PATH environment variable is different in the Qt C++ code and process explorer tool

Question

I am trying to update the PATH environment variable inside my C++ program using Qt on Windows 10. There is something wired in this scenario that I cannot understand. The strange point is that the value of PATH environment variable is getting different in the C++ code and in process explorer tool after dynamically loading a Matlab .dll file (i.e. MatlabEngine.dll). Here is a simplified version of the code:

    QString new_path = getNewPath();
    bool res = qputenv("PATH", new_path.toStdString().c_str()); 
    assert(res);
    auto applied_path = qgetenv("PATH"); // Line X of the code: process explorer shows the same value for PATH environment variable as applied_path variable
    
    // load a Matlab .dll dynamically
    if (!oneMatlabDll.load())
    {
       throw someException;
    }
    
    applied_path = qgetenv("PATH"); // Line Y of the code: process explorer does not show the updated value of PATH environment variable as before. But, the applied_path variable is exactly the same as line X. 

Does anyone have any idea why the value of PATH environment variable retrieved by qgetenv() is different from the one showed by process explorer tool? Here are some thoughts:

• An issue with process explorer tool
• An issue with qgetenv() method
• Dynamically loading the .dll file runs some hidden code that causes this problem. (?)

Update 1: If I add this silly line of code after line Y, then the process explorer shows the same value as the output of qgetenv("PATH"):

qputenv("PATH", qgetenv("PATH")); // this line fixes the issue

Answer 1

I could not find any reason behind this problem. It seems that it can be an internal issues comes from Qt/Windows. So, the only workaround that I have found is to add the below line again:

qputenv("PATH", qgetenv("PATH")); // this line fixes the issue