From the attached backtrace, It seems that Qt calls FcInitReinitialize when populating its font database (a QGenericUnixFontDatabase instance provided by Qtubuntu) - that explains why re-parses the conf files everytime.
See http://code.qt.io/cgit/qt/qtbase.git/tree/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp?h=v5.4.1#n439
From the attached backtrace, It seems that Qt calls FcInitReinitialize when populating its font database (a QGenericUnixFon tDatabase instance provided by Qtubuntu) - that explains why re-parses the conf files everytime.
See http:// code.qt. io/cgit/ qt/qtbase. git/tree/ src/platformsup port/fontdataba ses/fontconfig/ qfontconfigdata base.cpp? h=v5.4. 1#n439