I performed a check of the Qt code using the PVS-Studio static code analyzer and extracted 96 warnings which in my opinion point at real errors in code. I described found defects in the article "A Third Check of Qt 5 with PVS-Studio" - https://www.viva64.com/en/b/0584/

Most likely, there are more errors in total. We are ready to give a temporary license so that Qt authors could thoroughly check their code. If you're interested, please, write to our support.