Matlab 2020A Matlab Coder Use C style EmxArray Bug

Hi everyone,

I am having problems with the new MATLAB Coder app. Before Matlab 2020a, if your target code was C++, variable size output format was emxArray type. Since 2020a, it has been changed to coder::array type by default. But in the link below it says that if you still want your output variables to be in C format (emxArray) while your target is C++, go to Memory Tab and change the dynamic memory allocation interface to --> Use C style EmxArray. I am doing this but it still generates coder_array.h file and all input/outputs are in coder::array (C++) format. Is it a bug? Has anyone tried this before? I would be pleased if you tell me what I am missing. Thank you.

https://www.mathworks.com/help///coder/ug/use-dynamically-allocated-cpps-arrays-in-generated-function-interfaces.html

Answer 1

[Andy]

Hi dober dober,

Unfortunatly, it looks like this is a bug in our 2020A release of MATLAB Coder.

You can work around this by doing the following:

- Convert the Project into a script as described here: https://www.mathworks.com/help///coder/ug/generate-a-matlab-script-to-build-a-project.html

- In the app toolbar, click the action menu (in the top right corner), and then select Convert to script.

- Specify the script name and click Save.

- Open the script file in the editor, you should see a piece of code that looks something like this:

      %% Create configuration object of class 'coder.EmbeddedCodeConfig'.
      cfg = coder.config('lib','ecoder',true);
      cfg.GenerateReport = true;
      cfg.ReportPotentialDifferences = false;
      cfg.DynamicMemoryAllocationInterface = 'C++';   % <---- Edit this line to say 'C'
      cfg.TargetLang = 'C++';
      cfg.GenCodeOnly = true;
      cfg.TargetLangStandard = 'C++03 (ISO)';

- Edit the line that says "cfg.DynamicMemoryAllocationInterface = 'C++';" to say "cfg.DynamicMemoryAllocationInterface = 'C';

- Move this line so that it is after the line "cfg.TargetLang = 'C++';" The final result should look something like this:

      %% Create configuration object of class 'coder.EmbeddedCodeConfig'.
      cfg = coder.config('lib','ecoder',true);
      cfg.GenerateReport = true;
      cfg.ReportPotentialDifferences = false;
      cfg.TargetLang = 'C++';                       % <---- Swap these two lines
      cfg.DynamicMemoryAllocationInterface = 'C';   % <----
      cfg.GenCodeOnly = true;
      cfg.TargetLangStandard = 'C++03 (ISO)';

The bug seems the be the cfg.TargetLang = 'C++' will overwrite the configuration option cfg.DynamicMemoryAllocationInterface with its default value (e.g. C++).

I apoligize for the inconvenience. In future versions this should be resolved and we'll look into fixing this in an update.

Thanks for pointing this out,

-Andy