The accessing of QPlainTextEdit trigger craching of all program

When trying to access QPlainTextEdit in function

int __cdecl printf2(const char *format, ...)

{

...

ui->plaintext_5555->appendPlainText("aaaaaaa");

}

which is placed in the same file, but called only from external library => the crash is raise.

Otherwise I can access the plaintext control without a problem from any other place in this file, but never from this function????

My goal is to update QPlainTextEdit with new text each time when external function vanitygen(...) return new string in vanitygenplus.cpp file.

Update #1 [14:41, 05.01.2018]:

I just tested with QLabel (instead of QPlainTextEdit) and all works fine, so the problem is somehow in QPlainTextEdit control.

Update #2 [15:48, 05.01.2018]:

Not work and with QTextEdit control.

Update #3 [16:21, 05.01.2018]

Not work and with QTextBrowser control

Update #4 [18:00, 05.01.2018]

Not work and with QLabel if set Qt::TextSelectableByMouse or Qt::TextSelectableByKeyboard