diff --git a/arch/sim/src/cmake/Toolchain.cmake b/arch/sim/src/cmake/Toolchain.cmake
index e326dca663e54..01e11909ccccb 100644
--- a/arch/sim/src/cmake/Toolchain.cmake
+++ b/arch/sim/src/cmake/Toolchain.cmake
@@ -135,6 +135,9 @@ endif()
 if(CONFIG_COVERAGE_ALL)
   if(CONFIG_ARCH_TOOLCHAIN_GCC)
     add_compile_options(-fprofile-arcs -ftest-coverage -fno-inline)
+    if(APPLE)
+      add_link_options(-fprofile-arcs -ftest-coverage)
+    endif()
   elseif(CONFIG_ARCH_TOOLCHAIN_CLANG)
     add_compile_options(-fprofile-instr-generate -fcoverage-mapping)
     add_link_options(-fprofile-instr-generate)
diff --git a/arch/sim/src/sim/CMakeLists.txt b/arch/sim/src/sim/CMakeLists.txt
index 47d1efd8888d9..f5d091a39d496 100644
--- a/arch/sim/src/sim/CMakeLists.txt
+++ b/arch/sim/src/sim/CMakeLists.txt
@@ -29,7 +29,9 @@ set(HOSTSRCS)
 set(HOST_INCLUDE_DIRS)
 set(STDLIBS pthread)
 
-if(CONFIG_COVERAGE_TOOLCHAIN)
+if(CONFIG_COVERAGE_TOOLCHAIN
+   AND CONFIG_ARCH_TOOLCHAIN_GCC
+   AND NOT APPLE)
   list(APPEND STDLIBS gcov)
 endif()
 
diff --git a/arch/sim/src/sim/posix/sim_macho_init.c b/arch/sim/src/sim/posix/sim_macho_init.c
index 28f1c3ad0c4cf..8577abe394189 100644
--- a/arch/sim/src/sim/posix/sim_macho_init.c
+++ b/arch/sim/src/sim/posix/sim_macho_init.c
@@ -27,6 +27,8 @@
 #include <sys/mman.h>
 
 #include <assert.h>
+#include <stdbool.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <unistd.h>
 
@@ -78,11 +80,12 @@ static void save_and_replace_init_funcs(int argc, const char *argv[],
                                         const char *apple[])
 {
   init_func_t *fp;
+  bool found_self = false;
+  unsigned int i;
   unsigned int nfuncs = &mod_init_func_end - &mod_init_func_start;
 
   assert(nfuncs > 0);
-  g_num_saved_init_funcs = nfuncs - 1;
-  if (g_num_saved_init_funcs == 0)
+  if (nfuncs == 1)
     {
       /* This function is the only constructor in the binary.
        * no need to apply the following hack.
@@ -96,23 +99,28 @@ static void save_and_replace_init_funcs(int argc, const char *argv[],
   g_saved_envp = envp;
   g_saved_apple = apple;
 
-  g_saved_init_funcs = malloc(g_num_saved_init_funcs *
-                              sizeof(*g_saved_init_funcs));
+  g_saved_init_funcs = malloc((nfuncs - 1) * sizeof(*g_saved_init_funcs));
   allow_write(&mod_init_func_start, &mod_init_func_end);
-  int i = 0;
+  i = 0;
   for (fp = &mod_init_func_start; fp < &mod_init_func_end; fp++)
     {
       if (*fp == save_and_replace_init_funcs)
         {
-          assert(i == 0);
+          found_self = true;
+          continue;
         }
-      else
+
+      if (found_self)
         {
-          g_saved_init_funcs[i - 1] = *fp;
+          assert(i < nfuncs - 1);
+          g_saved_init_funcs[i] = *fp;
           *fp = noop;
+          i++;
         }
-      i++;
     }
+
+  assert(found_self);
+  g_num_saved_init_funcs = i;
 }
 
 /****************************************************************************
diff --git a/sched/clock/clock_gettime.c b/sched/clock/clock_gettime.c
index 7d5b0566090d8..ab520170e1a7e 100644
--- a/sched/clock/clock_gettime.c
+++ b/sched/clock/clock_gettime.c
@@ -45,6 +45,20 @@
 #  include "clock/clock_timekeeping.h"
 #endif
 
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#if defined(CONFIG_ARCH_SIM) && defined(CONFIG_HOST_MACOS)
+/* Rust code built for the macOS host uses Darwin's libc clock IDs.  When it
+ * is linked into the NuttX simulator, those values are passed to NuttX's
+ * clock_gettime() implementation instead of Darwin's one.
+ */
+
+#  define DARWIN_CLOCK_MONOTONIC 6
+#  define DARWIN_CLOCK_UPTIME_RAW 8
+#endif
+
 /****************************************************************************
  * Private Functions
  ****************************************************************************/
@@ -97,7 +111,12 @@ int nxclock_gettime(clockid_t clock_id, FAR struct timespec *tp)
       return -EINVAL;
     }
 
-  if (clock_id == CLOCK_MONOTONIC)
+  if (clock_id == CLOCK_MONOTONIC
+#if defined(CONFIG_ARCH_SIM) && defined(CONFIG_HOST_MACOS)
+      || clock_id == DARWIN_CLOCK_MONOTONIC
+      || clock_id == DARWIN_CLOCK_UPTIME_RAW
+#endif
+     )
     {
       /* The the time elapsed since the timer was initialized at power on
        * reset, excluding the time that the system is suspended.