[Darwin] Remove obsolete OS version checks

[yln]

Summary

The oldest supported deployment target currently is 10.7 [1]. We can
remove a few outdated checks.

[1] https://github.com/llvm/llvm-project/blob/3db893b3712a5cc98ac0dbc88e08df70069be216/compiler-rt/cmake/config-ix.cmake#L397

[delcypher]

LGTM. Nice clean up!

compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc

 #define wait4 __wait450
 extern const unsigned short *_ctype_tab_;
 extern const short *_toupper_tab_;
 extern const short *_tolower_tab_;
 #endif
 
 // Platform-specific options.
 #if SANITIZER_MAC
-namespace __sanitizer {
-bool PlatformHasDifferentMemcpyAndMemmove();
-}
-#define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE \
-  (__sanitizer::PlatformHasDifferentMemcpyAndMemmove())
+#define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE false
 #elif SANITIZER_WINDOWS64
 #define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE false
 #else
 #define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE true
 #endif  // SANITIZER_MAC
 
 #ifndef COMMON_INTERCEPTOR_INITIALIZE_RANGE
 #define COMMON_INTERCEPTOR_INITIALIZE_RANGE(p, size) {}

compiler-rt/lib/sanitizer_common/sanitizer_mac.h

struct MemoryMappingLayoutData {
   int current_load_cmd_count;
   const char *current_load_cmd_addr;
   bool current_instrumented;
 };
 
 enum MacosVersion {
   MACOS_VERSION_UNINITIALIZED = 0,
   MACOS_VERSION_UNKNOWN,
-  MACOS_VERSION_LEOPARD,
-  MACOS_VERSION_SNOW_LEOPARD,
-  MACOS_VERSION_LION,
+  MACOS_VERSION_LION,  // macOS 10.7; oldest currently supported
   MACOS_VERSION_MOUNTAIN_LION,
   MACOS_VERSION_MAVERICKS,
   MACOS_VERSION_YOSEMITE,
   MACOS_VERSION_EL_CAPITAN,
   MACOS_VERSION_SIERRA,
   MACOS_VERSION_HIGH_SIERRA,
   MACOS_VERSION_HIGH_SIERRA_DOT_RELEASE_4,
   MACOS_VERSION_MOJAVE,

compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

MacosVersion GetMacosVersionInternal() {
   const char *p = version;
   int major = internal_simple_strtoll(p, &p, /*base=*/10);
   if (*p != '.') return MACOS_VERSION_UNKNOWN;
   p += 1;
   int minor = internal_simple_strtoll(p, &p, /*base=*/10);
   if (*p != '.') return MACOS_VERSION_UNKNOWN;
 
   switch (major) {
-    case 9: return MACOS_VERSION_LEOPARD;
-    case 10: return MACOS_VERSION_SNOW_LEOPARD;
     case 11: return MACOS_VERSION_LION;
     case 12: return MACOS_VERSION_MOUNTAIN_LION;
     case 13: return MACOS_VERSION_MAVERICKS;
     case 14: return MACOS_VERSION_YOSEMITE;
     case 15: return MACOS_VERSION_EL_CAPITAN;
     case 16: return MACOS_VERSION_SIERRA;
     case 17:
       // Not a typo, 17.5 Darwin Kernel Version maps to High Sierra 10.13.4.
MacosVersion result =
       static_cast<MacosVersion>(atomic_load(cache, memory_order_acquire));
   if (result == MACOS_VERSION_UNINITIALIZED) {
     result = GetMacosVersionInternal();
     atomic_store(cache, result, memory_order_release);
   }
   return result;
 }
 
-bool PlatformHasDifferentMemcpyAndMemmove() {
-  // On OS X 10.7 memcpy() and memmove() are both resolved
-  // into memmove$VARIANT$sse42.
-  // See also https://github.com/google/sanitizers/issues/34.
-  // TODO(glider): need to check dynamically that memcpy() and memmove() are
-  // actually the same function.
-  return GetMacosVersion() == MACOS_VERSION_SNOW_LEOPARD;
-}
-
 uptr GetRSS() {
   struct task_basic_info info;
   unsigned count = TASK_BASIC_INFO_COUNT;
   kern_return_t result =
       task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)&info, &count);
   if (UNLIKELY(result != KERN_SUCCESS)) {
     Report("Cannot get task info. Error: %d\n", result);
     Die();

compiler-rt/lib/sanitizer_common/sanitizer_malloc_mac.inc

INTERCEPTOR(malloc_zone_t *, malloc_create_zone,
                              vm_size_t start_size, unsigned zone_flags) {
   COMMON_MALLOC_ENTER();
   uptr page_size = GetPageSizeCached();
   uptr allocated_size = RoundUpTo(sizeof(sanitizer_zone), page_size);
   COMMON_MALLOC_MEMALIGN(page_size, allocated_size);
   malloc_zone_t *new_zone = (malloc_zone_t *)p;
   internal_memcpy(new_zone, &sanitizer_zone, sizeof(sanitizer_zone));
   new_zone->zone_name = NULL;  // The name will be changed anyway.
-  if (GetMacosVersion() >= MACOS_VERSION_LION) {
-    // Prevent the client app from overwriting the zone contents.
-    // Library functions that need to modify the zone will set PROT_WRITE on it.
-    // This matches the behavior of malloc_create_zone() on OSX 10.7 and higher.
-    mprotect(new_zone, allocated_size, PROT_READ);
-  }
   // We're explicitly *NOT* registering the zone.
   return new_zone;
 }
 
 INTERCEPTOR(void, malloc_destroy_zone, malloc_zone_t *zone) {
   COMMON_MALLOC_ENTER();
   // We don't need to do anything here.  We're not registering new zones, so we
   // don't to unregister.  Just un-mprotect and free() the zone.
-  if (GetMacosVersion() >= MACOS_VERSION_LION) {
-    uptr page_size = GetPageSizeCached();
-    uptr allocated_size = RoundUpTo(sizeof(sanitizer_zone), page_size);
-    mprotect(zone, allocated_size, PROT_READ | PROT_WRITE);
-  }
   if (zone->zone_name) {
     COMMON_MALLOC_FREE((void *)zone->zone_name);
   }
   COMMON_MALLOC_FREE(zone);
 }
 
 INTERCEPTOR(malloc_zone_t *, malloc_default_zone, void) {
   COMMON_MALLOC_ENTER();