MAP_FIXED is dup2 for memory mappings, and it’s useful in exactly the same situations where dup2 is useful for file descriptors: when you want to perform a replace operation that atomically reassigns a resource identifier (memory range in the case of MAP_FIXED, or fd in the case of dup2) to refer to a new resource without the possibility of races where it might get reassigned to something else if you first released the old resource then attempted to regain it for the new resource. c - When would one use mmap MAP_FIXED? - Stack Overflow
