Posix epicsEventWaitWithTimeout() max delay

Limit timeouts on Posix to max-out at 10 years.
Adds a test that will fail when that time-out hits Y2038 on
systems where time_t is still a 32-bit integer.

documentation/RELEASE_NOTES.html

@@ -13,6 +13,16 @@
 
 <!-- Insert new items immediately below here ... -->
 
+<h3>Extend maximum Posix epicsEventWaitWithTimeout() delay</h3>
+
+<p>The Posix implementation of epicsEventWaitWithTimeout() was limiting the
+timeout delay to at most 60 minutes (3600.0 seconds). This has been changed to
+10 years; significantly longer maximum delays cause problems on systems where
+<tt>time_t</tt> is still a signed 32-bit integer so cannot represent absolute
+time-stamps after 2038-01-19. Our assumption is that such 32-bit systems will
+have been retired before the year 2028, but some additional tests have been
+added to the epicsTimeTest program to detect and fail if this assumption is
+violated.</p>
 
 <h3>New test-related make targets</h3>
 

src/libCom/osi/os/Darwin/osdTime.cpp

@@ -67,10 +67,12 @@ convertDoubleToWakeTime(double timeout, struct timespec *wakeTime)
     mach_timespec_t now;
     struct timespec wait;
 
-    clock_get_time(host_clock, &now);
-
     if (timeout < 0.0)
         timeout = 0.0;
+    else if (timeout > 60 * 60 * 24 * 3652.5)
+        timeout = 60 * 60 * 24 * 3652.5;    /* 10 years */
+
+    clock_get_time(host_clock, &now);
 
     wait.tv_sec  = static_cast< time_t >(timeout);
     wait.tv_nsec = static_cast< long >((timeout - (double)wait.tv_sec) * 1e9);

src/libCom/osi/os/posix/osdTime.cpp

@@ -87,30 +87,35 @@ int epicsTime_localtime ( const time_t *clock, // X aCC 361
 extern "C" epicsShareFunc void
     convertDoubleToWakeTime(double timeout,struct timespec *wakeTime)
 {
-    struct timespec wait;
+    struct timespec now, wait;
     int status;
 
     if (timeout < 0.0)
         timeout = 0.0;
+    else if (timeout > 60 * 60 * 24 * 3652.5)
+        timeout = 60 * 60 * 24 * 3652.5;    /* 10 years */
+
 #ifdef CLOCK_REALTIME
-    status = clock_gettime(CLOCK_REALTIME, wakeTime);
+    status = clock_gettime(CLOCK_REALTIME, &now);
 #else
     {
         struct timeval tv;
         struct timezone tz;
         status = gettimeofday(&tv, &tz);
-        wakeTime->tv_sec = tv.tv_sec;
-        wakeTime->tv_nsec = tv.tv_usec * 1000;
+        now.tv_sec = tv.tv_sec;
+        now.tv_nsec = tv.tv_usec * 1000;
     }
 #endif
     if (status) {
         perror("convertDoubleToWakeTime");
         cantProceed("convertDoubleToWakeTime");
     }
+
     wait.tv_sec  = static_cast< time_t >(timeout);
     wait.tv_nsec = static_cast< long >((timeout - (double)wait.tv_sec) * 1e9);
-    wakeTime->tv_sec  += wait.tv_sec;
-    wakeTime->tv_nsec += wait.tv_nsec;
+
+    wakeTime->tv_sec  = now.tv_sec + wait.tv_sec;
+    wakeTime->tv_nsec = now.tv_nsec + wait.tv_nsec;
     if (wakeTime->tv_nsec >= 1000000000L) {
         wakeTime->tv_nsec -= 1000000000L;
         ++wakeTime->tv_sec;

src/libCom/test/epicsTimeTest.cpp

@@ -48,7 +48,7 @@ MAIN(epicsTimeTest)
     const int wasteTime = 100000;
     const int nTimes = 10;
 
-    testPlan(15 + nTimes * 19);
+    testPlan(17 + nTimes * 19);
 
     try {
         const epicsTimeStamp epochTS = {0, 0};
@@ -216,5 +216,35 @@ MAIN(epicsTimeTest)
         testOk1(beginTS + diff == now);
     }
 
+    epicsTime ten_years_hence;
+    try {
+        now = epicsTime::getCurrent();
+        ten_years_hence = now + 60 * 60 * 24 * 3652.5;
+        testPass("epicsTime can represent 10 years hence");
+    }
+    catch ( ... ) {
+        testFail("epicsTime exception for value 10 years hence");
+    }
+
+    try {
+        /* This test exists because in libCom/osi/os/posix/osdTime.cpp
+         * the convertDoubleToWakeTime() routine limits the timeout delay
+         * to 10 years. libCom/timer/timerQueue.cpp returns DBL_MAX for
+         * queues with no timers present, and convertDoubleToWakeTime()
+         * has to return an absolute Posix timestamp. On 2028-01-19 any
+         * systems that still implement time_t as a signed 32-bit integer
+         * will be unable to represent that timestamp, so this will fail.
+         */
+        time_t_wrapper os_time_t = ten_years_hence;
+        epicsTime then = os_time_t; // No fractional seconds
+        double delta = ten_years_hence - then;
+
+        testOk(delta >= 0 && delta < 1.0,
+            "OS time_t can represent 10 years hence");
+    }
+    catch ( ... ) {
+        testFail("OS time_t conversion exception for value 10 years hence");
+    }
+
     return testDone();
 }