compat.libaio

// Behavioral test: real kernel AIO submissions, not a link check.
//
// Three things can go wrong with this package and none of them is a missing
// symbol.
//
//   1. `struct iocb` is the KERNEL's structure, assembled by libaio.h out of
//      PADDED/PADDEDptr/PADDEDul macros chosen by endianness and word size. Get
//      that selection wrong and every field lands at the wrong offset — the
//      library still links, io_submit still returns 1, and the kernel writes
//      the wrong bytes to the wrong place. So the assertions read back what
//      actually hit the file.
//
//   2. The plain names `io_getevents` and `io_cancel` do not exist as ordinary
//      definitions upstream: the functions are called `io_getevents_0_4` /
//      `io_cancel_0_4` and publish the short names through
//      `.symver … @@LIBAIO_0.4`. Whether that survives into a consumer's link
//      is a linker behavior, so both are called here on purpose.
//
//   3. libaio does NOT use errno. Every wrapper returns `-errno` directly and
//      restores the caller's errno, which is the opposite of the convention
//      the surrounding POSIX calls follow. The error-path assertion pins that
//      down rather than assuming it.
// …