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- TODO #1069
TODO #1069
Error handling statement (1%) was converted to a complex pattern which might not be equivalent to the original.
Description
This ussually occurs when a Resume Next Error Handling Pattern appears. It is a warning because functional equivalence could not be accomplished in this scenario.
Recommendations
The Resume Next error handling pattern resumes execution of the next statement after an error. In the case of structured error handling, the resulting behavior is more similar to an On Error Go To statement, where the catch statement serves as the Go To label.
For this reason the replacement done by the VBUC might not be the exact funcional equivalent of the original code. In cases where the code is related, meaning if one call fails subsequent calls are likely to fail, then leaving a single try / catch statement could work. Since an error at any point of the process would merely be replicated in the susbsequent.
A common example of this might be file operations, generally if the IO operation fails at the beginning, all subsequent calls will fail.
In other cases, the error pattern of Resume Next is necessary when the code statements are fairly independent a failure in one statement does not affect the error condition of a subsequent call. The code sample illustrate such a case. In order to ensure functional equivalence it's necessary to add a try catch (with empty clause) to each line that can throw an exception. In these cases the main try catch (generated by the VBUC) is less effective and should be removed.
Sample VB6
PublicFunction ComplexErrorPattern() AsInteger
F1(1)
OnErrorResumeNext
Dim I AsInteger
I = 0
I = F2(1)
If I <> 0 Then
I = F4(80)
Else
I = F3(50)
EndIf
Exit_Label:
ComplexErrorPattern = I
ExitFunction
EndFunction
Target VB.NET
PublicFunction ComplexErrorPattern() AsInteger
F1(1)
'UPGRADE_TODO: (1069) Error handling statement (On Error Resume Next) was converted to a complex pattern which might not be equivalent to the original.
Try
Dim I AsInteger = 0
I = F2(1)
If I <> 0 Then
I = F4(80)
Else
I = F3(50)
EndIf
Return I
Catch exc As System.Exception
ThrowNew Exception("Migration Exception: The following exception could be handled in a different way after the conversion: " + exc.Message)
EndTry
EndFunction
Expected VB.NET
PublicFunction ComplexErrorPattern() AsInteger
Dim I AsInteger = 0
Try
I = F1(1)
Catch
EndTry
If I <> 0 Then
Try
I = F2(80)
Catch
EndTry
Else
Try
I = F3(50)
Catch
EndTry
EndIf
Return I
EndFunction
Target C#
publicint ComplexErrorPattern()
{
F1(1);
//UPGRADE_TODO: (1069) Error handling statement (On Error Resume Next) was converted to a complex pattern which might not be equivalent to the original.
try
{
int I = 0;
I = F2(1);
if (I != 0)
{
I = F4(80);
}
else
{
I = F3(50);
}
return I;
}
catch (Exception exc)
{
thrownew Exception("Migration Exception: The following exception could be handled in a different way after the conversion: " + exc.Message);
}
return 0;
}
In this case it may be necessary to add a try catch block for the call to F2, F3 and F4, if the function can throw an exception.
Expected C#
staticpublicint ComplexErrorPattern()
{
int I = 0;
try
{
I = F1(1);
}
catch
{
}
if (I != 0)
{
try
{
I = F2(80);
}
catch
{
}
}
else
{
try
{
I = F3(50);
}
catch
{
}
}
return I;
}
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