Andrew Kesterson
5eaa956f50
An unhandled error could kill the process and still report success. The default handler ended in exit(errctx->status), and an exit status is one byte wide: the kernel keeps the low 8 bits of the argument and discards the rest. Consumer statuses start at AKERR_FIRST_CONSUMER_STATUS (256), so the first status any consumer can reserve exited 0 and a shell saw a clean run. Status 300 exited 44, an unrelated error's code. There is no wider exit() to reach for. _exit(), _Exit(), quick_exit() and the raw exit_group syscall all truncate identically, and even waitid(), whose si_status is a full int, reports the truncated value -- the truncation happened before the parent looked. akerr_exit() now owns that mapping and the default handler calls it: 0 exits 0, 1 through 255 exit the status, and anything else exits AKERR_EXIT_STATUS_UNREPRESENTABLE (125) rather than a low byte that is either a lie or a claim of success. Only values that were already being delivered wrong behave differently. Call it instead of exit() anywhere you leave the process on a status; it is declared AKERR_NORETURN. akerr_exit(0) exits 0, because 0 is this library's success status. That is not a hole in the rule: PROCESS opens with case 0, which marks a zero status handled, so a successful context never reaches FINISH_NORETURN's call to the handler at all. tests/err_exit_status.c drives one table through akerr_exit() and through the default handler in forked children and requires identical exit codes, so the handler cannot grow a mapping of its own. With the clamp removed it fails with "akerr_exit(256) exited 0, want 125". The full-width status was already reaching the log and still does, which the same test asserts against the captured stack trace. 2.0.1. No ABI break: the soname stays libakerror.so.2 and nothing that already existed changed shape. akerr_exit() is a new exported symbol, so a consumer that starts calling it needs 2.0.1 at link time. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
6.9 KiB
6.9 KiB