Code that intentionally fails

Question

Is it bad style and/or bad for performance to write code that you know might fail and ignore the exception? For example (in C#):

long l = 1;
try {
  l = (long)castObject;
} catch(InvalidCastException e) { }

In this scenario, the programmer doesn't particularly care whether or not an InvalidCastException is thrown.

I generally try to avoid swallowing exceptions as that's a bad practice to get into, even if it may not seem to be an issue in a particular instance. — Tim, Sep 19 '14 at 02:37
Why not `long? v = castObject as long?; if (v.HasValue) l = v.Value;`? — Mephy, Sep 19 '14 at 02:37
@Tim you can't `as` to a value type like `long`, needs `long?` or `Nullable` instead. — Mephy, Sep 19 '14 at 02:38
Side note: likely the problem is not in that piece of code , but rather in other code that uses non-generic collections or some other code that ignores type of objects... (in any case if you need to ignore particular exception you should catch just that exception) — Alexei Levenkov, Sep 19 '14 at 02:46
@Mephy thanks for the info, I didn't know about using `?` for nullable types like that. @SLaks very good to know, thanks. — drew.cuthbert, Sep 19 '14 at 02:47

score 6 · Accepted Answer · answered Sep 19 '14 at 02:38

6

Don't do that.

Exceptions incur a substantial performance hit.
It will annoy developers who run with Break On Exceptions turned on.
(which you should do to catch hidden bugs)
It makes the intent less clear. (why might it not be a long?)

answered Sep 19 '14 at 02:38

SLaks

3

In addition to the above, the `catch` can catch stuff that you probably don't want to hide, such as `OutOfMemoryException`, `Exception` and `StackOverflowException`. – Sam Sep 19 '14 at 02:45
2

@Sam no, that's not correct as StackOverflowException cannot be caught. See http://msdn.microsoft.com/en-us/library/system.stackoverflowexception(v=vs.110).aspx – Brian Rasmussen Sep 19 '14 at 02:46
@BrianRasmussen: A cast operation can't throw that anyway. (although a property setter could) – SLaks Sep 19 '14 at 02:52
1

@SLaks true, it was more a general comment about that particular exception. – Brian Rasmussen Sep 19 '14 at 04:05
Regarding your point about the `try`-`catch` making the intent less clear, you could just encapsulate the code in a descriptively-named method or use a comment, so I don't think that aspect is necessarily a problem, especially if `try`-`catch` is the only way to do something due to the API you're working with. – Sam Sep 19 '14 at 04:42

1 Answers1