Test whether a system is running 10.7 or later

LionOrLater.cpp

#define MAC_OS_X_VERSION_10_7_HEX 0x00001070

static int sOnLionOrLater = -1;

static bool OnLionOrLater()
{
  if (sOnLionOrLater < 0) {
    SInt32 major = 0, minor = 0;

    CFURLRef url =
      CFURLCreateWithString(kCFAllocatorDefault,
                            CFSTR("file:///System/Library/CoreServices/SystemVersion.plist"),
                            NULL);
    CFReadStreamRef stream =
      CFReadStreamCreateWithFile(kCFAllocatorDefault, url);
    CFReadStreamOpen(stream);
    CFDictionaryRef sysVersionPlist = (CFDictionaryRef)
      CFPropertyListCreateWithStream(kCFAllocatorDefault,
                                     stream, 0, kCFPropertyListImmutable,
                                     NULL, NULL);
    CFReadStreamClose(stream);
    CFRelease(stream);
    CFRelease(url);

    CFStringRef versionString = (CFStringRef)
      CFDictionaryGetValue(sysVersionPlist, CFSTR("ProductVersion"));
    CFArrayRef versions =
      CFStringCreateArrayBySeparatingStrings(kCFAllocatorDefault,
                                             versionString, CFSTR("."));
    CFIndex count = CFArrayGetCount(versions);
    if (count > 0) {
      CFStringRef component = (CFStringRef) CFArrayGetValueAtIndex(versions, 0);
      major = CFStringGetIntValue(component);
      if (count > 1) {
        component = (CFStringRef) CFArrayGetValueAtIndex(versions, 1);
        minor = CFStringGetIntValue(component);
      }
    }
    CFRelease(sysVersionPlist);
    CFRelease(versions);

    if (major < 10) {
      sOnLionOrLater = 0;
    } else {
      int version = 0x1000 + (minor << 4);
      sOnLionOrLater = version >= MAC_OS_X_VERSION_10_7_HEX ? 1 : 0;
    }
  }

  return sOnLionOrLater > 0 ? true : false;
}