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MACH_MSG_SUCCESS
successful Mach message send or receive operation identifies a scoped API or runtime boundary rather than a general machine failure. MACH_MSG_SUCCESS is the zero result of mach_msg or a related messaging operation. It means the requested send, receive, or combined transaction completed at the IPC layer; the receiver must still validate the message identifier, size, descriptor layout, trailer, and semantic reply fields.
Where the result is produced
Several Apple low-level APIs use zero for success, but each typedef belongs to a distinct contract while evaluating successful Mach message send or receive operation. The return type, output validation, and resource ownership rules remain part of successful handling when diagnosing successful Mach message send or receive operation.
MACH_MSG_SUCCESS confirms IPC transport completion, not application-level acceptance of the message body. A server can receive a message successfully and then return a protocol-specific error in its reply. Keep the numeric value, declared return type, and first returning operation together with MACH_MSG_SUCCESS; the same integer can belong to a different status namespace in another API.
Evidence to preserve
| Capture | Diagnostic value |
|---|---|
| mach_msg options, send and receive sizes, timeout values, notify port, and the exact mach_msg_return_t. | Identifies the concrete object and operation associated with successful Mach message send or receive operation. |
| Message header bits, message ID, declared size, descriptor count, and complex-message flag. | Separates argument or lifecycle state from the provider beneath successful Mach message send or receive operation. |
| The disposition of every transferred port right and ownership of out-of-line memory. | Creates a stable before-and-after comparison for successful Mach message send or receive operation. |
| Receive buffer capacity, trailer format, reply-port identity, and the protocol version expected by the receiver. | Shows whether successful Mach message send or receive operation is the first result or a translated summary. |
For successful Mach message send or receive operation, preserve message header bits, message ID, declared size, descriptor count, and complex-message flag before reinstalling, rebooting, clearing state, or substituting another device or provider. A success observed only after such a change is useful comparison data for successful Mach message send or receive operation, but it does not identify the original cause.
A controlled diagnostic sequence
- Send a known protocol message and verify the receiver accepts its ID and descriptor schema after MACH_MSG_SUCCESS. Record the first returned status and any state transition observed during successful Mach message send or receive operation.
- Exercise a bounded timeout or deliberately undersized receive buffer to confirm those results are not decoded as success. Treat a changed result as a new boundary rather than automatic resolution of successful Mach message send or receive operation.
- Track transferred rights and out-of-line regions through destruction of the received message. Repeat the original supported operation so the check remains relevant to successful Mach message send or receive operation.
How nearby outcomes differ
| Observed comparison | Next conclusion to test |
|---|---|
| The first control changes the result | Concentrate on the variable isolated by this check: Send a known protocol message and verify the receiver accepts its ID and descriptor schema after MACH_MSG_SUCCESS. |
| The second comparison for successful Mach message send or receive operation reproduces the same first status | Preserve lower-layer provider, driver, service, or runtime evidence before editing application data. The second controlled check was: Exercise a bounded timeout or deliberately undersized receive buffer to confirm those results are not decoded as success. |
| A different status replaces successful Mach message send or receive operation after the bounded change | The operation moved to another boundary after the third controlled check. That check was: Track transferred rights and out-of-line regions through destruction of the received message. Retain both results and interpret the replacement through its own API contract for successful Mach message send or receive operation. |
Correction and proof
Targeted correction. Validate the received schema and ownership rules after transport success, and keep application reply errors separate from mach_msg_return_t handling. For successful Mach message send or receive operation, modify only the object, argument, policy, provider, or lifecycle state identified by the collected evidence.
Acceptance criterion. The send or receive returns MACH_MSG_SUCCESS, message framing passes protocol validation, transferred resources have one clear owner, and the expected application reply is processed separately. Re-run the original operation that produced successful Mach message send or receive operation under its original identity and supported configuration, then keep one negative control that still produces the expected neighboring outcome.
Technical references
These owner-maintained or standards-based sources define the namespace and subsystem contract needed to verify MACH_MSG_SUCCESS on the deployed platform version.
- Apple XNU: Mach message definitions — defines the status namespace used for successful Mach message send or receive operation.
- Apple: Mach overview — documents the API or lifecycle boundary behind successful Mach message send or receive operation.
- Apple XNU: kern_return_t definitions — provides ABI, implementation, or protocol context for successful Mach message send or receive operation.
- Apple XNU source repository — supports the portability and verification limits for successful Mach message send or receive operation.
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