Extends Phase 0's chdir/errno/strerror with the syscalls that ffi/pty
needs to drive a forkpty'd child: waitpid (with WIFEXITED / WEXITSTATUS
/ WIFSIGNALED / WTERMSIG decoders), read, write, close, kill.
Status-word macros are reproduced from glibc bits/waitstatus.h using
the LuaJIT `bit` library. M.waitpid returns a structured (kind, value)
rather than the raw status word — callers don't have to know the
encoding:
"exit", N — normal exit, N is exit code
"signal", N — killed by signal N
"other", raw — stopped/continued (Phase 1 doesn't trace those)
nil, err — syscall failure
M.read / M.write / M.close / M.kill mirror their syscall return shape
with errno-string surfacing on failure. Read uses a shared 4 KiB
buffer for the common case; larger reads allocate a fresh buffer.
Smoke covers the chdir regression (still works), all four status
decoders against known status words, pipe round-trip for read/write/
close, EOF -> ("", 0), invalid-fd close -> false, kill(self, 0)
success, kill(bogus, 0) failure.
waitpid is not exercised by the smoke (needs a real child); that
arrives with ffi/pty.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
marfrit
113f87125a