bpo-41100: Support macOS 11 and Apple Silicon (GH-22855)

Co-authored-by:  Lawrence D’Anna <lawrence_danna@apple.com>

* Add support for macOS 11 and Apple Silicon (aka arm64)
   
  As a side effect of this work use the system copy of libffi on macOS, and remove the vendored copy

* Support building on recent versions of macOS while deploying to older versions

  This allows building installers on macOS 11 while still supporting macOS 10.9.

2 files changed, 60 insertions, 13 deletions

diff --git a/Python/bootstrap_hash.c b/Python/bootstrap_hash.c
index 4736930..a212f69 100644
--- a/Python/bootstrap_hash.c
+++ b/Python/bootstrap_hash.c
@@ -25,6 +25,16 @@
 #  include <sanitizer/msan_interface.h>
 #endif
 
+#if defined(__APPLE__) && defined(__has_builtin) 
+#  if __has_builtin(__builtin_available)
+#    define HAVE_GETENTRYPY_GETRANDOM_RUNTIME __builtin_available(macOS 10.12, iOS 10.10, tvOS 10.0, watchOS 3.0, *)
+#  endif
+#endif
+#ifndef HAVE_GETENTRYPY_GETRANDOM_RUNTIME
+#  define HAVE_GETENTRYPY_GETRANDOM_RUNTIME 1
+#endif
+
+
 #ifdef Py_DEBUG
 int _Py_HashSecret_Initialized = 0;
 #else
@@ -208,6 +218,16 @@ py_getrandom(void *buffer, Py_ssize_t size, int blocking, int raise)
      error.
 
    getentropy() is retried if it failed with EINTR: interrupted by a signal. */
+
+#if defined(__APPLE__) && defined(__has_attribute) && __has_attribute(availability)
+static int
+py_getentropy(char *buffer, Py_ssize_t size, int raise) 
+        __attribute__((availability(macos,introduced=10.12)))
+        __attribute__((availability(ios,introduced=10.0)))
+        __attribute__((availability(tvos,introduced=10.0)))
+        __attribute__((availability(watchos,introduced=3.0)));
+#endif
+
 static int
 py_getentropy(char *buffer, Py_ssize_t size, int raise)
 {
@@ -498,19 +518,21 @@ pyurandom(void *buffer, Py_ssize_t size, int blocking, int raise)
 #else
 
 #if defined(PY_GETRANDOM) || defined(PY_GETENTROPY)
+    if (HAVE_GETENTRYPY_GETRANDOM_RUNTIME) {
 #ifdef PY_GETRANDOM
-    res = py_getrandom(buffer, size, blocking, raise);
+        res = py_getrandom(buffer, size, blocking, raise);
 #else
-    res = py_getentropy(buffer, size, raise);
+        res = py_getentropy(buffer, size, raise);
 #endif
-    if (res < 0) {
-        return -1;
-    }
-    if (res == 1) {
-        return 0;
-    }
-    /* getrandom() or getentropy() function is not available: failed with
-       ENOSYS or EPERM. Fall back on reading from /dev/urandom. */
+        if (res < 0) {
+            return -1;
+        }
+        if (res == 1) {
+            return 0;
+        }
+        /* getrandom() or getentropy() function is not available: failed with
+           ENOSYS or EPERM. Fall back on reading from /dev/urandom. */
+        } /* end of availability block */
 #endif
 
     return dev_urandom(buffer, size, raise);
diff --git a/Python/pytime.c b/Python/pytime.c
index b121b43..89d63e0 100644
--- a/Python/pytime.c
+++ b/Python/pytime.c
@@ -5,6 +5,12 @@
 
 #if defined(__APPLE__)
 #include <mach/mach_time.h>   /* mach_absolute_time(), mach_timebase_info() */
+
+#if defined(__APPLE__) && defined(__has_builtin) 
+#  if __has_builtin(__builtin_available)
+#    define HAVE_CLOCK_GETTIME_RUNTIME __builtin_available(macOS 10.12, iOS 10.0, tvOS 10.0, watchOS 3.0, *)
+#  endif
+#endif
 #endif
 
 #define _PyTime_check_mul_overflow(a, b) \
@@ -683,15 +689,22 @@ pygettimeofday(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
 
 #else   /* MS_WINDOWS */
     int err;
-#ifdef HAVE_CLOCK_GETTIME
+#if defined(HAVE_CLOCK_GETTIME)
     struct timespec ts;
-#else
+#endif
+
+#if !defined(HAVE_CLOCK_GETTIME) || defined(__APPLE__)
     struct timeval tv;
 #endif
 
     assert(info == NULL || raise);
 
 #ifdef HAVE_CLOCK_GETTIME
+
+#ifdef HAVE_CLOCK_GETTIME_RUNTIME
+    if (HAVE_CLOCK_GETTIME_RUNTIME) {
+#endif
+
     err = clock_gettime(CLOCK_REALTIME, &ts);
     if (err) {
         if (raise) {
@@ -715,7 +728,14 @@ pygettimeofday(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
             info->resolution = 1e-9;
         }
     }
-#else   /* HAVE_CLOCK_GETTIME */
+
+#ifdef HAVE_CLOCK_GETTIME_RUNTIME
+    } else { 
+#endif
+
+#endif
+
+#if !defined(HAVE_CLOCK_GETTIME) || defined(HAVE_CLOCK_GETTIME_RUNTIME)
 
      /* test gettimeofday() */
     err = gettimeofday(&tv, (struct timezone *)NULL);
@@ -735,6 +755,11 @@ pygettimeofday(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
         info->monotonic = 0;
         info->adjustable = 1;
     }
+
+#if defined(HAVE_CLOCK_GETTIME_RUNTIME) && defined(HAVE_CLOCK_GETTIME)
+    } /* end of availibity block */
+#endif
+
 #endif   /* !HAVE_CLOCK_GETTIME */
 #endif   /* !MS_WINDOWS */
     return 0;