Although the specific cause -- (mode_t)-1 -- is something that you can't really do in many languages. So you'd likely have to write 0777 or equivalent explicitly down, making it so much more obvious what a bad idea that is.
The 'fixed' code¹ has the property that calling it to create a file with mode==0 (i.e. no permissions) actually creates one with mode==0644 (i.e. some permissions), which is a wtf r u doin that can't be blamed on C.
¹ https://github.com/systemd/systemd/commit/06eeacb6fe029804f2...