I am getting memory cold not be read errors

[jimmerriman]

I am running LabView 8.2.1 on windows XP.  I am communicating with a USB device through a DLL. I am getting windows errors that state the instruction at 0X00000000 referenced memory at 0X00000000 the memory could not be read. (The locations are never the same that’s why I used zeros).  All the DLL call work fine on an individual basis. When I get this message LabView locks up and disappears I have tried monitoring the memory but the monitor disappears also. It doesn't happen at the same place in the program,  in happens at the beginning the end and everywhere in between.

Any ideas would be greatly appreciated.

[Steve.Briggs]

A few questions...

• Have you had any prior success with the device?
• Do you have enough time to take a snapshot of the error messages?
• Have you tried capturing anything using NI Spy?

[jimmerriman]

• The device works fine using the same DLL in some C++ applications.
• I can take a snap shot of the error but all it says is exactly what I wrote "The instruction at 0X3038ff90 referanced memory at 0X00000008 the memory could not be read"
• I have not tried NI Spy, I will do that but all other tries to use NI debug have failed for the reason that when it bombs it takes everything.

[smercurio_fc]

Those kinds of errors are usually due to stomping over a part of memory that you shouldn't be touching. Likely cause is the allocation of memory, or non-allocation of enough memory. Even if the DLL call works once by itself doesn't mean it isn't messing up with memory, and causing subsequent calls, or calls to other functions to crash LabVIEW. Are any of the DLL calls using arrays, or strings? Do you see "void *" in any of the argument types?

[jimmerriman]

There are some strings I don't see any voids

[smercurio_fc]

OK. Are these strings inputs or outputs of the DLL call? If they're outputs you need to preallocate the string. I'm not saying this is the issue since we can't see your code unless you post it and the DLL. At the moment there's little to go on other than the fact that you're getting a crash when you call a DLL from LabVIEW, and the specific DLL call that causes the crash is random. Like I said, not much to go on.

[jimmerriman]

Let me back up a bit. The crash doesn't always happen when calling the DLL I am also sending and retreaving from a microsoft access database and it happens then also, and it happens when I have a window pop up to enter indentifying data about the test and I am not actually sending or receiving anything.

[JamesR]

Hi Jim,

Would the crash happen if you never called any of the DLLs, but left the rest of your code the same?  Here is a KnowledgeBase that talks about DLLs and LabVIEW crashing that might be helpful.

Why Does LabVIEW Crash When I Call My DLL?