Can Exception stack trace ever be null?

Question

I found out that if I am catching an Exception e, e.innerException could possibly be null.

Is it also possible that e.StackTrace could also be null in any possible circumstance in a catch block?

try {

}
catch(Exception e)
{
//can e.StackTrace be null here?
}

I would say yes: http://stackoverflow.com/questions/5620678/nullreferenceexception-no-stack-trace-where-to-start http://stackoverflow.com/questions/6783561/nullreferenceexception-with-no-stack-trace-when-hooking-setconsolectrlhandler — Aaron Palmer, Feb 10 '14 at 22:01

score 18 · Answer 1 · answered Feb 10 '14 at 21:56

18

Yes.

If you create a new Exception() and don't throw it, every property except Data and Message will be null.

answered Feb 10 '14 at 21:56

SLaks

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I think more importantly, if you do not code exceptions properly, [then all sorts of debug information may go missing](http://stackoverflow.com/questions/22623/throwing-exceptions-best-practices). – Erik Philips Feb 10 '14 at 21:57
1

What if it's in a catch block? – Henley Feb 10 '14 at 21:58
@Servy: Wrong. (try it) – SLaks Feb 10 '14 at 22:02
@HenleyChiu: It can be empty, but I don't think it can be null. – SLaks Feb 10 '14 at 22:02

score 4 · Answer 2 · answered Feb 10 '14 at 22:03

4

An example that proves the StackTrace can be null in a catch block is equally trivial to show:

public class DerpException : Exception
{
    public override string StackTrace
    {
        get { return null; }
    }
}

answered Feb 10 '14 at 22:03

Preston Guillot

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I'm actually shocked that `StackTrace` is virtual, simply because derived classes *shouldn't* be able to do something like this. – Servy Feb 10 '14 at 22:04
Looking in dotPeek, the property is actually defined in the `System.Runtime.InteropServices._Exception` interface, which explains why it's virtual in the base `System.Exception` class - the reasons for this interface are out of my reach as a lowly purveyor of purely managed code though. – Preston Guillot Feb 11 '14 at 01:04
1

The `Exception` class could still mark it as `sealed`, preventing *further* overrides of that property. – Servy Feb 11 '14 at 14:11
Sealing `Exception` would prevent *any* kind of more specific exception class from existing though. Inheriting the field from an interface doesn't force it to be implemented as `virtual` in the base `Exception` class either though, it just has to be `public`; I was brain dead at that point yesterday. – Preston Guillot Feb 11 '14 at 15:20
1

You can seal that property (or a method) without sealing the whole class. That's what I suggested. – Servy Feb 11 '14 at 15:21
1

I misread initially, but you don't even need to do that since methods aren't virtual by default in C#, you just need to *not* have the method be marked virtual, which is back to the original point. It seems like a deliberate design decision, and a really odd one. – Preston Guillot Feb 11 '14 at 15:37

score 0 · Answer 3 · answered Jun 05 '20 at 18:13

It's possible to get exception.StackTrace as a null, if you use [HandleProcessCorruptedStateExceptions] attribute for your function with try-catch, where you catch exception, and if exception is thrown from native code.

System.AccessViolationException exception type might have StackTrace as null.

Not sure if this has anything to do with Debug/Release build and/or generated pdb files. I've observes this kind of crash for Release build.

score 0 · Answer 4 · answered Feb 06 '22 at 22:55

I encountered a case where the exception had a Message, but the mere access of StackTrace threw an exception!

This worth repeating: Just accessing the StackTrace threw an exception, i.e. without even calling a method upon it (like ex.StackTrace.ToString()).

This happened when working with COM libraries.

Specifically, it happened when a .NET Framework dll referenced an interop dll. For some reason the clr couldn't find and load that interop dll, and the exception thrown was a normal System.IO.FileNotFoundException, which had a Message.

But, accessing its StackTrace itself threw an exception with the following stack trace:

System.Signature.GetSignature(Void* pCorSig, Int32 cCorSig, RuntimeFieldHandleInternal fieldHandle, IRuntimeMethodInfo methodHandle, RuntimeType declaringType)\r\n   at
System.Reflection.RuntimeMethodInfo.FetchNonReturnParameters()\r\n   at  
System.Reflection.RuntimeMethodInfo.GetParameters()\r\n   at   
System.Diagnostics.StackTrace.ToString(TraceFormat traceFormat)\r\n   at   
System.Environment.GetStackTrace(Exception e, Boolean needFileInfo)\r\n   at  
System.Exception.GetStackTrace(Boolean needFileInfo)\r\n   at  
System.Exception.get_StackTrace()

Can Exception stack trace ever be null?

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