MATLAB: Mex: linker does not seem to be able to access external lib file; -l & -L options not helping

external librarylinkermex

For a project for college I need to write an S-Function in Matlab to acquire data from a data acquisition device (NI USB-6008).
I've been reading the on-line help and I've successfully compiled a simple S-Function.
Then I added to my basic S-Function (NI_USB_6008_AnalogInput.c):
#include "NIDAQmx.h"
and then added this declaration to the function 'mdlOutputs':
TaskHandle taskHandle = 0;
(The 'TaskHandle' type is declared in the header file above.)
That compiles.
However, when I try to call a function from the NIDAQmx library:
DAQmxCreateTask("", taskHandle);
I get the following error:
>> mex NI_USB_6008_AnalogInput.c
Writing library for NI_USB_6008_AnalogInput.mexw32
c:\docume~1\l10\config~1\temp\ni_usb_6008_analoginput.obj .text:
undefined reference to '_DAQmxCreateTask@8'
    C:\ARCHIVOS DE PROGRAMA\MATLAB\R2006A\BIN\MEX.PL: Error: Link of
  'NI_USB_6008_AnalogInput.mexw32' failed.
??? Error using ==> mex
Unable to complete successfully
(I tried two compilers: the default one, LCC, and MS Visual C++ 2005, the error is similar with both of them.)
The problem, I understand, is that the compiler generates an object file with the correct reference to the function I'm trying to call, but then the linker is unable to access that function from the NIDAQmx.lib library. (Both the header and the library files are in the same directory as the source file.)
I tried using the -l and -L options to MEX and adding the .lib file at the end of the mex command, but I still get the same error message.
(I shuold add that I could successfully compile a simple C file with calls to the NIDAQmx library using MS Visual C++ 2005, but in Matlab I get the linker error, even when Matlab is configured to use the MS compiler.)
Can anyone suggest a solution?
FWIW, I'm running Matlab R2006a (7.2) on Windows XP with SP2.
Thank you.
Ignacio

Best Answer

For lack of a better solution, here's what I'm doing.
I removed the following libraries:
  • user32.lib
  • gdi32.lib
  • winspool.lib
  • comdlg32.lib
  • advapi32.lib
  • shell32.lib
  • ole32.lib
  • oleaut32.lib
  • uuid.lib
  • odbc32.lib
  • odbccp32.lib
from this file:
C:\Documents and Settings\{USER}\Application Data\MathWorks\MATLAB\R2006a\mexopts.bat
Using MS Visual C++ 2005 it compiles correctly.
The correct way to do it would be to make the compiler/linker see the libraries above. It's not clear to me why it cannot access them, but I haven't looked much into it. What I just described is a quick & dirty solution. Hope it helps someone else who runs into this problem -- at least to get things to work!
Related Question