Add MachOObjectFile::getUuid()

[glider]

Summary

This CL introduces MachOObjectFile::getUuid(). This function returns an ArrayRef to the object file's UUID, or an empty ArrayRef if the object file doesn't contain an LC_UUID load command.
The new function is gonna be used by llvm-symbolizer.

[kledzik]

The MachOObjectFile constructor is already walking the load commands. If there is a LC_UUID, you can have the constructor save it off in an ivar.

The name findAndGetUuidCommand() is different than the other methods. Can it just be getUUID() and have it return the 16-bytes? Perhaps an ArrayRef<uint8_t> that has zero length if there is no UUID? Seems like that would be more convenient for the client.

-Nick

[glider]

Addressed Nick's comments.

[kledzik]

LGTM

[glider]

r219866, thanks!

include/llvm/Object/MachO.h

public:
   MachO::symtab_command getSymtabLoadCommand() const;
   MachO::dysymtab_command getDysymtabLoadCommand() const;
   MachO::linkedit_data_command getDataInCodeLoadCommand() const;
   ArrayRef<uint8_t> getDyldInfoRebaseOpcodes() const;
   ArrayRef<uint8_t> getDyldInfoBindOpcodes() const;
   ArrayRef<uint8_t> getDyldInfoWeakBindOpcodes() const;
   ArrayRef<uint8_t> getDyldInfoLazyBindOpcodes() const;
   ArrayRef<uint8_t> getDyldInfoExportsTrie() const;
+  ArrayRef<uint8_t> getUuid() const;
 
   StringRef getStringTableData() const;
   bool is64Bit() const;
   void ReadULEB128s(uint64_t Index, SmallVectorImpl<uint64_t> &Out) const;
 
   static StringRef guessLibraryShortName(StringRef Name, bool &isFramework,
                                          StringRef &Suffix);
 
private:
   typedef SmallVector<const char*, 1> LibraryList;
   LibraryList Libraries;
   typedef SmallVector<StringRef, 1> LibraryShortName;
   mutable LibraryShortName LibrariesShortNames;
   const char *SymtabLoadCmd;
   const char *DysymtabLoadCmd;
   const char *DataInCodeLoadCmd;
   const char *DyldInfoLoadCmd;
+  const char *UuidLoadCmd;
   bool HasPageZeroSegment;
 };
 
 /// DiceRef
 inline DiceRef::DiceRef(DataRefImpl DiceP, const ObjectFile *Owner)
   : DicePimpl(DiceP) , OwningObject(Owner) {}
 
 inline bool DiceRef::operator==(const DiceRef &Other) const {

lib/Object/MachOObjectFile.cpp

static uint32_t getSectionFlags(const MachOObjectFile *O,
   return Sect.flags;
 }
 
 MachOObjectFile::MachOObjectFile(MemoryBufferRef Object, bool IsLittleEndian,
                                  bool Is64bits, std::error_code &EC)
     : ObjectFile(getMachOType(IsLittleEndian, Is64bits), Object),
       SymtabLoadCmd(nullptr), DysymtabLoadCmd(nullptr),
       DataInCodeLoadCmd(nullptr), DyldInfoLoadCmd(nullptr),
-      HasPageZeroSegment(false) {
+      UuidLoadCmd(nullptr), HasPageZeroSegment(false) {
   uint32_t LoadCommandCount = this->getHeader().ncmds;
   MachO::LoadCommandType SegmentLoadType = is64Bit() ?
     MachO::LC_SEGMENT_64 : MachO::LC_SEGMENT;
 
   MachOObjectFile::LoadCommandInfo Load = getFirstLoadCommandInfo();
   for (unsigned I = 0; ; ++I) {
     if (Load.C.cmd == MachO::LC_SYMTAB) {
       assert(!SymtabLoadCmd && "Multiple symbol tables");
       SymtabLoadCmd = Load.Ptr;
     } else if (Load.C.cmd == MachO::LC_DYSYMTAB) {
       assert(!DysymtabLoadCmd && "Multiple dynamic symbol tables");
       DysymtabLoadCmd = Load.Ptr;
     } else if (Load.C.cmd == MachO::LC_DATA_IN_CODE) {
       assert(!DataInCodeLoadCmd && "Multiple data in code tables");
       DataInCodeLoadCmd = Load.Ptr;
     } else if (Load.C.cmd == MachO::LC_DYLD_INFO || 
                Load.C.cmd == MachO::LC_DYLD_INFO_ONLY) {
       assert(!DyldInfoLoadCmd && "Multiple dyldinfo load commands");
       DyldInfoLoadCmd = Load.Ptr;
+    } else if (Load.C.cmd == MachO::LC_UUID) {
+      assert(!UuidLoadCmd && "Multiple UUID load commands");
+      UuidLoadCmd = Load.Ptr;
     } else if (Load.C.cmd == SegmentLoadType) {
       uint32_t NumSections = getSegmentLoadCommandNumSections(this, Load);
       for (unsigned J = 0; J < NumSections; ++J) {
         const char *Sec = getSectionPtr(this, Load, J);
         Sections.push_back(Sec);
       }
       if (isPageZeroSegment(this, Load))
         HasPageZeroSegment = true;
ArrayRef<uint8_t> MachOObjectFile::getDyldInfoExportsTrie() const {
 
   MachO::dyld_info_command DyldInfo 
                    = getStruct<MachO::dyld_info_command>(this, DyldInfoLoadCmd);
   const uint8_t *Ptr = reinterpret_cast<const uint8_t*>(
                                              getPtr(this, DyldInfo.export_off));
   return ArrayRef<uint8_t>(Ptr, DyldInfo.export_size);
 }
 
+ArrayRef<uint8_t> MachOObjectFile::getUuid() const {
+  if (!UuidLoadCmd)
+    return ArrayRef<uint8_t>();
+  MachO::uuid_command Uuid = getStruct<MachO::uuid_command>(this, UuidLoadCmd);
+  return ArrayRef<uint8_t>(Uuid.uuid, 16);
+}
 
 StringRef MachOObjectFile::getStringTableData() const {
   MachO::symtab_command S = getSymtabLoadCommand();
   return getData().substr(S.stroff, S.strsize);
 }
 
 bool MachOObjectFile::is64Bit() const {
   return getType() == getMachOType(false, true) ||