Calling primary dll which calls secondary dll

Hi all
I have a visual C++ file which calls a dll named mpusbapi.dll . The visual C++ file has some additional
functions also. I want to make this visual C++ file itself a dll and then call this dll from call library function
in labview. Please guide me in making this visual C++ file dll.
To make functions visible in call library function what do i use.
_declspec (dllexport) or Extern C
I have also read the tutorial of making Writing a DLL with Microsoft Visual C++
Are there any steps required in doing this? Please tell
Regards

I want to add one more thing that in the tutorial of Writing Win32 Dynamic Link Libraries (DLLs) and Calling Them from LabVIEW
What is this for
BOOL WINAPI DllMain (
            HANDLE    hModule,
            DWORD     dwFunction,
         LPVOID    lpNot)
    return TRUE;
Is it necessary to write this in order to create our own dll?

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=========================
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Error 1073 when building LabVIEW app which calls LabVIEW dll

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I have found a temporary workaround in which I created a dummy dll that removed all functionality from exported vis but had the same name and function signatures. I then built the application using this dummy dll. Once complete, I replaced the dummy dll with the real dll.
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Is there a way to allow DLLs to call sup-application in TestStand?

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I've got a TestStand sequence that calls a DLL function which is generating an EAccess Violation.
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Thanks,
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Hi Marek D,
This question appears to be related to another post that you and I were working on before. Does this post -> http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=50650000000800000040520000&UCATEGORY_0=_8_&UCATEGORY_S=0 <- have anything to do with what you are asking now? If it does did you try the suggestion that I mentioned last in the other thread? Your use of the dll in TestStand does not follow the exact same pattern as what you demonstrated in CVI, and this would be a good starting point.
To answer your question though, no, TestStand does not have a problem with a dll that it loads and invokes functions on trying to spawn new threads. This is a rather common scenario in fact. As I stated before it appears that since th
e dll is loading fine and TestStand is able to access its functions ok, there is not really a problem with how TestStand interacts with the dll. In fact if there were a specific problem dealing with this dll trying to create additional threads there could indeed be a problem in that its threads are not being managed properly from within inside the dll itself. Trying to guess at how the dll operates is generally a timewaster, unless you know its exact requirements you may never be able to get it to work. It appears that there is either an external dependency you are not taking into account with this particular dll or you are using it improperly in TestStand. Trying my previous suggestion of trying to reproduce the CVI setup exactly is your best bet.
Jason F.
Applications Engineer
National Instruments
www.ni.com/ask

Call multiple functions from same dll with call library function

hi,
i am working on a project in wich we need to make a UI to read out a sensor network.
the UI should be usable in any project, but every node needs a different piece of code depending on the type of sensor with wich it is equipt.
so i need to be able to call different pieces of code when i need them, and still be able to use the UI in future projects with possibly new types of node we now don't have.
so someone told me to use DLL's, cause then i would be able to call the code i need the moment i need it.
but i have never worked with DLL's (just learned about this option 3 day's ago) so i have a question.
i know i can dynamicly change the DLL i call with the call library function, but can i dynamicly change the function i call from that DLL ?
or do i have to put a new call library function for each function i want to call, even if its from the same DLL ?
kind regards,
stijn

nazarim wrote:
ok so there is no (easy and ubderstandable) way for me to dynamicly change wich function i want to call from a certain DLL.
but now i started wondering, the path on the call library function is not ment to dynamicly change a DLL
but it does work so, if i am carefull, can i use it for that purpose or will labview give me a series of problems once i start using it in larger programs ?
Thepath on the Call Library Node can be used to load a different DLL. Obviously since you can't change the function name your other DLL would have to export exactly the same function name and of course with the same parameters. This is seldom the case so it is not the main use of the path input to the Call Library Node. It's main use is as indicated to load DLLs at runtime rather than at load time of a VI. So that an application can run even when the DLL is missing, until the moment the functionality from that DLL is needed.
If you can make sure that all your DLLs export the same function name with the same parameter you can use the Call Library Node to call into different DLLs through the path input. If however you would need to call different function names you would have to resolve to some DLL which does do the dispatching and invocation using LoadLibrary() and GetProcAddress(). But unless you need to go with DLLs for some reason using the Call By Reference Node can give you an even more flexible approach.
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Using an external DLL with "Call Library Function"

