Thank you very much for the quick reply!
But what about using only glibc functions like set/getxattr and removexattr? Would it be an appropriated solution? The only target platform is Linux, if it matters.
BTW, the solution with g_file_info_remove_attribute/g_file_set_attributes_from_info probably would not work. Though the attribute is removed from the GFileInfo structure, but then, when we write the structure back to the disk, the removed attribute seems to be kept untouched there.