Error 6: Invalid handle

[Tim J]

Today one of my apps started getting an Invalid handle error when doing a dbseek()

Been using it for years and I have never actually seen this particular error before.

Can anyone give me a steer about what to look for?

[Tim J]

It was doing a seek on an already open file: one of about 50

It had just updated the same file a bunch of times.

At first I wondered if it might be index corruption, but reindexing it did not help

I recently changed to the Harbour 3.2.0dev (r2301231146) build.

I don't know if that is cause or coincidence.

Any help would be appreciated

[Przemyslaw Czerpak]

Hi,

You have very serious bug in your code and you will have to

check all calls to FClose() or similar function.

It's not the first time someone reports such thing.

One of the most funny situation was when I received from user

DBF file with printer output inside. It was caused by double call

to FClose( nStaticVar ).

The first call closed correct file. Then SET PRINTER TO <cFile>

was executed and then file handle reused. The second call to

FClose() closed this handle and it was reused again by dbUseArea()

but still SET PRINTER TO was active with the same handle number

as the one used by DbUseArea(). What happened you can imagine.

The report directed to printer ended in DBF file corrupting it.

The buggy code was used for many years and suddenly some

other modifications which changed the order in which OS allocated

handles for running application exploited it.

Changing Harbour version does not help you. Of course it possible

that you mask the problem for some time but it will return and the

results can be much worse .

best regards,

Przemek

W dniu 31.01.2023 o 19:46, 'Tim J' via Harbour Users pisze:

Today one of my apps started getting an Invalid handle error when doing a dbseek()

Been using it for years and I have never actually seen this particular error before.

Can anyone give me a steer about what to look for?

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[Tim J]

Wow!  Thank you very much, Przemek!

Just what I need to know.

Now to find it.