0e9b3215

fix: the coverage shim runs the word that forks bare, not every start

a73x 2026-08-30 10:11

Commit message

fix: the coverage shim runs the word that forks bare, not every start

`run` became `start`, and the shim's `start|endpoint) exec bare` — written
when `start` was only the launcher — swallowed every foreground daemon the
suite runs. `make coverage` went green measuring no daemon at all:
server.zig 0/819 lines, quic_server.zig 0/276.

The word that daemonises is `-d`, and it is now a word in one slot, so the
shim can read it exactly. Detached launchers stay bare; the plain
`mux d start` a scenario runs in the foreground is traced again — 373/819
and 225/276 over E2E_ONLY=01_boot alone.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017wi2HnuF1EK8HgViU11YLV

test/coverage.sh

Old		New
@@ -22,18 +22,22 @@
22	# the one signal a wrapper cannot forward, so a leg that kill -9s a	22	# the one signal a wrapper cannot forward, so a leg that kill -9s a
23	# daemon would leave the real one alive holding its socket. e2e.sh's	23	# daemon would leave the real one alive holding its socket. e2e.sh's
24	# hardkill answers that; see the comment there.	24	# hardkill answers that; see the comment there.
25	# - kcov waits for the LAST traced descendant, and `mux d start -d` daemonises:	25	# - kcov waits for the LAST traced descendant, and `mux d start -d`
26	# its launcher forks, the parent exits, and the daemon reparents to init.	26	# daemonises: the launcher forks, the parent exits, and the daemon
27	# Traced, that daemon outlives the scenario, so kcov never exits and the	27	# reparents to init. Traced, that daemon outlives the scenario, so kcov
28	# suite's `wait` on it never returns — a hang at the auto-start leg that	28	# never exits and the suite's `wait` on it never returns — a hang at the
29	# reads as a slow run, and one that ignores SIGTERM, so `timeout` will not	29	# auto-start leg that reads as a slow run, and one that ignores SIGTERM,
30	# free it either. The shims therefore run `start` BARE, exporting	30	# so `timeout` will not free it either. So the shim reads the WORD that
31	# MUX_KCOV_ACTIVE so the `mux d start -d` it re-execs stays bare too. The cost	31	# forks: `mux d start -d` runs bare, and the plain `mux d start` a
32	# is the auto-started daemons' lines; the alternative was a suite that	32	# scenario runs in the foreground is traced like anything else. That is
33	# could not finish. `endpoint` is the same shape one hop out: it spawns	33	# where server.zig's e2e lines come from, and widening the case back to
34	# the daemon it announces, and the ssh handoff client then kill()s its	34	# every `start` loses all of them for a gate that still goes green;
35	# ssh child and WAITS on it — which under the shim is kcov, holding on	35	# narrowing it to every `start` hangs the suite at the first `-d` leg.
36	# for that daemon. The handoff legs stalled there with attaches=0.	36	# The cost is the detached daemons' lines. `endpoint` is the same shape
		37	# one hop out and stays bare whole: it spawns the daemon it announces,
		38	# and the ssh handoff client then kill()s its ssh child and WAITS on it
		39	# — which under the shim is kcov, holding on for that daemon. The
		40	# handoff legs stalled there with attaches=0.
37	#	41	#
38	# Not --exit-first-process, which is kcov's own answer to daemons: it	42	# Not --exit-first-process, which is kcov's own answer to daemons: it
39	# reparents the tracer, and then the real process is no longer a CHILD of	43	# reparents the tracer, and then the real process is no longer a CHILD of
@@ -114,7 +118,10 @@ cat > "$SHIM/mux" <<SHIM_EOF
114	[ -n "\$MUX_KCOV_ACTIVE" ] && exec "$real" "\$@"	118	[ -n "\$MUX_KCOV_ACTIVE" ] && exec "$real" "\$@"
115	case "\${1:-}" in d\|a\|web) _m=\$1; _v=\${2:-} ;; *) _m=: ; _v=\${1:-} ;; esac	119	case "\${1:-}" in d\|a\|web) _m=\$1; _v=\${2:-} ;; *) _m=: ; _v=\${1:-} ;; esac
116	case " $TRACED " in " \$_m ") ;; *) exec "$real" "\$@" ;; esac	120	case " $TRACED " in " \$_m ") ;; *) exec "$real" "\$@" ;; esac
117	case "\$_v" in start\|endpoint) exec "$real" "\$@" ;; esac	121	case "\$_m \$_v" in
		122	"d endpoint") exec "$real" "\$@" ;;
		123	"d start") case "\${3:-}" in -d\|--detach) exec "$real" "\$@" ;; esac ;;
		124	esac
118	MUX_KCOV_ACTIVE=1; export MUX_KCOV_ACTIVE	125	MUX_KCOV_ACTIVE=1; export MUX_KCOV_ACTIVE
119	exec kcov --collect-only "--include-path=$SRC" "$RAW/mux.\$\$" "$real" "\$@"	126	exec kcov --collect-only "--include-path=$SRC" "$RAW/mux.\$\$" "$real" "\$@"
120	SHIM_EOF	127	SHIM_EOF