Since the definition of the external function is defined in a C++ file, a C++ compiler will be used to build the object for that file.
By default, MATLAB Coder generates C code, and the generated C code will be calling into a C++ function. For C++ functions to be visible in C code, they must be exported with extern "C" attribute. The following is an example of this:
#ifndef _CPP_TEST_FN_H
#define _CPP_TEST_FN_H
#ifdef __cplusplus
extern "C" {
#endif
int mytestadd(int a, int c);
#ifdef __cplusplus
}
#endif
#endif
Alternatively, if you want the generated code in C++, you can use "-lang:C++" as an option to codegen command. In this case, the functions do not need to be exported using extern “C” attribute and generated code should successfully build.
