alt Hacker NewsIn low-level systems software, which is a primary use case for C++, exceptions can introduce nasty edge cases that are difficult to detect and reason about. The benefits are too small to justify the costs to reliability, robustness, and maintainability.
Exceptions in high-level languages avoid many of these issues by virtue of being much further away from the metal. It is a mis-feature for a systems language. C++ was originally used for a lot of high-level application code where exceptions might make sense that you would never use C++ for today.
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> In low-level systems software, which is a primary use case for C++
I can assure you: Most C++ SW is not written for low-level.
> exceptions can introduce nasty edge cases that are difficult to detect and reason about.
That's true, except for languages that ensure you can't simply forget that something deep down the stack can throw an exception.
BTW, I'm not saying C++'s exceptions are in any way good. My point is that exceptions are bad in C++, and not necessarily bad in general.
If you forget to handle a C++ exception you get a clean crash. If you forget to handle a C error return you get undefined behavior and probably an exploit.
Exceptions are more robust, not less.
C++ exceptions are fast for happy path and ABI locked for sad path. They could be much faster than they are currently. Khalil Estell did a few talks/bunch of work on the topic and saw great improvements. https://youtu.be/LorcxyJ9zr4
> "In low-level systems software, which is a primary use case for C++, exceptions can introduce nasty edge cases that are difficult to detect and reason about. The benefits are too small to justify the costs to reliability, robustness, and maintainability."
Interestingly, Microsoft C / C++ compiler does support structured exception handling (SEH). It's used even in NT kernel and drivers. I'm not saying it's the same thing as C++ exceptions, since it's designed primarily for handling hardware faults and is simplified, but still shares some core principles (guarded region, stack unwinding, etc). So a limited version of exception handling can work fine even in a thing like an OS kernel.
Exceptions are actually a form of code compression. Past some break even point they are a net benefit, even in embedded codebases. They're "bad" because the C++ implementation is garbage but it turns out it's possible to hack it into a much better shape:
> In low-level systems software, which is a primary use case for C++
I don't this this is true. There is A LOT of C++ for GUI applications, video games, all kind of utilities, scientific computing and others. In fact, I find that the transition to "modern" alternatives from native GUI toolkits in C/C++ has led to a regression in UI performance in general. Desktop programs performed better 20 years ago when everything was written in Win32, Qt, GTK and others and people did not rely on bloated Web toolkits for desktop development. Even today you can really feel how much more snappy and robust "old school" programs are relative to Electron and whatnot.