Follow POSIX exit codes for processes killed by signals

fhunleth · Aug 22, 2019 · dd043d0 · dd043d0
1 parent 22275a2
commit dd043d0
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Showing 5 changed files with 42 additions and 6 deletions.
diff --git a/src/muontrap.c b/src/muontrap.c
@@ -497,9 +497,22 @@ static int child_wait_loop(pid_t child_pid, int *still_running)
                 int status;
                 pid_t dying_pid = wait(&status);
                 if (dying_pid == child_pid) {
-                    int exit_status = WIFEXITED(status) ? WEXITSTATUS(status) : EXIT_FAILURE;
-                    INFO("main child exited. status=%d, our exit code: %d", status, exit_status);
+                    // Let the caller know that the child isn't running and has been cleaned up
                     *still_running = 0;
+
+                    int exit_status;
+                    if (WIFSIGNALED(status)) {
+                        // Crash on signal, return the signal in the exit status. See POSIX:
+                        // http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_08_02
+                        exit_status = 128 + WTERMSIG(status);
+                        INFO("child terminated via signal %d. our exit status: %d", status, exit_status);
+                    } else if (WIFEXITED(status)) {
+                        exit_status = WEXITSTATUS(status);
+                        INFO("child exited with exit status: %d", exit_status);
+                    } else {
+                        INFO("child terminated with unexpected status: %d", status);
+                        exit_status = EXIT_FAILURE;
+                    }
                     return exit_status;
                 } else {
                     INFO("something else caused sigchild: pid=%d, status=%d. our child=%d", dying_pid, status, child_pid);

diff --git a/test/daemon_test.exs b/test/daemon_test.exs
@@ -4,10 +4,6 @@ defmodule DaemonTest do
 
   alias MuonTrap.Daemon
 
-  defp test_path(cmd) do
-    Path.join([File.cwd!(), "test", cmd])
-  end
-
   defp daemon_spec(cmd, args) do
     Supervisor.child_spec({Daemon, [cmd, args]}, id: :test_daemon)
   end

diff --git a/test/kill_self_with_signal.c b/test/kill_self_with_signal.c
@@ -0,0 +1,17 @@
+#include <err.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int main(int argc, char **argv)
+{
+    // This test kills itself with a SIGTERM to see if
+    // muontrap reports the expected exit code.
+    if (kill(getpid(), SIGTERM) < 0)
+        err(EXIT_FAILURE, "kill");
+
+    // Give the OS up to a second to deliver the signal.
+    sleep(1);
+
+    errx(EXIT_FAILURE, "expected a signal");
+}
diff --git a/test/muontrap_test.exs b/test/muontrap_test.exs
@@ -116,6 +116,11 @@ defmodule MuonTrapTest do
     File.rm_rf!(@tmp_path)
   end
 
+  test "signals return an exit code of 128 + signal" do
+    # SIGTERM == 15
+    assert {"", 128 + 15} == MuonTrap.cmd(test_path("kill_self_with_signal.test"), [])
+  end
+
   test "README.md version is up to date" do
     app = :muontrap
     app_version = Application.spec(app, :vsn) |> to_string()

diff --git a/test/support/test_case.ex b/test/support/test_case.ex
@@ -10,6 +10,11 @@ defmodule MuonTrapTest.Case do
 
   @timeout_before_close_check 20
 
+  @spec test_path(Path.t()) :: Path.t()
+  def test_path(cmd) do
+    Path.join([File.cwd!(), "test", cmd])
+  end
+
   @spec cpu_cgroup_exists(String.t()) :: boolean
   def cpu_cgroup_exists(path) do
     {rc, 0} = System.cmd("cgget", ["-g", "cpu", path], stderr_to_stdout: true)