The problem with QLibrary, help me!

[dungsivn]

I created a small application to use the library:

// Test is a simple widget for testing
Test::Test( QWidget* parent): QWidget(parent)
{
         setupUi(this);
         QByteArray buffer;
         QLibrary mylib("kernel32);
         typedef int (*GetLocalInfo)( int Locale, int LcType, char* l, int chData);
 
         GetLocaleInfor myFunc = (GetLocaleInfo)mylib.resolve("GetLocaleInfoA");
 
         if(myFunc(0x400, 0x1003, Buffer.data(), 99) !=0)
         {
         int v1= 1;
         float b2= 2.0;
         QString str = "Hi everyone";
         QMessageBox::information(0, "Hello","Hello");
 
         //...
}

// Test is a simple widget for testing
Test::Test( QWidget* parent): QWidget(parent)
{
         setupUi(this);
         QByteArray buffer;
         QLibrary mylib("kernel32);
         typedef int (*GetLocalInfo)( int Locale, int LcType, char* l, int chData);

         GetLocaleInfor myFunc = (GetLocaleInfo)mylib.resolve("GetLocaleInfoA");

         if(myFunc(0x400, 0x1003, Buffer.data(), 99) !=0)
         {
         int v1= 1;
         float b2= 2.0;
         QString str = "Hi everyone";
         QMessageBox::information(0, "Hello","Hello");

         //...
}

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After the line "QString str = "Hi everyone";", the pointer "this" would be changed the address, I don't know why? If I replace QString by another Object( QTextEdit, QLineEdit...),
it also changed "this" pointer. After the application changed the address, it display a warnining means that .exe was modified... and stop.

Could you tell me that way not to change the address?
Thanks!