/usr/include/sigc++-2.0/sigc++/adaptors/ is in libsigc++-2.0-dev 2.4.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/sigc++-2.0/sigc++/adaptors/adaptor_trait.h
/usr/include/sigc++-2.0/sigc++/adaptors/adaptors.h
/usr/include/sigc++-2.0/sigc++/adaptors/bind.h
/usr/include/sigc++-2.0/sigc++/adaptors/bind_return.h
/usr/include/sigc++-2.0/sigc++/adaptors/bound_argument.h
/usr/include/sigc++-2.0/sigc++/adaptors/compose.h
/usr/include/sigc++-2.0/sigc++/adaptors/deduce_result_type.h
/usr/include/sigc++-2.0/sigc++/adaptors/exception_catch.h
/usr/include/sigc++-2.0/sigc++/adaptors/hide.h
/usr/include/sigc++-2.0/sigc++/adaptors/lambda/
/usr/include/sigc++-2.0/sigc++/adaptors/lambda/base.h
/usr/include/sigc++-2.0/sigc++/adaptors/lambda/group.h
/usr/include/sigc++-2.0/sigc++/adaptors/lambda/lambda.h
/usr/include/sigc++-2.0/sigc++/adaptors/lambda/operator.h
/usr/include/sigc++-2.0/sigc++/adaptors/lambda/select.h
/usr/include/sigc++-2.0/sigc++/adaptors/retype.h
/usr/include/sigc++-2.0/sigc++/adaptors/retype_return.h
/usr/include/sigc++-2.0/sigc++/adaptors/track_obj.h