message(STATUS) prints output to a buffered stdout, whereas message(NOTICE) or just message() print to unbuffered stderr. We use a mix of message() calls when printing the configuration summary, which caused interleaved output. Because CMake offers no message(FLUSH), we work around the issue by calling execute_process(COMMAND -E echo " ") which does call std::cout << s << std::flush; We seem to have to do it twice, before and after the detailed configuration summary is printed. Pick-to: 6.2 6.3 Change-Id: Ibc075551fc0547073f0696477e54d9b9c1edca97 Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>