Add a configure option to exit on poll errors

If an error is returned from qt_safe_poll inside the event dispatcher
the error is currently printed and ignored.

For most cases this behavior seems to be fine, but when used in critical
systems e.g. automotive or medical, a error might indicate a more severe
problem and the application should be stopped instead.
The system can then decide itself what to do e.g. restarting the
application using a watchdog.

Change-Id: Iaf5abb20bb3941eaeff19d14e41c395c88fa088d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/configure.cmake

@@ -961,6 +961,13 @@ qt_feature("cborstreamwriter" PUBLIC
     LABEL "CBOR stream writing"
     PURPOSE "Provides support for writing the CBOR binary format."
 )
+qt_feature("poll-exit-on-error" PUBLIC
+    LABEL "Poll exit on error"
+    AUTODETECT OFF
+    CONDITION UNIX
+    PURPOSE "Exit on error instead of just printing the error code and continue."
+)
+qt_feature_definition("poll-exit-on-error" "QT_POLL_EXIT_ON_ERROR")
 qt_configure_add_summary_section(NAME "Qt Core")
 qt_configure_add_summary_entry(ARGS "backtrace")
 qt_configure_add_summary_entry(ARGS "doubleconversion")
@@ -970,6 +977,7 @@ qt_configure_add_summary_entry(ARGS "icu")
 qt_configure_add_summary_entry(ARGS "system-libb2")
 qt_configure_add_summary_entry(ARGS "mimetype-database")
 qt_configure_add_summary_entry(ARGS "cpp-winrt")
+qt_configure_add_summary_entry(ARGS "poll-exit-on-error")
 qt_configure_add_summary_entry(
     TYPE "firstAvailableFeature"
     ARGS "etw lttng"

src/corelib/kernel/qeventdispatcher_unix.cpp

@@ -466,7 +466,11 @@ bool QEventDispatcherUNIX::processEvents(QEventLoop::ProcessEventsFlags flags)
 
     switch (qt_safe_poll(d->pollfds.data(), d->pollfds.size(), tm)) {
     case -1:
+#ifdef QT_POLL_EXIT_ON_ERROR
+        qFatal("qt_safe_poll errno: %i error: %ls", errno, qUtf16Printable(qt_error_string()));
+#else
         perror("qt_safe_poll");
+#endif
         break;
     case 0:
         break;