You may be off by a decade. malloc and free existed long before 1988. I can find evidence of it going back as far as 1979 with 7th Edition Unix: https://en.wikipedia.org/wiki/Version_7_Unix http://man.cat-v.org/unix_7th/3/malloc

Most of what was defined by POSIX already existed on common platforms, like SunOS, before it was formally standardized. SunOS 4.0 even had mmap in early 1988! (See https://archive.org/stream/bitsavers_sunsunos4.erenceManual1... )