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Brilliant exception handling I found in an app i had to work on (media.kbin.social)

submitted 1 year ago by [email protected] to c/[email protected]

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Brilliant exception handling I found in an app i had to work on

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[–] Shareiff 6 points 1 year ago (6 children)

Lol what’s wrong with this if the parent function catches it

[–] [email protected] 13 points 1 year ago (1 children)

If this is C# (and it looks like it is), this leads to you losing the original stack trace up until this point.

The correct way to do this in C# is to just throw; after you're done with whatever you wanted to do in the catch.

[–] jyte 4 points 1 year ago* (last edited 1 year ago) (1 children)

wait what ?

So you are saying that the following code will keep throwing e but if I used throw e; it would basically be the same except for the stack trace that would be missing the important root cause ?!

try {
} catch (WhateverException e) {
    // stuff, or nothing, or whatever
    throw; 
}

[–] [email protected] 4 points 1 year ago

Exactly. Aside from deleting your already built stack trace, as a bonus you'll get another stack trace building call, enjoy wasted CPU cycles.

[–] chillhelm 6 points 1 year ago (1 children)

Depending on the language it either does nothing and just adds code bloat or (and this would be much worse) it will catch any exception that can be implicitly cast to type Exception and throw it as type Exception. So the next higher scope would not be able to catch e.g. a RuntimeException or w.e. to handle appropriately. It could only catch a regular Exception even if the original error was a more detailed type.

[–] [email protected] 5 points 1 year ago (1 children)

It's C# so it's just rethrowing the original exception.

It might also be messing with the stack trace though which can be a bit frustrating for future debugging. But that's only a vague recollection of something I read in the past so I could be wrong

[–] Pieisawesome 1 points 1 year ago (1 children)

Throwing exceptions are very costly due to the stack trace, so building the stack trace twice will cause a big performance hit

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (1 children)

Correct me if I'm wrong, but this will actually cut the stack trace and then start another one from your try-catch block, which is an evil thing to do towards those who will actually read your stack traces. To preserve the stack trace you do throw;, not throw ex;, and I'm assuming IDE is underlining that statement exactly for this reason.

[–] Pieisawesome 1 points 1 year ago

Yes, hence why I mentioned it collects the stack trace twice.

It's more than just more difficult for debugging

[–] [email protected] 3 points 1 year ago (1 children)

The catch is useless if it's just throwing the exception anyway

[–] [email protected] 2 points 1 year ago

The catch is mandatory...

[–] [email protected] 3 points 1 year ago

You don't catch it if that's the case

[–] [email protected] 2 points 1 year ago

You could just not catch it and it'll get thrown up the stack anyway.

[–] [email protected] 1 points 1 year ago

Then the parent function would catch the original exception if it was never caught in the first place. All this does is bork the stacktrace.