Test for 5740 and readonly.

regress/control-client-start-fail.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+
+# The server cannot create its socket, so it sets the control client to exit
+# before the client completes identification. The exit check must not use the
+# control state before MSG_IDENTIFY_DONE creates it. The client must get the
+# reason for the failure in %exit.
+
+PATH=/bin:/usr/bin
+TERM=screen
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+
+DIR=$(mktemp -d)
+SOCK=$DIR/missing/sock
+
+OUT=$($TEST_TMUX -f/dev/null -S$SOCK -C new-session </dev/null 2>&1)
+rm -rf $DIR
+[ "$OUT" = "%exit error creating $SOCK (No such file or directory)" ] || exit 1
+
+exit 0