C++ Call Matlab error

While executing a C++ function called by Matlab I want to report errors back to Matlab. In the C mex API there is mexErrMsgTxt, but I haven't found any corresponding C++ calls. Tried using this helper function

void mxErrorMessage(std::string msg)
{
    auto args = factory.createCharArray(msg);
    matlabPtr->feval(u"error", args);
}

but I get the following error when I force it to be called

Error using error
Too many output arguments.

Is there a more Matlab appropriate solution that I am missing? Why am I getting this error?

[Rik]

I have no experience with C++, but the Matlab error sounds like C++ expects the error function to return an output, which it doesn't.

[kameranis]

That's also how I read it, but looking at the ceval documentation I don't understand how it should be written. The only thing I can imagine is that

matlabPtr->feval(u"error", args);

is an expression and therefore it needs to have a rvalue. This still does not explain how I should be writing this.

Answer 1

[Rik]

The way I read the documentation page you linked, you need to do this:

    // Call function with no output by using void as the type
    matlabPtr->feval<void>(u"error", args);

[kameranis]

Thank you for pointing this out. In the past few days I have been experimenting with getting this to work but it seems I am still missing something. I changed the data type of args from auto to a proper type, but it stills refuses to work.

void mxErrorMessage(std::string msg)
{
    matlab::data::CharArray args = factory.createCharArray(msg.data());
    matlabPtr->feval<void>(u"error", args);
}

The errors from mex can be found here.

It seems to be some sort of type mismatch, but I can't figure it out.