# CFMachPortCreateWithPort(_:_:_:_:_:) Creates a CFMachPort object for a pre-existing native Mach port. ``` func CFMachPortCreateWithPort(_ allocator: CFAllocator!, _ portNum: mach_port_t, _ callout: CFMachPortCallBack!, _ context: UnsafeMutablePointer!, _ shouldFreeInfo: UnsafeMutablePointer!) -> CFMachPort! ``` ## Parameters `allocator` The allocator to use to allocate memory for the new object. Pass `NULL` or [`kCFAllocatorDefault`](/documentation/CoreFoundation/kCFAllocatorDefault) to use the current default allocator. `portNum` The native Mach port to use. `callout` The callback function invoked when a message is received on the Mach port. `context` A structure holding contextual information for the Mach port. The function copies the information out of the structure, so the memory pointed to by `context` does not need to persist beyond the function call. `shouldFreeInfo` A flag set by the function to indicate whether the `info` member of `context` should be freed. The flag is set to `true` on failure or if a CFMachPort object already exists for `portNum`, `false` otherwise. `shouldFreeInfo` can be `NULL`. ## Return Value The new CFMachPort object or `NULL` on failure. If a CFMachPort object already exists for `portNum`, the function returns the pre-existing object instead of creating a new object; the `context` and `callout` parameters are ignored in this case. Ownership follows the [The Create Rule](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html#//apple_ref/doc/uid/20001148-103029). ## Discussion The CFMachPort object does not take full ownership of the send and receive rights of the Mach port `portNum`. It is the caller’s responsibility to deallocate the Mach port rights after the CFMachPort object is no longer needed and has been invalidated. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)