unikernel/duniverse/dune_/test/blackbox-tests/test-cases/exec-watch/exec-signal.t

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+Here we test what happens if there is a signal for the program to terminate when we are
+running with dune exec. Signals are dispatched from the operating system. It is usually
+impossible for a program to recover after recieving such a signal.
+
+For dune exec -w, we are indifferent to what the process we are running is actually doing
+since it shouldn't affect dune's other functions.
+
+  $ DONE_FLAG=_build/done_flag
+
+  $ cat > dune-project <<EOF
+  > (lang dune 3.18)
+  > EOF
+
+  $ cat > dune <<EOF
+  > (executable
+  >  (name foo)
+  >  (libraries unix))
+  > EOF
+
+  $ cat > touch.ml <<EOF
+  > let touch path =
+  >  let fd = Unix.openfile path [ Unix.O_CREAT ] 0o777 in
+  >  Unix.close fd
+  > ;;
+  > EOF
+
+This first program will signal itself with a KILL signal.:
+  $ cat > foo.ml <<EOF
+  > let () =
+  >   Touch.touch "$DONE_FLAG";
+  >   print_endline "about to be killed";
+  >   let pid = Unix.getpid () in
+  >   Unix.kill pid Sys.sigkill
+  > ;;
+  > EOF
+
+  $ LOG_FILE=_build/log_file
+  $ mkdir _build
+
+When reaching a signal like SEGV dune exec -w will exit.
+  $ dune exec -w ./foo.exe 2> >(tee "$LOG_FILE" >&2) &
+  about to be killed
+  Command got signal KILL.
+  Had 1 error, waiting for filesystem changes...
+  fixed signal
+  Success, waiting for filesystem changes...
+  $ PID=$!
+  $ ./wait-for-file.sh $DONE_FLAG
+
+Waiting for KILL signal...
+  $ tail -f "$LOG_FILE" | while read line; do
+  >   echo "$line" | grep 'KILL' && break
+  > done
+  Command got signal KILL.
+
+We can now start a new build by modifying the original program and removing the segfault.
+This rebuilds successfully as indicated by the above output.
+  $ cat > foo.ml <<EOF
+  > let () =
+  >   Touch.touch "$DONE_FLAG";
+  >   print_endline "fixed signal";
+  > ;;
+  > EOF
+
+  $ ./wait-for-file.sh $DONE_FLAG
+
+  $ kill $PID
+  $ wait $PID
+  [130]