Assign value to Chaiscript variable through user-type object gives unexpect behaviour

Question

I've got a peculiar problem with C++ and Chaiscript, hope somebody can help me with it, and I'll try to give it as much information as it is needed.

Basically, calling a c++ function defined in c++ through chaiscript, which returns a Vector2 object (user-type object), will return crazy values when I try to get a value directly from a member variable of Vector2 (x or y). If I assign the whole Vector2 to a variable, it will work as expected, and accessing the member variables will give me the expected value.

I managed to reproduce the problem with as minimum code as I could, getting rid of the physics engine and everything else I was using.

Here is the c++ code:

//test.cpp
#include <chaiscript/chaiscript.hpp>
#include <chaiscript/chaiscript_stdlib.hpp>

template<typename T>
struct Vector2
{
  Vector2() : x(0), y(0) {};
  Vector2(T px, T py) : x(px), y(py) {};
  Vector2(const Vector2& cp) : x(cp.x), y(cp.y) {};

  Vector2& operator+=(const Vector2& vec_r)
 {
  x += vec_r.x;
  y += vec_r.y;
  return *this;
 }

 Vector2 operator+(const Vector2& vec_r)
 {
  return Vector2(*this += vec_r);
 }

 void operator=(const Vector2& ver_r)
 {
  x = ver_r.x;
  y = ver_r.y;
 }


 T x;
 T y;
};

Vector2<float> GetValue()
{
    return Vector2<float>(10,15);
}

int main()
{
  chaiscript::ChaiScript _script(chaiscript::Std_Lib::library());

 //Registering stuff
 _script.add(chaiscript::user_type<Vector2<float>>(), "Vector2f");
 _script.add(chaiscript::constructor<Vector2<float> ()>(), "Vector2f");
 _script.add(chaiscript::constructor<Vector2<float> (float, float)>(), "Vector2f");
 _script.add(chaiscript::constructor<Vector2<float> (const Vector2<float>&)>(), "Vector2f");
 _script.add(chaiscript::fun(&Vector2<float>::x), "x");
 _script.add(chaiscript::fun(&Vector2<float>::y), "y");
 _script.add(chaiscript::fun(&Vector2<float>::operator +), "+");
 _script.add(chaiscript::fun(&Vector2<float>::operator +=), "+=");
 _script.add(chaiscript::fun(&Vector2<float>::operator =), "=");
 _script.add(chaiscript::fun(&GetValue), "getValue");

 _script.eval_file("test.chai");

 return 0;
}

And here is the script:

//test.chai
var test = 0.0
var test2 = Vector2f(10,10)


 test = getValue().x
 print(test)
 print(test2.x)

This code will reproduce the following: 6.52556e-38 10

This value from getValue().x (6.52556e-38) is actually different each time I run the code, but it will usually be some crazy value between 1.f~8.f that goes to exponential -36~-38.

I can get around this problem by using "var something = getValue()", and then accessing "something.x", but it would be helpful to understand why that happens and how I could get it fixed.

Answer 1

This is a bug in ChaiScript which has just been fixed on the develop branch and will be in the next release.

https://github.com/ChaiScript/ChaiScript/commit/4f972bcf67826591423149c006f80d43a026bd15