Help passing array to dll error 998 ERROR_NOACCESS ?

[Delphin25]

Hello,

I'm trying to pass an array to a dll in a sub VI and it wont work, our dll func keeps returning error 998. I believe this is the Windows error ERROR_NOACCESS

Ive attached the vi.

I'm Using Array Data pointer 1D array of unsigned 8 bit bytes

The dll func returns either a 4 6 or 12 byte array depending on which board its talking too.

A previous contractor that wrote this  vi claims the 4 byte version was working but I cant get either to work.

Several customers have tried to do this and all have faled.

At this time we cant change our C dll.

I'm using LabView 7, I just got approval to buy LabView 2010, I'm not sure if that will help this issue though.

using WinXP Pro

Any suggestions would be greatly appreciated.

Is there a way to pass a fixed length array in as a pointer? Cant seem to figure thast out. Cluster?

I'll keep working on it and searching for clues here in the forum.

Cheers,

Richard

[Delphin25]

OK still working on this one.

It looks like we report this error in our driver when someone passes a NULL pointer or a pointer to an array that is too short and we cant do a proper copy of the buffer or a write to the buffer array.  so what exectrly gets passed down from LabView??? from my reading so far it looks lik its like "unsighned char Buffer[]"  which should work fine, also we dont resize the array at any time just basically write 4, 6 or 12 (8 bit) bytes to it.  Any suggestions? writing a CIN doesnt seem like a practical solution.  Ive checked and tested all the CLFN configure possibilities.  Labview reports #0 for the array going into the CLFN or comming out?  Is Labview sending a NULL pointer to our dll???

[Delphin25 · Accepted solution]

Maria from tech Support is a Goddess!!!!!!!!!!!!!!!!!!

The key was to have an array input as I was doing, but then set it to ones "1" non zero value.  I had created a 6 wide array but left the values at the default zeros which was in effect uninitialized or NULL  buffer[0] = 0 hence buffer[] or *buffer is NULL pointer which blew chunks in our driver LOL  . whats funny is in Labview even if i set the values back to 0's its doesnt revert back to null it still thinks its a 6 element array.  Have to look into how to init this thing to 0 properly but 1's are fine to ensure for customers its not null.  thanks all for looking.

[Taki1999]

To ReInit your array from the front panel, right click on the control then Data Operations->ReInitialize to Default or Data Operations->Empty Array.

If you're doing this from a block diagram, you should just be able to reinit by using an array constant.

[Delphin25]

Yeh I attached the fixed version for comparison.

But your right if I set the values to 12 zeros then right click  data operastiom "make current value default" then reinitialize to defaults then it stay as a 12 element array and works.  as indicated in run mode with highlight execution on, it shows up as a #12 instead of #0

Now if I make it a constant instead of a control or indicator it works the only difference is now if you look at the block diagram the 0-11 elements are bold and 0 instead of grayed out and zero which is uninitialized that the key.  So if i leave it like that and just make a big note to users in the comments and on the sub vi fp too to leave this alone or you will cause the bug again I should be fine also leave it at index 11 so they can see its initialized to zeros.  Thanks for the reply. Interesting stuff.