Hi!
I am trying to use an external DLL which is used from Visualbasic & Delphi:
http://www.keb.de/common/tools/KEBCOMDriver.zip
the protKEB.dll accesses the serial port to control an KEB frequency
inverter.
Unfortunatly there is no prototype header file for the DLL (no help on that
from KEB).
I only have a VisualBasic example program which works with the DLL.
(Unfortunatly I am no Visual basic expert)
To initialize the com port I have to use the function: setprotproperties &
getprotproperties
they are declared as:
'Setting the protocol properties
'ctrl is a pointer to a data structure of type tProtProperty
Declare Sub setprotproperties Lib "protkeb.DLL" (ctrl As Any)
'Reading the protocol properties
'ctrl is a pointer to a data structure of type tProtProperty
'the desired protocol is entered in ctrl.prottype before calling
Declare Sub getprotproperties Lib "protkeb.DLL" (ctrl As Any)
and tProtProperty is:
Public Type tProtProperty
ProtType As Long 'Type of Protocol (tProt)
TimeOut As Long 'ALL protocols
Baudrate As Long 'ANSI, HSP5
Comport As Long 'ANSI, HSP5
Flag As Long 'ANSI, HSP5: 01 = Sendslow
/ IP: 01 = UDP
Port As Long 'IPort number
Txtlen As Byte 'IP : length of following
text or 0
txt As String * 100 'IP : IP-Address or name
(maximum length)
End Type
I already tried to use a cluster with tProtProperty entries as an Input for
the function
setprotproperty in a call library function with:
Parameter Type : Adapt to type
Data Format: Pointer to Handle
but I always get an "exception within external code....."
What am I doing wrong?
How does a cluster & a "call library function node" look like that works?
Any help is really appreciated!
thanks
tom
,-Thomas Kerberger Physikalisch-Technische Bundesanstalt-.
| Abbestr.2-12 D-10587 Berlin fon: +49-30-3481338 |
| mailto:[email protected] fax: +49-30-3481386 |
`--------Labor 7.33 Messung thermischer Energie---------'

Thomas,
LabVIEW cannot call a DLL that has structures directly, you will need to create either a wrapper DLL or CIN that will take in all of the data individually construct the structure, and send it to the DLL function.
For more information on what a cluster looks like in native code, I would suggest creating a simple cluster, creating a Call Library Function Node on the block diagram with a cluster input. Then right-click on the Call Library Function Node and choose "Create .c file". This will generate the data structure for the cluster and give you a better feel for it. I would then suggest going to the Using External Code in LabVIEW manual that can be found in the LabVIEW Bookshelf (Start»Programs»National Instruments»LabVIEW 6»LabVIEW Manuals or »LabV
IEW 6.1»Search the LaBVIEW Bookshelf).
There is also the following: Developer Zone: Passing a Variety of Data Types from DLL to LabVIEW.
Randy Hoskin
Applications Engineer
National Instruments
http://www.ni.com/ask

How to call LabVIEW dll from ATL COM dll

I have tried to call simple LabVIEW 8.6 Dll from win32 test application, class Library.
I have include LabVIEW generated SharedLib.h file and SharedLib.lib file in the test application which I created as simple win32 console project and also from win32 class Library. I was sucessfully able to call my LabVIEW dll funtion.
But when I create ATL COM project and try to add SharedLib.h file and SharedLib.lib file I used to get following erors
Error 1 error C2733: second C linkage of overloaded function 'StrCatW' not allowed d:\program files\national instruments\labview 8.6\cintools\extcode.h 463
Error 2 error C2733: second C linkage of overloaded function 'StrCpyW' not allowed d:\program files\national instruments\labview 8.6\cintools\extcode.h 464
Error 3 error C2733: second C linkage of overloaded function 'StrCpyNW' not allowed d:\program files\national instruments\labview 8.6\cintools\extcode.h 465
Error 4 error C2733: second C linkage of overloaded function 'StrCmpW' not allowed d:\program files\national instruments\labview 8.6\cintools\extcode.h 466
Error 5 error C2733: second C linkage of overloaded function 'StrCmpNW' not allowed d:\program files\national instruments\labview 8.6\cintools\extcode.h 467
these many errors.
Will some one explain me how to call LabVIEW dll from ATL COM dll.
Thanks & Regards,
Jay

