When I was compiling with MacOSX.SDK, these error occurred /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/hfs/hfs_format.h:796:20: error: unknown type name 'uuid_string_t'; did you mean 'io_string_t'? char reserved[JIB_RESERVED_SIZE]; ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/hfs/hfs_format.h:787:61: note: expanded from macro 'JIB_RESERVED_SIZE' #define JIB_RESERVED_SIZE ((32*sizeof(u_int32_t)) - sizeof(uuid_string_t) - 48) ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/device/device_types.h:89:33: note: 'io_string_t' declared here typedef char io_string_t[512]; I searched on the Internet and found the similar problem, it seems that there is something wrong with uuid.h. Actually, I do have this head file in my project directory. Anybody encountered with the same problem ? How to solve this problem?

My macos update automatically and the new macos SDK are not fit for my program, so how to use a lower version macos SDK? And I have another problem, once I installed Xcode, the SDK will be set path to Xcode path, also I have a command line path which is /Library/Developer/CommandlineTools. In this path, there is also a SDKs directory which contains some different versions of macos SDK? How to set a default SDK path?