"TypeError: Module.X is not a constructor" while creating C++ object in javascript code after compilation with intermediate bitcode state

[Pawel]

Hello All,

I get a TypeError: Module.ClassA is not a constructor error while creating object.

I'm having a simple header class defined in header class_a.h:

namespace MyNamespace

{

  class ClassA

  {

  public:

    ClassA();

    void PrintName();

  };

}

and its implemetation in class_a.cpp

#include <iostream>

#include "class_a.h"

namespace MyNamespace

{

  ClassA::ClassA()

  {

    std::cout << "MyNamespace::ClassA constructor" << std::endl;

  }

  void ClassA::PrintName()

  {

    std::cout << "MyNamespace::ClassA::PrintName method" << std::endl;

  }

}

I described in interface in class_a.idl:

[Prefix="MyNamespace::"]

interface ClassA

{

  void ClassA();

  void PrintName();

};

Next I create glue files with:

python ${EMSCRIPTEN_ROOT}/tools/webidl_binder.py class_a.idl class_a_glue

And glue_wrapper.cpp containing

#include "class_a.h"

#include "class_a_glue.cpp"

Now I'd like to create bitcode

em++ class_a.cpp glue_wrapper.cpp --post-js class_a_glue.js -o class_a.bc

and finally the javascript

em++ class_a.bc -o class_a.js

Up to now everything works fine, neither error nor warning reported.

I define simle client.js script creating object and calling method:

var obj = new Module.ClassA();

obj.PrintName();

When I load both class_a.jd and client.js scripts in html I get

client.js:1 Uncaught TypeError: Module.ClassA is not a constructor at client.js:1

The interesting is that, if I create javascript in one step (without intermediate .bc) then it works fine - I see proper printouts in browser console.

I'm however not likely going this way because I've got a bunch of classes I'd like to put into one javascript, e.g.

em++ class_a.cpp glue_wrapper.cpp --post-js class_a_glue.js -o class_a.bc

em++ class_b.cpp b_glue_wrapper.cpp --post-js class_b_glue.js -o class_b.bc

em++ class_c.cpp c_glue_wrapper.cpp --post-js class_c_glue.js -o class_c.bc

...

em++ class_a.bc class_b.bc class_c.bc ... -o class_a.js.

I'm using:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 1.35.23

clang version 3.9.0  (emscripten 1.35.23 : 1.35.23)

Why it does not work with intermediate bitcode step? Or maybe my approach is incorrect?

Best regards, Paweł

[Thomas Lively]

Hi Pawel,

I notice that the emscripten version you’re using is quite old. Can you reproduce the issue with the latest version?

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[Pawel]

Hi Thomas,

I reproduce it using version 1.36.14.

I cannot use newer versions (>=1.37.0) yet due to required dependencies I'm obligated not to use in my project.

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[Enkidu Zero]

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-------- ข้อความต้นฉบับ --------
เรื่อง: Re: "TypeError: Module.X is not a constructor" while creating C++ object in javascript code after compilation with intermediate bitcode state
จาก: Pawel
ถึง: emscripten-discuss
สำเนา:

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[Pawel]

I've reproduced the issue on separated Ubuntu 19.04 environment using latest available components:

emscripten-1.38.31

clang-e1.38.31-64bit

node-12.9.1-64bit

Is it a bug or my workflow is wrong?