this is only happen on QtCreator 4.11.0, if I run QtCreator 4.10.2, no issues.

Qt 5.14.1 is built from source, and QtCreator 4.11.0 and QtCreator 4.10.2 both built from source, but they are in different folder.

use Qt Creator 4.11.0 create a c++ project, it give following error, see attached file,

on Qt 4.10.2 no issues.

run 4.11.0 and 4.10.2 by both

export QT_LOGGING_RULES=qtc.clang*=true
export LIBCLANG_TIMING=1
./qtcreator

qt 4.11.0

ignoring nonexistent directory "...."
ignoring nonexistent directory ""
#include "..." search starts here:
#include <...> search starts here:

....

/usr/include/c++/8
/usr/include/x86_64-linux-gnu/c++/8
/usr/include/c++/8/backward
/usr/local/include
/usr/include/x86_64-linux-gnu
/usr/include

and qt 4.10.2

/usr/include/c++/8
/usr/include/x86_64-linux-gnu/c++/8
/usr/include/c++/8/backward
/usr/lib/gcc/x86_64-linux-gnu/8/include
{{ /usr/local/include}}
/usr/lib/gcc/x86_64-linux-gnu/8/include-fixed
{{ /usr/include/x86_64-linux-gnu}}
{{ /usr/include}}