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Troubleshoot S-Function Build Upgrade for R2020b

My pre-R2020b model uses S-Functions. When I migrated my model to the current release, I see this S-Function related message in the build log:

undefined reference to 'C function in S-Function'

What This Issue Means

In R2020b, the compiler for model builds changed from a Windows® compatible C compiler to the QNX® Neutrino® C++ compiler. To accommodate this change, update S-Function code for C++ compatibility.

Tip

Fortran S-Functions are not supported in R2020b and later releases of Simulink® Real-Time™.

Try This Workaround

To update S-Function code for C++ compatibility, modify the declaration of the S-Function in the header file.

For example, update this C S-Function declaration:

void getAllDataMyFunction(short);
void myfunction_initialize(short, unsigned char*, short*);
void myfunction_terminate(short, int);

Updated the code to this C++ S-Function declaration:

#ifdef __cplusplus
extern "C" {
#endif

void getAllDataMyFunction(short);
void myfunction_initialize(short, unsigned char*, short*);
void myfunction_terminate(short, int);

#ifdef __cplusplus
}
#endif

Before building the updated code, remember to remove all artifacts from previous model builds.

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