ErrorAddr, ExitCode, and ExitProc (variables) (System unit)

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  ErrorAddr, ExitCode, and ExitProc (variables)     (System unit)


ExitProc, ExitCode, and ErrorAddr variables are used to implement exit procedures.

The ExitProc pointer variable allows you to install an exit procedure.The exit procedure always gets called as part of a program's termination.

An exit procedure takes no parameters and must be compiled with a far procedure directive to force it to use the far call model.

When implemented properly, an exit procedure actually becomes part of a chain of exit procedures.The procedures on the exit chain get executed in reverse order of installation.

To keep the exit chain intact, you must save the current contents of ExitProc before changing it to the address of your own exit procedure.

The first statement in your exit procedure must reinstall the saved value of ExitProc.

An exit procedure may learn the cause of termination by examining the ExitCode integer variable and the ErrorAddr pointer variable.

  ■ In case of normal termination, ExitCode is 0 and ErrorAddr is nil.
  ■ In case of termination through a call to Halt, ExitCode contains the
    value passed to Halt and ErrorAddr is nil.
  ■ In case of termination due to a run-time error, ExitCode contains the
    error code and ErrorAddr contains the address of the statement in error.

The last exit procedure (the one installed by the run-time library) closes the Input and Output files. If ErrorAddr is not nil, it outputs a run-time error message.

Once the run-time library has called all exit procedures, it returns to Windows, passing as a return code the value stored in ExitCode.

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