
The final verdict
As you have probably noticed, there are many advantages to using a single exit point, and there are no serious drawbacks to this solution. We can’t say the same for multiple exit points, especially if the function is large and involves dynamic memory allocation. Exiting too early can cause serious problems. However, there are some situations where there is not much difference, and a single exit point is more natural. These situations usually arise when writing simple „if else” logic, so always balance readability and practicality to decide whether a single exit point makes sense for a particular function, but in general this is the recommended solution, especially when:
- you are writing the code that manages resources like memory, files, or sockets.
- you are implementing complex logic with multiple branches.
- consistency and maintainability are more important than brevity.
Usefull links: