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refactor(airc): _reexec_into helper consolidates 5 exec sites (#205 target 1, net -21) #206

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Merged
joelteply merged 1 commit into from
Apr 28, 2026
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refactor(airc): _reexec_into helper consolidates 5 exec sites (#205 target 1, net -21) #206

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71 changes: 25 additions & 46 deletions airc
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Original file line number Diff line number Diff line change
Expand Up @@ -292,20 +292,22 @@ unset _gh_resolved

AIRC_WRITE_DIR="$(detect_scope)"

# Write a sentinel marker before any intentional `exec env ... "$0" ...`
# call, so the Windows daemon launcher .bat can distinguish "intentional
# re-exec into different mode" from "actual crash" (#203). On Linux/Mac
# `exec` is a true execve — the parent bash's PID becomes the new
# program, so the launcher script never observes an exit and the marker
# is harmless. On Windows MSYS-bash, exec is emulated as spawn-and-exit:
# the original bash exits + a new airc bash takes over. The launcher
# .bat sees the original bash exit, would normally treat it as a crash,
# and respawn — racing the new airc that just took over (Joel/continuum-
# b69f's #203 crashloop). Marker contents: "PID:UNIX_TIMESTAMP". Caller
# is responsible for invoking this immediately before exec.
_write_reexec_marker() {
local marker="$AIRC_WRITE_DIR/airc.reexec-marker"
printf '%d:%d\n' "$$" "$(date +%s)" > "$marker" 2>/dev/null || true
# Re-exec airc connect into a different mode (rejoin into another tab's
# gist or take over as host). Centralizes (a) the sentinel marker for
# the Windows daemon launcher (#203/#204 — distinguishes intentional
# re-exec from "actual crash"), (b) AIRC_NAME preservation across the
# exec, and (c) AIRC_NO_DISCOVERY=1 for host-takeover so the new
# instance won't re-find the just-deleted gist via gh's list-cache.
# Replaces 5 duplicated 3-line call sites in cmd_connect (#205 target 1).
_reexec_into() {
local mode="$1"; shift # "rejoin" or "host"
printf '%d:%d\n' "$$" "$(date +%s)" > "$AIRC_WRITE_DIR/airc.reexec-marker" 2>/dev/null || true
local _name; _name=$(get_config_val name "")
if [ "$mode" = "host" ]; then
exec env AIRC_NO_DISCOVERY=1 ${_name:+AIRC_NAME="$_name"} "$0" connect "$@"
else
exec env ${_name:+AIRC_NAME="$_name"} "$0" connect "$@"
fi
Comment on lines +306 to +310
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Copilot AI Apr 28, 2026

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_reexec_into passes AIRC_NAME to env via an unquoted parameter expansion. If the configured name ever contains whitespace/shell metacharacters, this will split into multiple args (the embedded quotes in AIRC_NAME="$_name" are literal characters and do not prevent word-splitting). Build an env argv array (as done in spawn_general_sidecar_if_wanted) and exec env "${env_args[@]}" ... to make this quoting-safe.

Suggested change
if [ "$mode" = "host" ]; then
exec env AIRC_NO_DISCOVERY=1 ${_name:+AIRC_NAME="$_name"} "$0" connect "$@"
else
exec env ${_name:+AIRC_NAME="$_name"} "$0" connect "$@"
fi
local -a env_args=()
if [ "$mode" = "host" ]; then
env_args+=(AIRC_NO_DISCOVERY=1)
fi
if [ -n "$_name" ]; then
env_args+=("AIRC_NAME=$_name")
fi
exec env "${env_args[@]}" "$0" connect "$@"

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Comment on lines +303 to +310
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Copilot AI Apr 28, 2026

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_reexec_into silently treats any mode other than host as the rejoin path. Since the function contract/comment says mode is rejoin|host, consider validating mode (including missing $1) and failing fast on unexpected values to avoid accidental behavior changes when adding new call sites.

