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Is there a decompiler for LABView v4-v6

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One of our customer (Pharma industry) has a compiled LABView application running on Win98 for +10 years. The source code is not available and it seems nobody knows what's under the hood. Based on Win98 dates, I expect them to run a LABView version between v4 and v6.


Is there a decompiler software, any ways to look at the source code or to retrieve some basics information to start reverse engineering.


Thanks for you answers!



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Message 1 of 8

I have never seen/read/heard that a tool like this exists. Maybe someone from NI knows more ...

The LabVIEW application builder usually removes the front panels and block diagrams from most VIs when building an EXE. It would be interesting to see what a decompiler would produce.

Message 2 of 8

I never tried it, but I recall hearing that in older versions of LV executables were a special kind of folder or compressed file.  Try moving a copy of the executable to a different computer with the LV development environment. Then change the extension from .exe to .llb and see if you can open it.  You may need an older version of the LV development system, depending on what version the executable was in.


This was changed a few years ago and definitely does not work with newer versions.



Message 3 of 8

I don't believe there's a decompiler available for any version of LabVIEW.  However, in older versions of LabVIEW (prior to 8, if I'm not mistaken) a compiled LabVIEW application was pretty much a ZIP file with all the VIs inside.  Try renaming a copy of the application, replacing the .EXE extension with .ZIP, then see if you can look inside it.  You might be able to get a list of all the VIs, and with some luck they will have been named in a way that gives you some clues.  If you get this far, and you can identify and install the correct version of LabVIEW (probably including patch release), you might then be able to drop those VIs into the block diagram of a new VI.  You won't be able to see the front panel or block diagram but you'll at least be able to identify the terminals of the subVIs and see the output with different inputs.


EDIT: looks like Lynn beat me to it, and is correct that the rename should be to .LLB, not to .ZIP.

Message 4 of 8
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The whole issue is a little bit more complicated. Before LabVIEW 8.6 the internal executable resource was indeed a LabVIEW VI archive (LLB) and since LLBs have only one hierarchy depth it is basically like a single directory. This caused troubles with the newer LV library based instrument drivers and also LVOOP classes which use the same VI name but with a different library prefix each, so that LabVIEW had to move those files to external directories when building executables, in order to avoid naming collisions.


In all newer LabVIEW versions the internal executable resource in which the VIs are stored is in fact a ZIP file by default. You still can force LabVIEW to use an LLB format to store the files, by enabling the "Use LabVIEW 8.x file layout" in the Advanced build options. Now the ZIP resource was in the beginning stored as simple ZIP formatted data resource and that caused some problems since most ZIP utilities simply scan a file for the ZIP file header and open it as such, even if the actual ZIP file resource is anywhere inside the file, so that almost all ZIP tools could open a LabVIEW executable. NI changed that format so that ZIP tools can not recognize it anymore.


Now, yes you could look into the LLB and ZIP resource in the past (and still can with some extra effort) but before anyone screams "Ohhh my precious IP is on the street" please be aware that the only thing you can do from such a resource is to get the VI names and if you manage to load it into the exactly right LabVIEW version drop the generic icons onto a diagram to see the connector pane. Unless of course you also check the "Enable debugging" checkbox in the Advanced build options, which will leave the diagrams and frontpanels in the VIs, and in fact create something similar to a packed source distributions.


So without the Enable debugging build option, someone gets in fact not much more than what he can do by opening any binary DLL created from C, C++, or whatever mainstream compiler with the dependency tool from Microsoft and MUCH MUCH less than what you can get by simply putting such a DLL through a disassembler.


And to my knowledge there does not exist any disassembler like tool for LabVIEW VIs so far, and I would consider about one billion things more worthwhile to do than attempting to create such a thing.

Rolf Kalbermatter
Averna BV
Message 5 of 8

Thanks everyone, you guys are awsome!


I will gather additional information from the client such as LV exact version, existing documentation, "debug" feature enabled or not...  But, based on you answers, my expectation went from "It might be possible" to "Let's find another way".



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Message 6 of 8

Actually before LabVIEW 8.0 or so there was no officially sanctioned way to create executables that would not have removed diagrams. There was some Application Builder utility from OpenG that would open up some extra features to the application build process, but it had many other issues from using undocumented LabVIEW interfaces so I doubt it was ever used in commercial grade applications.


And 1998 would be at best LabVIEW 5.0, definitely not 6.0 which was released around 2000. Even 5.1 (and certainly 5.1.1 which was a very stable version back then) is not really likely.

Rolf Kalbermatter
Averna BV
Message 7 of 8

As the previous posters have said, the older ".exe" were in fact .llb files. You can, if it is opened in the correct version of LabVIEW, drop the sub-vi's onto a blank diagram and get names and connector types, which, if the program is complex, will tell you little. If the original programmer was very verbose and descriptive in naming the sub-vi's you might get an idea of what they do, but no structural info (other than provided by the input and output connectors, a real jigsaw puzzle!) to tell you how it fits together, just essentially a bunch of "black boxes" without any indication of what goes on within them. Much better to get a detailed requirements document of what the customer thinks/wants the tester to do and build it from scratch. Any changes to the existing program, if it were possible, would require requalification testing anyway, so building from scratch is a good idea. The real critical aspect though, is the detailed requirements document!   Good Luck!



P.S. The question of decompilers has come up since the introduction of the exe around v4, and the general consensus has been that none exists.

Certified LabVIEW Developer

Senior Test Engineer North Shore Technology, Inc.
Currently using LV 2012-LabVIEW 2018, RT8.5

LabVIEW Champion

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