Move watchdog timer disable check to common/utils

We may also want to check this from the plugin.

src/common/utils.cpp

@@ -23,6 +23,15 @@
 namespace bp = boost::process;
 namespace fs = boost::filesystem;
 
+using namespace std::literals::string_literals;
+
+/**
+ * If this environment variable is set to `1`, then we won't enable the watchdog
+ * timer. This is only necessary when running the Wine process under a different
+ * namespace than the host.
+ */
+constexpr char disable_watchdog_timer_env_var[] = "YABRIDGE_NO_WATCHDOG";
+
 fs::path get_temporary_directory() {
     bp::environment env = boost::this_process::environment();
     if (!env["XDG_RUNTIME_DIR"].empty()) {
@@ -57,6 +66,13 @@ std::optional<rlim_t> get_rttime_limit() noexcept {
     }
 }
 
+bool is_watchdog_timer_disabled() {
+    // This is safe because we're not storing the pointer anywhere and the
+    // environment doesn't get modified anywhere
+    // NOLINTNEXTLINE(concurrency-mt-unsafe)
+    return getenv(disable_watchdog_timer_env_var) == "1"s;
+}
+
 bool pid_running(pid_t pid) {
     // With regular individually hosted plugins we can simply check whether the
     // process is still running, however Boost.Process does not allow you to do

src/common/utils.h

@@ -117,6 +117,16 @@ bool set_realtime_priority(bool sched_fifo, int priority = 5) noexcept;
  */
 std::optional<rlim_t> get_rttime_limit() noexcept;
 
+/**
+ * Returns `true` if `YABRIDGE_NO_WATCHDOG` is set to `1`. In that case we will
+ * not check if the Wine plugin host process successfully started, and we'll
+ * also don't check if the native plugin host is still alive. Disabling the
+ * watchdog timers can cause plugins hang during scanning and dangling Wine
+ * processes to be left running, so this should only ever be used when running
+ * the Wine plugin host under a separate namespace.
+ */
+bool is_watchdog_timer_disabled();
+
 /**
  * Check whether a process with the given PID is still active (and not a
  * zombie).