I also had this problem. My application is unicode-aware, but I was attempting to link it to a library with primitive C-string arguments. You could dynamically load the DLL as suggested (more work), modify the header files (really not recommended), or if you are feeling lucky you could try fooling the compiler, as I was successfully able to do in Visual Studio 2010, by steering the preprocessor around those functions (assuming you're not using them, of course -- otherwise this probably wouldn't work):
// prepare for NI extcode.h inclusion. avoid linker errors for this project.
#define StrCatW(a,b)     IgnoreLinkError_StrCatW(a,b);
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#define StrCpyNW(a,b,c) IgnoreLinkError_StrCpyNW(a,b,c);
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#include <MyLibraryHeader.h>
// clean up afterwards, put things back to 'normal'
#undef StrCatW
#undef StrCpyW
#undef StrCpyNW
#undef StrCmpW
#undef StrCmpNW

EXEcutable only starting DLL when calling a popup before.

Hello,
1. I have created a DLL in Labview 8.2 with one VI/function.
2. Then i call this DLL/function in a new VI
3. Then i created an EXE-file of this VI (which calls a DLL)
Attached a screenshot of the code.
As you can see it contains a sequence-structure where in the first part i open a message-popup and in the second-part i call the DLL.
When i run it like this then it works without problems.
The funny thing is:
When i remove the message-popup and create a new EXE-file and run it then nothing happens!
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Whats wrong here? Seems like Labview can´t make the DLL-call starting in the second exe-file (without an popup before).
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Attachments:
screen.jpg ‏26 KB

Hmm, i´m getting a red error-message after cklicking on "install LabVIEW 8.2.1 now." in your link.
Whats going wrong here?
--> See attached screenshot
Attachments:
error.jpg ‏54 KB

Can not find size_t during import a dll and calling a function crash labview

Hello, experts
I need to use FingerLakeInstrument DLL ( see the attached) inside Labview to talk to a CCD camera. it is built from microsoft visual studio C++
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During importing the dll, first thing I got is <sys/types.h> ( ie size_t ) cannot be found. I have installed free version of microsoft visual studio C++
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regards
xiaofeng
Solved!
Go to Solution.
Attachments:
libfli-32.zip ‏93 KB

Hi, Smercurio_fc
thanks for your reply. Yes, you are pointing to the right place. I have solved the crash problem.
when importing DLL into Labview using Tools\import\Shared Library (.dll), Labview automatically set the calling convention as C not as stdcall (WINAPI). it is this that later the labview crashes when a function is called. as soon as I manually re-selecte calling convention as stdcall, my test.vi works OK (see attached).
I tried Call Library Function too to call libfli.dll, as long as I select stdcall as call convetion. the test.vi works.
How do I know which Call convention I need to choose if there is no infomation from DLL provider?
as for the size_t,
I add #include <crtdefs.h> in libfli.h and
add additional include path as
C:\Program Files\Microsoft Visual Studio 10.0\VC\include. this solved the "not found" issue.
for this case I know that the DLL is built from VC++, is this right way?
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xiaofeng
Attachments:
test.vi ‏13 KB

Can a VI compiled in dll be called in LV?

Hello,
I have some dll´s, which use some common VIs. This means, each time when I compile a dll, the VI will be compiled within the dll. What habbens, if I compile the same VI in another dll, and call the dlls in the same time. Will be there a collision, that the VI is already loaded , by calling the second dll?
regards
Mitulatbati

Maybe I did not understand the question correctly...
If you have a vi that is compiled into a dll and then from another vi (main) you call both the original VI and the dll, it should not collide as you would be calling different objects.
Have you tried it and having problems?

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Hi
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I am sure Ray F. may have a few tricks up his sleeves... Hope you see this post, Ray!
I compiled a dll using CVI. The dll is called as a test by TestStand.
I do have an "exe" version of the code that I use for debug with a testbed, but the behaviour is not the same as testing the actual target while running TestStand. My goal is to get as close as possible to the real events.
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Sorry about that,
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Regards.

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Calling primary dll which calls secondary dll

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