Why do I receive errors when building a model which contains an S-function with MAT-file API in Simulink?

I have a C-MEX S-function that I use to read data from a MAT-file. I use commands such as: matOpen, matGetVariable, in my C-code.

I also include the header file needed for using those functions, by using the command:

#include "mat.h"

When I build the model using Generic Real-Time target (grt.tl), I receive error messages during my build process.

For example:

C:\Apps\MATLAB\extern\include\matrix.h(144) : error C2371: 'mxArray' : redefinition; different basic types 
   C:\Apps\MATLAB\rtw\c\libsrc\rt_matrx.h(41) : see declaration of 'mxArray' 

Or with the Simulink Real-Time target (slrealtime.tlc):

C:\ProgramData\MATLAB\SupportPackages\R2021b\toolbox\slrealtime\target\supportpackage\qnx710\\host\win64\x86_64\usr\bin\x86_64-pc-nto-qnx7.1.0-ld: sfun_wrapper.o: in function `sfun_Outputs_wrapper(double const*, double*, double*, double*, double*, double*, double*)':
D:/data/sfun_wrapper.cpp:70: undefined reference to `matOpen_800'
D:/data/sfun_wrapper.cpp:78: undefined reference to `matGetVariable_800'
D:/data/sfun_wrapper.cpp:90: undefined reference to `mxGetFieldNumber_800'
D:/data/sfun_wrapper.cpp:95: undefined reference to `mxGetField_800'
D:/data/sfun_wrapper.cpp:96: undefined reference to `mxGetPr_800'
D:/data/sfun_wrapper.cpp:97: undefined reference to `mxGetM_800'
D:/data/sfun_wrapper.cpp:165: undefined reference to `mxDestroyArray_800'
D:/data/sfun_wrapper.cpp:166: undefined reference to `matClose_800'
cc: C:/ProgramData/MATLAB/SupportPackages/R2021b/toolbox/slrealtime/target/supportpackage/qnx710//host/win64/x86_64/usr/bin/x86_64-pc-nto-qnx7.1.0-ld caught signal 1 sfun_mat.mk:235: recipe for target 'D:/data/MyModel_slrealtime_rtw/MyModel' failed

Answer 1

[MathWorks Support Team]

The ability to generate code from a model that has C MEX S-functions with MAT-file API functions is not available in Simulink Coder, Embedded Coder or Simulink Real-Time.

The MAT-file API relies on precompiled libraries that are only available for the host PC desktop platform (Windows, MacOS, Linux), and not for Embedded Targets.

https://www.mathworks.com/help/matlab/matlab_external/mat-file-library-and-include-files.html

The library source code is not available to users for re-compilation. There are no workarounds.