From 3eab3290426a8847910cc1e7ba76a161ae286220 Mon Sep 17 00:00:00 2001
From: Bryan Christianson <bryan@whatroute.net>
Date: Fri, 13 Mar 2020 08:33:00 +1300
Subject: [PATCH] sys_macosx: don't require clock_gettime()

Earlier versions of macOS do not provide clock_gettime(). This patch
checks for clock_gettime() at run-time and falls back to gettimeofday()
if the symbol is not present.
---
 sys_macosx.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/sys_macosx.c b/sys_macosx.c
index 807d62e..701c078 100644
--- a/sys_macosx.c
+++ b/sys_macosx.c
@@ -451,6 +451,39 @@ legacy_MacOSX_Finalise(void)
 
 /* ================================================== */
 
+#if HAVE_CLOCK_GETTIME
+int
+clock_gettime(clockid_t clock_id, struct timespec *ts)
+{
+  /* Check that the system clock_gettime symbol is actually present before
+     attempting to call it. The symbol is available in macOS 10.12
+     and later. */
+
+  static int init = 0;
+  static int (*sys_clock_gettime)(clockid_t, struct timespec *) = NULL;
+  int ret = 0;
+
+  if (!init) {
+    sys_clock_gettime = dlsym(RTLD_NEXT, "clock_gettime");
+    init = 1;
+  }
+
+  if (sys_clock_gettime != NULL) {
+    ret = sys_clock_gettime(clock_id, ts);
+  } else {
+    struct timeval tv;
+
+    if (gettimeofday(&tv, NULL) < 0)
+      LOG_FATAL("gettimeofday() failed : %s", strerror(errno));
+
+    UTI_TimevalToTimespec(&tv, ts);
+  }
+  return ret;
+}
+#endif
+
+/* ================================================== */
+
 void
 SYS_MacOSX_Initialise(void)
 {