Generating corresponding C++ interface class function signature inline behaviour for MATLAB classes not as expected?

Descriptions：

I would like to generate C++ classes for the MATLAB built-in object function poseGraph and its object functions, so that it is as easy to use poseGraph these object functions as in the stand-alone C++ environment. I have simply written a custom class slamPoseGraph to wrap poseGraph, and the entry parameters are all designed to be supported basic data types, the reference code is as follows:

classdef slamPoseGraph<handle
    properties (SetAccess = private, GetAccess = public)
        NumNodes
        NumEdges
        NumLoopClosureEdges
        LoopClosureEdgeIDs
        LandmarkNodeIDs
    end

    properties (Access=private)
        graph
    end

    methods
        function obj = slamPoseGraph(MaxNumEdges,MaxNumNodes)
            obj.graph = poseGraph('MaxNumEdges',MaxNumEdges,'MaxNumNodes',MaxNumNodes);

            obj.NumNodes = obj.graph.NumNodes;
            obj.NumEdges = obj.graph.NumEdges;
            obj.NumLoopClosureEdges = obj.graph.NumLoopClosureEdges;
            obj.LoopClosureEdgeIDs = obj.graph.LoopClosureEdgeIDs;
            obj.LandmarkNodeIDs = obj.graph.LandmarkNodeIDs;
        end

        function addRelativePose2D(obj,measurement,fromNodeID,toNodeID)
            infoMat = [1 0 0 1 0 1];
            addRelativePose(obj.graph,measurement,infoMat,fromNodeID,toNodeID);
        end

        function  optimizePoseGraph2D(obj)

            obj.graph = optimizePoseGraph(obj.graph);

            obj.NumNodes = obj.graph.NumNodes;
            obj.NumEdges = obj.graph.NumEdges;
            obj.NumLoopClosureEdges = obj.graph.NumLoopClosureEdges;
            obj.LoopClosureEdgeIDs = obj.graph.LoopClosureEdgeIDs;
            obj.LandmarkNodeIDs = obj.graph.LandmarkNodeIDs;
        end

        function measurements = nodeEstimates2D(obj)
            measurements = nodeEstimates(obj.graph);
        end

    end

end

I then wrote the entry-point function used to generate the C++:

function poses1= slamMapGraph2D(poseParams,measurement,fromID,toID)%#codegen
%% pose graph
pg = SlamGraph2D.slamPoseGraph(poseParams.MaxNumEdges,poseParams.MaxNumNodes);
pg.addRelativePose2D(measurement,fromID,toID);
pg.optimizePoseGraph2D();  
poses1 = pg.nodeEstimates2D();
end

C++ was successfully generated using the following command:

cfg = coder.config("lib","ecoder",true);
cfg.FilePartitionMethod = "MapMFileToCFile"; % It looks like you must set it up this way to ensure that the generated C++ interface(slamFactorGraph.h,slamFactorGraph.cpp) is not inlined. 
cfg.GenCodeOnly = true;
cfg.CppNamespace = "SlamGraph2D"; % or use package folder name
cfg.CppInterfaceStyle ="Methods";
cfg.TargetLang = 'C++';
cfg.CppInterfaceClassName = 'myGraph';

cfg.InlineBetweenUserFunctions = 'Readability'; 
cfg.InlineBetweenUserAndMathWorksFunctions = 'Readability';
cfg.InlineBetweenMathWorksFunctions = 'Speed';

poseParams.MaxNumEdges = 10000;
poseParams.MaxNumNodes = 5000;
measurement = [1,2,3];
fromID = 1;
toID= 2;

codegen -config cfg slamMapGraph2D -args {poseParams,measurement,fromID,toID} -report

However the corresponding C++ interface class signature was generated as follows:

class slamPoseGraph {
public:
  slamPoseGraph *init(double MaxNumEdges, double MaxNumNodes);
  void addRelativePose2D(const double measurement[3], double fromNodeID,
                         double toNodeID);
  void optimizePoseGraph2D(myGraph *aInstancePtr,
                           coder::robotics::core::internal::BlockMatrix &iobj_0,
                           coder::poseGraph &iobj_1);
  void nodeEstimates2D(::coder::array<double, 2U> &measurements) const;
  coder::poseGraph _pobj0;

private:
  coder::poseGraph *graph;
};

It is clear that inline behaviour occurs with the input parameters of the member function optimizePoseGraph2D (even when I add coder.inline("never") to the entry-point function slamMapGraph2D), which carries over into the Mathworks internal code and is not user-friendly!

Expectations:

1. A C++ member function signature similar to the following should be generated:

void optimizePoseGraph2D();

I.e. consistent with MATLAB class member function optimizePoseGraph2D(), no input parameter inline behaviour introduced.

2. The slamPoseGraph.h,slamPoseGraph.cpp interface classes should be separate files when configured to generate a single file for all functions.

cfg.FilePartitionMethod = "singleFile";

Environment:

ubuntu 20.04

Matlab R2023a

Answer 1

[Denis Gurchenkov]

Hi cui,

I understand what you want to achieve. You want to generate C++ code for this MATLAB class, and get a reusable, stable interface for all the methods. This is not currently possilbe using MATLAB Coder. See, coder takes an entry point function (or a number of functions) and generates C/C++ code for those functions. It gives you no guarantees about the internals of those functions. In particular, if an entry-point function calls some other (non-entry-point) function, creates an instance of a class, etc - those details may not be fully preserved in the generated code. The functions can be specialized, their inputs can be dropped etc, for the sake of optimization.

And that preservation of prototypes is exactly what you want.

In other words, you need a feature that we have not shipped yet.

MATLAB Coder dev team is aware of this need and is working on a feature to translate a MATLAB class to a C++ class, exactly what you want. I passed your example to the dev team, so that they can take it as a use case.

If you are interested and you would want to offer your feedback, please reach out via the technical support channel, we'd be happy to chat more!

Thanks

Denis

[cui,xingxing]

@Denis Gurchenkov Thank you for your interest, and I am more than happy to communicate with you amongst yourselves! I have encountered many other C/C++ code generation problems, you can follow my questions in detail, such as the following recent problems I encountered.

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