Question
I have a C++ DLL and its header file. I'm trying to build a MEX function for each function in the DLL, and one of the functions has the following signature: % // This is from the C++ header file int myFunc( const char * const Input1, SomeStructType * Output1, int & Output2); { ... } When I try to build a MEX in defining the inputs in my MATLAB workspace and then I run this command: myFuncReturnValue = coder.ceval('myFunc', coder.ref(Input1), coder.ref(Output1), ***???***) The error i get is: ...error C2664: 'int myFunc( const char * const Input1, SomeStructType * Output1, int & Output2)': cannot convert argument 3 from 'int16_t' to 'int &'... I couldn't find any help defining 'int &' as a MATLAB datatype so i can't pass it into the MEX builder.
Expert Answer
Kshitij Singh
PhD Expert
Answered Aug 25, 2026
Unfortunately, calling a C++ function that has a reference parameter in its signature is not supported in MATLAB Coder as of MATLAB R2020b. We've made an internal note of your request so we can look at lifting that limitation in the future. Meanwhile, as a workaround, the best you can do is to create a wrapper C++ function that takes a pointer, which in turn calls the function that takes the reference, as I've shown in the following simple example:
myFunc.hpp
int myFunc(int& out);
myFunc.cpp
#include "myFunc.hpp"
int myFunc(int& out)
{
out = 2;
return 5;
}
myFuncWrapper.hpp
#include "myFunc.hpp"
inline int myFuncWrapper(int* out) {
return myFunc(*out);
};
callMyFuncWrapper.m
function y = callMyFuncWrapper %#codegen
y = int32(0);
if coder.target('MATLAB')
% Executing in MATLAB, call MATLAB equivalent of
% C function myFuncWrapper
y = int32(5 + 2);
else
% Executing in generated code, call C function myFuncWrapper
coder.updateBuildInfo('addSourceFiles','myFunc.cpp');
coder.cinclude('myFuncWrapper.hpp');
in = int32(0);
y = coder.ceval('myFuncWrapper', coder.ref(in));
y = y + in;
end
end
Call codegen
>> codegen callMyFuncWrapper -report -lang:c++
100% Run Guarantee
3-Hour Fast-Track Delivery
Need a Custom Version or Complete Simulation for This Problem?
Our 500+ PhD engineers build, debug, and optimize working MATLAB scripts and Simulink (.slx) models tailored to your exact assignment rubrics with zero plagiarism.
Tested on MATLAB R2024b / R2026a
Turnitin 0% Plagiarism Report
Free 7-Day Revisions Guarantee
Have a different question? Ask here
Related matlab Questions & Solutions
Browse All →
Explore similar technical troubleshooting questions and verified MATLAB solutions:
Ready-to-Run MATLAB & Simulink Projects
Browse All Projects →