Copilot uses AI. Check for mistakes.
}
CONFIG="$AIRC_WRITE_DIR/config.json"
IDENTITY_DIR="$AIRC_WRITE_DIR/identity"
Expand Down Expand Up @@ -2191,21 +2193,17 @@ cmd_connect() {
| awk -F'\t' -v re="airc room: ${resolved_room_name}\$" -v skip="$_resolved_gist_id" \
'$2 ~ re && $1 != skip { print $1; exit }')

local _preserved_name; _preserved_name=$(get_config_val name "")
rm -f "$CONFIG"
rm -f "$AIRC_WRITE_DIR/room_name"
rm -f "$CONFIG" "$AIRC_WRITE_DIR/room_name"

if [ -n "$_new_picked" ]; then
echo " ✓ Another tab beat us to it — joining their fresh gist ($_new_picked)"
echo ""
_write_reexec_marker
exec env ${_preserved_name:+AIRC_NAME="$_preserved_name"} "$0" connect "$_new_picked"
_reexec_into rejoin "$_new_picked"
fi

echo " Re-execing into host mode for #${resolved_room_name}..."
echo ""
_write_reexec_marker
exec env AIRC_NO_DISCOVERY=1 ${_preserved_name:+AIRC_NAME="$_preserved_name"} "$0" connect --room "$resolved_room_name"
_reexec_into host --room "$resolved_room_name"
fi

# Parse name@user@host[:port]#pubkey
Expand Down Expand Up @@ -2391,30 +2389,19 @@ except Exception:
| awk -F'\t' -v re="airc room: ${resolved_room_name}\$" -v skip="$_resolved_gist_id" \
'$2 ~ re && $1 != skip { print $1; exit }')

# Preserve identity name across re-exec (same reason as resume
# path: derive_name re-runs from cwd and can drift on case-
# aliasing, peers see a "new" peer).
local _preserved_name; _preserved_name=$(get_config_val name "")
# Wipe the CONFIG we just wrote — it points at the dead host
# and would trigger 'resume joiner' on next airc connect.
rm -f "$CONFIG"
rm -f "$AIRC_WRITE_DIR/room_name"
rm -f "$CONFIG" "$AIRC_WRITE_DIR/room_name"

if [ -n "$_new_picked" ]; then
echo " ✓ Another tab beat us to it — joining their fresh gist ($_new_picked)"
echo ""
# Re-exec as joiner pointing at the winner's gist.
_write_reexec_marker
exec env ${_preserved_name:+AIRC_NAME="$_preserved_name"} "$0" connect "$_new_picked"
_reexec_into rejoin "$_new_picked"
fi

echo " Re-execing into host mode for #${resolved_room_name}..."
echo ""
# exec replaces the current bash process. AIRC_NO_DISCOVERY=1
# prevents the new instance from re-finding the just-deleted gist
# (gh's gist-list cache might still show it for a few seconds).
_write_reexec_marker
exec env AIRC_NO_DISCOVERY=1 ${_preserved_name:+AIRC_NAME="$_preserved_name"} "$0" connect --room "$resolved_room_name"
_reexec_into host --room "$resolved_room_name"
fi
# Either not a room flow, or no gh, or no resolved_room_name → original die.
# Surface the captured pair-handshake stderr (continuum-b69f 2026-04-27:
Expand Down Expand Up @@ -2853,9 +2840,7 @@ JSON
"$AIRC_WRITE_DIR/host_gist_id" \
"$AIRC_WRITE_DIR/room_gist_id" \
"$AIRC_WRITE_DIR/room_name"
local _preserved_name; _preserved_name=$(get_config_val name "")
_write_reexec_marker
exec env ${_preserved_name:+AIRC_NAME="$_preserved_name"} "$0" connect "$_winner_id"
_reexec_into rejoin "$_winner_id"
fi
fi

Expand Down Expand Up @@ -5067,14 +5052,8 @@ _daemon_install_schtasks() {
cwd_win=$(printf '%s' "$(pwd -P)" | sed 's|^/\([a-z]\)/|\U\1:\\\\|; s|/|\\\\|g')
airc_bin_unix="$airc_bin"
fi
# Marker path the daemon-launcher polls between iterations to
# distinguish "intentional re-exec into different mode" from "actual
# crash" (#203). airc itself writes this file via _write_reexec_marker
# right before any `exec env ... "$0" connect ...` call. On Windows
# MSYS-bash, exec is emulated as spawn-and-exit (not a true execve),
# so the launcher .bat sees the original bash exit while the new
# airc takes over — the marker tells the .bat to step aside instead
# of racing-respawn the new airc with another instance.
# Marker path the .bat polls to distinguish intentional re-exec
# (written by _reexec_into) from "actual crash" (#203/#204).
local marker_win
if command -v cygpath >/dev/null 2>&1; then
marker_win=$(cygpath -w "$scope/airc.reexec-marker")
Expand Down
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