AP_HAL_Linux: Poller: allow to fail constructor

libraries/AP_HAL_Linux/Poller.cpp

@@ -17,6 +17,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>
+#include <stdio.h>
 #include <sys/epoll.h>
 #include <sys/types.h>
 #include <sys/uio.h>
@@ -28,6 +29,14 @@ extern const AP_HAL::HAL &hal;
 
 namespace Linux {
 
+Poller::Poller()
+{
+    _epfd = epoll_create1(EPOLL_CLOEXEC);
+    if (_epfd == -1) {
+        fprintf(stderr, "Failed to create epoll: %m\n");
+    }
+}
+
 bool Poller::register_pollable(Pollable *p, uint32_t events)
 {
     /*

libraries/AP_HAL_Linux/Poller.h

@@ -16,7 +16,6 @@
  */
 #pragma once
 
-#include <sys/epoll.h>
 #include <unistd.h>
 
 #include "AP_HAL/utility/RingBuffer.h"
@@ -63,9 +62,23 @@ protected:
 
 class Poller {
 public:
-    Poller() : _epfd(epoll_create1(EPOLL_CLOEXEC)) { }
-    ~Poller() { close(_epfd); }
+    Poller();
 
+    ~Poller() {
+        if (_epfd >= 0) {
+            close(_epfd);
+        }
+    }
+
+    /*
+     * Check if this Poller is not initialized
+     */
+    bool operator!() const { return _epfd == -1; }
+
+    /*
+     * Check if this Poller is succesfully initialized
+     */
+    explicit operator bool() const { return _epfd != -1; }
 
     /*
      * Register @p in this poller so calls to poll() will wait for
@@ -87,7 +100,8 @@ public:
     int poll() const;
 
 private:
-    int _epfd;
+
+    int _epfd = -1;
 };
 
 }

libraries/AP_HAL_Linux/PollerThread.cpp

@@ -92,6 +92,9 @@ TimerPollable *PollerThread::add_timer(TimerPollable::PeriodicCb cb,
                                        TimerPollable::WrapperCb *wrapper,
                                        uint32_t timeout_usec)
 {
+    if (!_poller) {
+        return nullptr;
+    }
     TimerPollable *p = new TimerPollable(cb, wrapper);
     if (!p || !p->setup_timer(timeout_usec) ||
         !_poller.register_pollable(p, POLLIN)) {
@@ -117,6 +120,10 @@ bool PollerThread::adjust_timer(TimerPollable *p, uint32_t timeout_usec)
 
 void PollerThread::_cleanup_timers()
 {
+    if (!_poller) {
+        return;
+    }
+
     for (auto it = _timers.begin(); it != _timers.end(); it++) {
         TimerPollable *p = *it;
         if (p->_removeme) {
@@ -129,6 +136,10 @@ void PollerThread::_cleanup_timers()
 
 void PollerThread::mainloop()
 {
+    if (!_poller) {
+        return;
+    }
+
     while (true) {
         _poller.poll();
         _cleanup_timers();