Terminal Error 3 (Return without gosub)

[ADAM HARKUS]

We are having problems with RETURN after error handling.

We have a subroutine that at attempts to open a file.
On an error (Ie. TE 71) the user is asked if the program
should re-try the open. If the user selects not to re-try
or re-tries and the file is eventually opened the RETURN
from the subroutine is no longer working.

A terminal error 3 is now reported!

Anyone have any suggestions.



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[Tom Hanlin]

What this means is, your program is making more RETURNs than there
are GOSUBs. Since this appears to be related to your error handler,
you might start by making sure your error handler uses RESUME to return
to the proper place after handling the error. The two things to look
for, here, are: error handlers exit with RESUME, not RETURN; and that
the location being RESUMEd to is the right place to go.

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Tom Hanlin
PowerBASIC Staff

[Davide Vecchi]

In case you are correctely exiting the error handler with RESUME but your subsequent RETURN is still not working, you might also check the compiler option "GOSUB preserve if errors".

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Davide Vecchi
[email protected]

[Lance Edmonds]

Hi Adam,

In addition to those excellent suggestions, you might also like to check that you are testing with _all_ four types of error testing enabled ($ERROR ALL ON), just in case you have a memory corruption caused by say, writing beyond an array boundary, which is causing an "obscure" error to occur later in the program.


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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Mike Luther]

FInding all these things is made much easier, in my experience, if
one includes a numeric line lable down in the subroutines. That way
you get a shorter trip to the zoo to find out which animal has the
bad manners!

It's espectially useful if you are using nested subroutines, and then
doubly so when you are using CALL's to SUB's! As the programs get
bigger and bigger you'll possibly wind up putting your core routines
into a library. You put the next most often ones in a higher level
one, perhaps. Then you'll use these to build upon for ordinary work.

That done, a suggestion that Lance made was probably the most single
valuable one for all of this stuff that I've been taught. Use the
technique of EXIT FAR AT #####. Then use a common error handling section
in your code to do that work. ERL and ERR aren't operationally quite
like the normal variable we all know and love in displaying this and
that .. As you enter the master error routine it sometime helps to
use an equate like EERR% = ERR and VERL& = ERL to gain a little bit
of flexibility in displaying and recalling what went wrong, even
after RESUME work!

It's just my opinion, but a lot of the pain in handling all of this
mess of tracing complex nested errors in PowerBASIC is still traced
to the problem of only handling the error throw traces on the basis
of NUMERIC LINE LABLES.

If we had a way to use ALL LINE LABLES in the error trapping and handling
operations and not just the numeric ones, it would sure make life a
lot easier in my opinion.

Maybe we'll see that in the next incantation of PowerBASIC!


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Mike Luther
[email protected]