- 4.62.1.6 -
Standard Units
System Unit
System Unit VariablesErrorAddr variable
Targets: MS-DOS, OS/2, Win32
System Unit
ExitProc, ExitCode, and ErrorAddr variables
are used to implement exit procedures.
The ExitProc pointer variable allows one 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.
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- 4.62.1.6 -