I have a class constructor which is supposed to signal failure by
raising an exception. Here is the code for the constructor:
Sub Constructor(Key As Integer, Size As Integer)
Soft Declare Function GetShm Lib "libc" Alias "shmget" (theKey As
Integer, Size As Integer, Flags As Integer) As Integer
Soft Declare Function Attach Lib "libc" Alias "shmat" (shmid As
Integer, Addr As Ptr, Flags As Integer) As Ptr
Dim ID As Integer
Dim P As Ptr
Dim err As NilObjectException
ID = GetShm(Key, Size, Bitwise.BitOr(0600, ipc_creat))
If ID = -1 Then
ShowError "Get failed with the error: " +
libcErrorMessage(ErrorCode)
Raise err
End If
P = Attach(ID, Nil, 0)
If P = Ptr(-1) Then
ShowError "Attach failed with the error: " +
libcErrorMessage(ErrorCode)
Raise err
End If
TheMemory = P
End Sub
Here is the code from which the constructor is being called (in the open
event of the main window):
Try
SharedMem = New SharedMemory(Key, StructSize)
Catch Err As NilObjectException
Dim MD As New MessageDialog
MD.Icon = MessageDialog.GraphicStop
MD.ActionButton.Caption = "Ok"
MD.Title = "Fatal Error"
MD.Message = "The shared memory block could not be created. The
program will exit."
Call MD.ShowModal
Quit
End Try
The routine ShowError simply puts up a messagedialog with the passed
error message.
When the program is run in an environment which ensures that the call to
GetSHM will return -1, the error for the call to GetSHM is displayed,
then an error for the call to Attach is displayed, then the program
exits.
Questions:
1. If an exception is being raised after the call to GetSHM, how is the
program getting to the call to Attach?
2. Why is the exception handler in the Catch not being called?
Obviously, there is something that I don't understand about exception
handling in RB.
Paul Dobbs
Software Engineer, Staff
Lockheed Martin Missiles and Fire Control
Phone (972) 603-1244
Fax (972) 603-2017
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