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Comment by whatshisface | Hacker News Reader

When something happens that violates your assumptions about your own program's behavior, throwing it into a state where it doesn't know what happens next. Kind of like a panic.

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This would mean that attempting to open a file that doesn't exist shouldn't throw an exception. But that is exactly what it does in the standard libraries of many languages with exceptions.

Not in C++ I believe ?

The C++ standard IO library doesn't enable exceptions by default, but IIRC that's just a relic of the fact that it dates back to when C++ didn't have exceptions.

It's library dependent. iostreams (part of C++ std lib) doesn't throw exceptions by default but I believe it can be configured to throw if you want.

https://en.cppreference.com/w/cpp/io/basic_ios/exceptions

Damn, in all those years I've absolutely never come across this, thanks

That is manually throwing an exception if the file doesn't exist.

C++ stdlib does not throw an exception if a file does not exist. I agree with this philosophy because files not existing isn't an exceptional case.

It should be up to the application to throw or not, not a library. I write a system service. If it can't find the configuration file, it can't continue, so it throws an exception. If it can't open a file that contains state from a previous run (maybe because it's the first time it's running) that's fine, the program can run without it and thus, no exception.

So, CPU exceptions such as a "page not present" TLB fault should not be used to implement virtual memory.

A "page not present" fault is actually a great example of a resumable condition, which is not quite the same as an exception in the C++ sense.

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