Empty catch

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DaTurk - 21 May 2007 18:55 GMT

What's the CLI equivalent of the empty catch?

i.e.
try{}
catch
{}

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William DePalo [MVP VC++] - 21 May 2007 19:26 GMT

> What's the CLI equivalent of the empty catch?
>
> i.e.
> try{}
> catch
> {}

How about this:

try
{
Console::WriteLine(L"Hello World");
}

catch ( Exception^ )
{
}

Regards,
Will

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David Anton - 22 May 2007 01:54 GMT

try
{
}
catch(...)
{
}

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> What's the CLI equivalent of the empty catch?
>
> i.e.
> try{}
> catch
> {}

Reply to this Message

SvenC - 22 May 2007 06:39 GMT

> What's the CLI equivalent of the empty catch?
>
> i.e.
> try{}
> catch
> {}

Where is that empty catch allowed? It is not standard C++. Do you mean
catch(...) ?

--
SvenC

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Carl Daniel [VC++ MVP] - 22 May 2007 17:53 GMT

>> What's the CLI equivalent of the empty catch?
>>
[quoted text clipped - 5 lines]
> Where is that empty catch allowed? It is not standard C++. Do you mean
> catch(...) ?

It's allowed in C#. It's equivalent to the C++/CLI construct:

try
{
}
catch(Exception^)
{
}

Using catch(...) will also catch native exceptions, and possibly structured
(platform) exceptions, depending on the compiler options used.

-cd

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Jochen Kalmbach [MVP] - 22 May 2007 22:00 GMT

Hi Carl!

>>>What's the CLI equivalent of the empty catch?
>>>
[quoted text clipped - 11 lines]
> {
> }

No. "catch(Exception^)" is *not* the same as "catch" in C#!

"catch(Exception^)" will *only* catch exceptions which are derived from
"System.Exception"!

"catch" will catch *all* Exceptions (derived from "System.Object")!
It also will catch native exceptins in C#!!!

Therefor the C++/CLI equivalent of "catch" is "catch(System::Object^)" !

See also: Basic Concepts in Using Managed Exceptions
http://msdn2.microsoft.com/en-us/library/df24ysb6(VS.80).aspx

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Greetings
Jochen

My blog about Win32 and .NET
http://blog.kalmbachnet.de/

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Carl Daniel [VC++ MVP] - 22 May 2007 22:05 GMT

> Hi Carl!
>
[quoted text clipped - 21 lines]
> "catch" will catch *all* Exceptions (derived from "System.Object")!
> It also will catch native exceptins in C#!!!

Egads!

I'd forgotten that the CLR actually supporting throwing something not
derived from System.Exception!

-cd

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Ben Voigt - 22 May 2007 23:40 GMT

> It also will catch native exceptins in C#!!!

Wouldn't catch (Exception^) do so as well, giving an SEHException? Or is
that only for p/invoke?

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Jochen Kalmbach [MVP] - 23 May 2007 07:23 GMT

Hi Ben!

>> It also will catch native exceptins in C#!!!
>
> Wouldn't catch (Exception^) do so as well, giving an SEHException? Or is
> that only for p/invoke?

SEHException is also derived from "System.Exception". But you can throw
*any* object as an exception. Therefor, if you want to catch *all*
exceptions, you need to catch "System.Object" instead of "System.Exception"!

See:

#pragma unmanaged

void Test1()
{
throw 1;
}

#pragma managed

void Test2()
{
throw 2;
}

void Test3()
{
throw gcnew System::Object();
}

int main()
{
try
{
Test1();
}
catch(System::Object ^o)
{
System::Console::WriteLine("Test1: " + o->GetType()->ToString());
}

try
{
Test2();
}
catch(System::Object ^o)
{
System::Console::WriteLine("Test2: " + o->GetType()->ToString());
}

try
{
Test3();
}
catch(System::Object ^o)
{
System::Console::WriteLine("Test3: " + o->GetType()->ToString());
}
}

Output is:
Test1: System.Runtime.InteropServices.SEHException
Test2: System.Runtime.InteropServices.SEHException
Test3: System.Object

Greetings
Jochen

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Ben Voigt - 23 May 2007 14:19 GMT

> Hi Ben!
>>> It also will catch native exceptins in C#!!!
[quoted text clipped - 8 lines]
>
> See:

I wasn't doubting that catching System.Object will catch all exceptions...
but wouldn't catching System.Exception also catch all exceptions, decoding
managed objects derived from Exception, and wrapping everything else in
SEHException?

> #pragma unmanaged
>
[quoted text clipped - 52 lines]
> Greetings
> Jochen

Reply to this Message

Jochen Kalmbach [MVP] - 23 May 2007 14:33 GMT

Hi Ben!

> I wasn't doubting that catching System.Object will catch all exceptions...
> but wouldn't catching System.Exception also catch all exceptions, decoding
> managed objects derived from Exception, and wrapping everything else in
> SEHException?

I don't understand the background of this question?

I don't know the internals of every assembly; so I don't know if
"System.Exception" will catch *all* exceptions... regardless of
SEHException...

Greetings
Jochen

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Mattias Sjögren - 23 May 2007 19:37 GMT

>> I wasn't doubting that catching System.Object will catch all exceptions...
>> but wouldn't catching System.Exception also catch all exceptions, decoding
[quoted text clipped - 6 lines]
>"System.Exception" will catch *all* exceptions... regardless of
>SEHException...

You can also use the RuntimeCompatibilityAttribute on your assembly
with WrapNonExceptionThrows = true to make sure all exceptions you see
are derived from Exception (if they aren't already, they get wrapped
in a RuntimeWrappedException). That's what C# does for example.

Mattias

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Mattias Sjögren [C# MVP] mattias @ mvps.org
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DaTurk - 22 May 2007 19:50 GMT

> > What's the CLI equivalent of the empty catch?
>
[quoted text clipped - 8 lines]
> --
> SvenC

My apologies, I was refering to c#

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Jochen Kalmbach [MVP] - 22 May 2007 22:01 GMT

DaTurk schrieb:

> What's the CLI equivalent of the empty catch?
>
> i.e.
> try{}
> catch
> {}

try {}
catch(System::Object^)
{}

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