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How to make VEE release a resource!!

Question asked by Sima on Sep 28, 2016
Latest reply on Sep 29, 2016 by Sima

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Hello,

I have a problem with imported dlls in VEE. I have developed a test program, test.vee, which imports 2 dlls to control a wifi device and a wifi test instrument.

If an error occurs in the external routine and the routine fails, VEE locks some resources and keeps the connection to instrument. How can I make VEE to release the resources and terminate the connection.

I start the instrument from another instance of the same program(test.vee) and it works as normal. If I close and open the failed program it will also work. So, I guess that although the program is not hanging, it is in a state that needs a reset to come out from.

The same problem happens if I stop the test program in the middle of running by pressing stop button. Then to start again will fail until I close and reopen VEE.

I appreciate any advice. Thanks

Best Regards

Sima

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Mike Sep 28, 2016 10:23 AM

Not all DLLs are the same - you didn't give us any clue as to what type of DLL or how you're importing it! If you are importing it as a compiled library ( unlikely for a modern API ) then you can use Device -> Delete Library VEE object. For a .NET object, I typically set a local variable to the top-level object. In that case you can use Data -> Variable -> Delete Variable to delete the reference to the object.

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Sima Sep 29, 2016 1:17 AM

Hello Mike,

It is a compiled library that I import using Import Library object. However I delete the library at the end when the error happens, and starting again, the test imports the library and calls the functions. Still when some functions (not all of them!!) are called they fail. For example there is this function which checks the tester type and model and sets some parameters for the tester and when it is called in REstarted situation, it returns "No Connection to the tester". As you can see reading the error string from the instrument is another function of the same dll which works!!!

My guess is that there is memory allocation problem to some function's input that causes this problem. One should be careful about arrays and string type pointers when importing dlls.

Acording to the VEE manual:

"For a string input, use a Formula object. Delete the data input terminal from the Formula object and enter an expression like 256*"a". This creates a string that is 256 characters long (plus a null byte) filled with a’s."

I also have a tiny question here what if I want to initialize the input? Say we have "this is a file name" as input A to formula object and enter something like 1*A. Is it a correct way to do this?

Although I have been careful, it seems somewhere the useful data in the memory is overwritten (which I am trying to find in parallel). But, even if something goes wrong, a clean automated sw restart without closing and opening VEE is desirable.

Thanks for taking the time to help

Sima

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Mike Sep 28, 2016 10:23 AM
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Not all DLLs are the same - you didn't give us any clue as to what type of DLL or how you're importing it! If you are importing it as a compiled library ( unlikely for a modern API ) then you can use Device -> Delete Library VEE object. For a .NET object, I typically set a local variable to the top-level object. In that case you can use Data -> Variable -> Delete Variable to delete the reference to the object.
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Sima Sep 29, 2016 1:17 AM
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Hello Mike,

It is a compiled library that I import using Import Library object. However I delete the library at the end when the error happens, and starting again, the test imports the library and calls the functions. Still when some functions (not all of them!!) are called they fail. For example there is this function which checks the tester type and model and sets some parameters for the tester and when it is called in REstarted situation, it returns "No Connection to the tester". As you can see reading the error string from the instrument is another function of the same dll which works!!!

My guess is that there is memory allocation problem to some function's input that causes this problem. One should be careful about arrays and string type pointers when importing dlls.
Acording to the VEE manual:
"For a string input, use a Formula object. Delete the data input terminal from the Formula object and enter an expression like 256*"a". This creates a string that is 256 characters long (plus a null byte) filled with a’s."
I also have a tiny question here what if I want to initialize the input? Say we have "this is a file name" as input A to formula object and enter something like 1*A. Is it a correct way to do this?

Although I have been careful, it seems somewhere the useful data in the memory is overwritten (which I am trying to find in parallel). But, even if something goes wrong, a clean automated sw restart without closing and opening VEE is desirable.

Thanks for taking the time to help
Sima
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How to make VEE release a resource!!

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