Unsolved external symbol in C++ interface build

I have a C++ function which I can load on MATLAB with

loadlibrary('nc_driver_x64')

and this works without problem using calllib.

On the other hand, if I try to create interface of the same function like this

clibgen.generateLibraryDefinition(fullfile(workPath,'nc_driver_x64.h'),...
    "IncludePath", workPath,... 
    "Libraries", {fullfile(workPath,'nc_driver_x64.lib'), fullfile(workPath,'nc_driver_x64.dll')},...
    "Verbose",true)

It generates definenc_driver_x64.m and definenc_driver_x64.mlx, but then

build(definenc_driver_x64)

returns nc_driver_x64Interface.obj : error LNK2019: on all functions in this file.

.h, .lib and .dll files are all in the same folder and running on R2021b

I really appreciate if you could point out what I should check to make this work!

Answer 1

[Madheswaran]

Hi @Hiroyuki Kobayashi

I think the problem you are facing is because of a compiler mismatch between the one used to build your C++ library and the one MATLAB is using to build the interface. Since your library works fine with "loadlibrary" and "calllib", but fails during the "build(definenc_driver_x64)" step with LNK2019 errors (unresolved external symbols), this suggests the interface building process is using a different compiler than what was used to create your original library.

To solve this, you should check which compiler was used to build your original "nc_driver_x64" library and make sure MATLAB is using the same compiler when building the interface.

The list of suitable and compatible compilers is listed here: https://www.mathworks.com/support/requirements/supported-compilers.html

You can check your current MATLAB C++ compiler setting with:

mex -setup cpp

This will show you which compiler MATLAB is currently using. You can find more information here: https://www.mathworks.com/help/matlab/ref/generatecinterface.html

If the compiler MATLAB currenlty using doesn't match the compiler used for your library, you'll need to either:

1. Change your MATLAB compiler setting to match the one used for your library (if you have that compiler installed)
2. Or rebuild your library using the compiler that MATLAB is currently set to use

You can also find possible trouble shooting steps to resolve build errors here: https://www.mathworks.com/help/matlab/matlab_external/resolve-build-error-unresolved-external-symbols.html

Hope this helps!