MQ Timed With Monotonic Clock

POSIX message queue functions with CLOCK_MONOTONIC timeout support

The POSIX message queue functions mq_timedreceive() and mq_timedsend() are limited to CLOCK_REALTIME for their timeout parameter.

This repository provides two wrapper functions: mq_timedreceive_monotonic() and mq_timedsend_monotonic(), which use CLOCK_MONOTONIC instead.

The implementation is based primarily on poll().

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Integration test for realtime vs monotonic timeout behavior

This repository also includes an integration test that demonstrates the difference between:

• mq_timedreceive() using CLOCK_REALTIME
• mq_timedreceive_monotonic() using CLOCK_MONOTONIC

The test changes the Linux system wall clock while both modes are waiting, showing that:

• the mq_timedreceive() timeout is affected by wall-clock changes
• the mq_timedreceive_monotonic() timeout remains stable

See tests/integration/README.md for details about what the test verifies and how to run it.