Support clock_gettime() on OSX El Capitan and earlier

Compat.c

@@ -11,12 +11,18 @@ in the source distribution for its full text.
 
 #include <errno.h>
 #include <fcntl.h> // IWYU pragma: keep
+#include <time.h>
 #include <unistd.h>
 #include <sys/stat.h>
 #include <sys/types.h> // IWYU pragma: keep
 
 #include "XUtils.h" // IWYU pragma: keep
 
+#ifdef HAVE_HOST_GET_CLOCK_SERVICE
+#include <mach/clock.h>
+#include <mach/mach.h>
+#endif
+
 
 int Compat_faccessat(int dirfd,
                      const char* pathname,
@@ -117,3 +123,31 @@ ssize_t Compat_readlinkat(int dirfd,
 
 #endif
 }
+
+int Compat_clock_monotonic_gettime(struct timespec *tp) {
+
+#if defined(HAVE_CLOCK_GETTIME)
+
+   return clock_gettime(CLOCK_MONOTONIC, tp);
+
+#elif defined(HAVE_HOST_GET_CLOCK_SERVICE)
+
+   clock_serv_t cclock;
+   mach_timespec_t mts;
+
+   host_get_clock_service(mach_host_self(), SYSTEM_CLOCK, &cclock);
+   clock_get_time(cclock, &mts);
+   mach_port_deallocate(mach_task_self(), cclock);
+
+   tp->tv_sec = mts.tv_sec;
+   tp->tv_nsec = mts.tv_nsec;
+
+   return 0;
+
+#else
+
+#error No Compat_clock_monotonic_gettime() implementation!
+
+#endif
+
+}

Compat.h

@@ -56,4 +56,6 @@ ssize_t Compat_readlinkat(int dirfd,
                           char* buf,
                           size_t bufsize);
 
+int Compat_clock_monotonic_gettime(struct timespec *tp);
+
 #endif /* HEADER_Compat */

ProcessList.c

@@ -10,8 +10,8 @@ in the source distribution for its full text.
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
-#include <time.h>
 
+#include "Compat.h"
 #include "CRT.h"
 #include "Hashtable.h"
 #include "Macros.h"
@@ -538,8 +538,8 @@ void ProcessList_scan(ProcessList* this, bool pauseProcessUpdate) {
    if (!firstScanDone) {
       this->scanTs = 0;
       firstScanDone = true;
-   } else if (clock_gettime(CLOCK_MONOTONIC, &now) == 0) {
-      this->scanTs = now.tv_sec;
+   } else if (Compat_clock_monotonic_gettime(&now) == 0) {
+      this->scanTs = now.tv_sec + now.tv_nsec / 1000000000;
    }
 
    ProcessList_goThroughEntries(this, false);

configure.ac

@@ -93,8 +93,10 @@ AC_TYPE_UINT64_T
 AC_FUNC_CLOSEDIR_VOID
 AC_FUNC_STAT
 AC_CHECK_FUNCS([\
+   clock_gettime\
    faccessat\
    fstatat\
+   host_get_clock_service\
    openat\
    readlinkat\
 ])