Certain types of clusters fail to send over Datasocket or Shared Variable
By
prime8,
in LabVIEW Bugs
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Similar Content
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By Jim Kring
[Update: NI Bug 974336]
There seems to be a bug in the coercion of data to variant when a cluster contains a single element that is a variant. (original post here).
Note: This bug appears to be very old, going as far back as LV2012. This has been reported to NI in the LV2020 Beta forum. I don't have a Bug ID / CAR yet.
Coerce to Variant Fail (LV2019).vi
Note that adding another element to the outer cluster causes the problem to go away.
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By torekp
DLL functions or shared variables? Or something else?
I have a Labview 2014-64 executable (or I can build a DLL) that runs one piece of equipment, the X-ray. The other engineer has a large CVI Labwindows 2015 + MS Visual Studio 2012 (C++) executable that runs everything else. I want the Labview code to be a slave of the CVI code, accepting commands to turn X-ray On or Off, reporting failures, and the like. Translating the X-ray code into C++ would be possible in principle, but not fun.
Shared variables look easy, but I'm kinda scared of them. I would define all the shared variables in my LV code, since I'm more familiar with LV, then use them in both. There's a thread in here called "Shared Variable Woes" so maybe I should be scared. In the alternative, I tried building a proof-of-concept DLL in Labview, and calling its functions in CVI/C++, and it works, but it's kinda clunky. (I'm attaching it below in case you want to play, or advise.)
Your advice would be appreciated.
XrayDLL.zip
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By ShaunR
Maybe others have seen this but I only became aware of it recently so I apologise if there is already a CAR for it.
The following demonstrates a difference in behaviour between LabVIEW 2017 and previous versions (back as far as 2009, maybe further).
The VI registers an event when it starts (in the timeout case) and generates a user event when the Increment button is pressed.
The expected behaviour is that the counter will increment by one every time the button is pressed. This is the case for LabVIEW versions prior to 2017. In 2017, the user event is never fired, nor is there an error emitted by the generate user event.
To get the VI to operate as expected in 2017; change the event refnum tunnel to a shift register. This seems to indicate that the refnum prototype is stomping on the dynamically allocated reference whereas in previous LabVIEW versions it would not. Note also, that when using the shift register, the cases do not need to be "wired through" as would be expected with similar functionality in a normal case statement.
evnt.vi
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By Fred chen
Hi
When I call the DLL, there is a structure:
struct Signal { uint32 nStartBit; uint32 nLen; double nFactor; double nOffset; double nMin; double nMax; double nValue; uint64 nRawValue; bool is_signed; char unit[11]; char strName[66]; char strComment[201]; };
There is another Message structure to the above Signal:
struct Message { uint32 nSignalCount; uint32 nID; uint8 nExtend; uint32 nSize; Signal vSignals[513]; char strName[66]; char strComment[201]; }
The point is Signal vSignals[513];
I've tried to solve it like this，but the program will crash.
How to create struct Message ，any good suggestions? Thanks a lot.
message.vi
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By Tim_S
Thought I'd pass this along and see if anyone can reproduce with different versions of LabVIEW. Appreciate it if anyone has seen this and has a fix.
I'm using shared variables to communicate between applications (1:N). I'd been seeing some memory creep that was inconsistent and somewhat bizarre. Eventually managed to track it down to that I'm programmatically opening a connection to a shared variable in one loop, then reading the value in a different loop (the different loops have to do with reconnecting on connection loss and startup). There is a functional global used to pass the variable to the second loop. The Read Variable primitive deallocates all but 4 bytes of memory for the previous loop handle and then allocates memory for a new handle on each iteration of the while loop, hence creating a leak. This behavior does not occur if there is only one loop where there is an open, while loop with a read, and a close.
Main.vi demonstrates the issue. Main 2.vi is more like the NI example.
I've got service request #7728859 with NI going, but I think I got the guy's first day.
LabVIEW 2015 SP1 32-bit on Win7 64-bit. Shared Variables memory leak.zip
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