Why do I get "identifier is undefined" and "expected an expression" errors when using the Simulink Code Importer tool?

I am trying to import code using the Simulink Code Importer tool, or its graphical wizard, documented here:

https://www.mathworks.com/help/releases/R2023a/simulink/code-importer.html

https://www.mathworks.com/help/releases/R2023a/simulink/ug/import-custom-code-using-the-simulink-code-importer-wizard.html

When doing so, I get errors that look like the following:

Failed to parse custom code.
Caused by:
"/path/to/my_header.h", line L: error: identifier "namespace" is undefined
| namespace my_ns {
| ^
"/path/to/my_header.h", line L: error: expected a ";"
| namespace my_ns {
| ^
"/path/to/my_impl", line M: error: identifier "using" is undefined
| using foo = my_template<baz>;
| ^
"/path/to/my_impl", line M: error: identifier "my_template" is undefined
| using foo = my_template<baz>;
| ^
"/path/to/my_impl", line M: error: expected an expression
| using foo = my_template<baz>;
| ^
"/path/to/my_impl", line N: error: expected a ";"
| template
Why is this happening? I know the code is valid, I can compile it manually without any issues.

Answer 1

[MathWorks Support Team]

The code shown in these errors indicates that the custom code you are providing was written in C++, but the default option for the Code Importer tool is to parse files as C code. When providing your source and header files to the Code Importer, you also need to change the language to C++.

If you are using the command-line interface, set the "CustomCode.Language" property of your "CodeImporter" object to "C++". If you are using the graphical wizard, once you get to the "Specify Custom Code" step, change the "Language" option to "C++".