Why do I receive error LNK2019 using mex to link to "C" dll

I am trying to compile a mex function to call functions from a set of commercial "C" dll's with an associated .lib file. I am using the following script to execute the mex command:

--------------- script -------------------

% include path bvHeaderPath = 'C:\Program Files (x86)\BlueView\ProViewer SDK 3.6\include'; iPath = ['-I' bvHeaderPath];

% blueview library path %bvLibPath = 'C:\Program Files (x86)\BlueView\ProViewer SDK 3.6\lib'; bvLibPath = 'C:\home\stockel\matlab\mex\blueview'; lPath = ['-L' bvLibPath];

mex('-v', iPath, '-lbvtsdk3', lPath, 'mex_file_sonar.cpp');

----------- end script ------------------

And the result is:

------------ mex output -----------------------

--> cl -I"C:\Program Files (x86)\BlueView\ProViewer SDK 3.6\include" /c /GR /W3 /EHs /D_CRT_SECURE_NO_DEPRECATE /D_SCL_SECURE_NO_DEPRECATE /D_SECURE_SCL=0 /DMATLAB_MEX_FILE /nologo /MD /FoC:\Users\STOCKE~1.IT1\AppData\Local\Temp\1\mex_8gw18h\mex_file_sonar.obj -I"C:\Program Files\MATLAB\R2013b\extern\include" -I"C:\Program Files\MATLAB\R2013b\simulink\include" /O2 /Oy- /DNDEBUG -DMX_COMPAT_32 mex_file_sonar.cpp

mex_file_sonar.cpp Contents of C:\Users\STOCKE~1.IT1\AppData\Local\Temp\1\mex_8gw18h\mex_tmp.rsp: C:\Users\STOCKE~1.IT1\AppData\Local\Temp\1\mex_8gw18h\mex_file_sonar.obj

--> link /out:"mex_file_sonar.mexw64" /dll /export:mexFunction /LIBPATH:"C:\Program Files\MATLAB\R2013b\extern\lib\win64\microsoft" libmx.lib libmex.lib libmat.lib /MACHINE:X64 kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib /nologo /manifest /incremental:NO /implib:"C:\Users\STOCKE~1.IT1\AppData\Local\Temp\1\mex_8gw18h\templib.x" /MAP:"mex_file_sonar.mexw64.map" @C:\Users\STOCKE~1.IT1\AppData\Local\Temp\1\mex_8gw18h\mex_tmp.rsp C:\home\stockel\matlab\mex\blueview\bvtsdk3.lib

   Creating library C:\Users\STOCKE~1.IT1\AppData\Local\Temp\1\mex_8gw18h\templib.x and object C:\Users\STOCKE~1.IT1\AppData\Local\Temp\1\mex_8gw18h\templib.exp 
mex_file_sonar.obj : error LNK2019: unresolved external symbol __imp_BVTSonar_Destroy referenced in function mexFunction 
mex_file_sonar.obj : error LNK2019: unresolved external symbol __imp_BVTPing_Destroy referenced in function mexFunction

... lines deleted for brevity ...

mex_file_sonar.mexw64 : fatal error LNK1120: 23 unresolved externals

C:\PROGRA~1\MATLAB\R2013B\BIN\MEX.PL: Error: Link of 'mex_file_sonar.mexw64' failed.

Unable to complete successfully.

Error in bvCompile (line 14) mex('-v', iPath, '-lbvtsdk3', lPath, 'mex_file_sonar.cpp');

--------------- end mex output ----------------------

I have used the DUMPBIN utility on the .lib file to make sure the symbols are present, with output:

---------- DUMPBIN output -------------------------

File Type: LIBRARY

     Exports

       ordinal    name
                  _BVTSonar_Destroy
                 _BVTPing_Destroy

... lines deleted for brevity

-------------- end DUMPBIN output ---------------------

So the library contains the symbols. Why do I have unresolved references?

Thanks, Jim

[Ken Atwell]

The linker error concerns symbols:

 *__imp_BVTSonar_Destroy
 *__imp_BVTPing_Destroy

Not

 * _BVTSonar_Destroy
 * _BVTPing_Destroy

You deleted some lines for brevity, so does the DUMPBIN output also contains the "__imp" symbols?

[Jim Stockel]

The DUMPBIN output does not contain any "_imp" sysmbols. I noticed this, but am not familiar enough with the link process to know whether the "_BVT" symbols would satisfy the "_imp_BVT" symbols. Apparently not. Is this some library incompatability?

[Jim Stockel]

Based on the recommendation of the producer of the commercial library I am using, I will try to do this using the capabilities of matlab to directly access the libarary using loadlib and related functions. Thanks to those who attempted to help.