变量浮点C++函数在获取浮点数的参数时不起作用。

我有一个可变模板函数:

template<typename T, typename ArgType>
vector<T>
createVector(const int count, ...)
{
  vector<T> values;
  va_list vl;
  va_start(vl, count);
  for (int i=0; i < count; ++i)
  {
    T value = static_cast<T>(va_arg(vl, ArgType));
    values.push_back(value);
  }
  va_end(vl);
  return values;
}

这适用于T和argtype的某些(对我来说,很奇怪)配置,但不是我期望的那样:

// v1 = [0.0, 1.875, 0.0]
vector<float> v1 = createVector<float, float>(3, 1.0f, 2.0f, 3.0f);
// v2 = [0.0, 1.875, 0.0]
vector<float> v2 = createVector<float, float>(3, 1.0, 2.0, 3.0);
// v3 = [1.0, 2.0, 3.0]
vector<float> v3 = createVector<float, double>(3, 1.0, 2.0, 3.0);
// v4 = [1.0, 2.0, 3.0]
vector<float> v4 = createVector<float, double>(3, 1.0f, 2.0f, 3.0f);    
// v5 = [1.0, 2.0, 3.0]
vector<double> v5 = createVector<double, double>(3, 1.0, 2.0f, 3.0);  

当argtype是double(即使传递float)时,为什么这会起作用,而当它是float时,为什么不起作用?