[llvm-objcopy][NFC] refactor error handling. part 1.

Remove usages of special error reporting functions(error(),
reportError()). This patch is extracted from D87987.
Errors are reported as Expected<>/Error returning values.
This part is for MachO subfolder of llvm-objcopy.

Testing: check-all.

Reviewed By: jhenderson, alexshap

Differential Revision: https://reviews.llvm.org/D88113

Author: avl-llvm

llvm/tools/llvm-objcopy/MachO/MachOObjcopy.cpp

@@ -360,14 +360,11 @@ static Error handleArgs(const CopyConfig &Config, Object &Obj) {
 Error executeObjcopyOnBinary(const CopyConfig &Config,
                              object::MachOObjectFile &In, Buffer &Out) {
   MachOReader Reader(In);
-  std::unique_ptr<Object> O = Reader.create();
+  Expected<std::unique_ptr<Object>> O = Reader.create();
   if (!O)
-    return createFileError(
-        Config.InputFilename,
-        createStringError(object_error::parse_failed,
-                          "unable to deserialize MachO object"));
+    return createFileError(Config.InputFilename, O.takeError());
 
-  if (Error E = handleArgs(Config, *O))
+  if (Error E = handleArgs(Config, **O))
     return createFileError(Config.InputFilename, std::move(E));
 
   // Page size used for alignment of segment sizes in Mach-O executables and
@@ -383,7 +380,7 @@ Error executeObjcopyOnBinary(const CopyConfig &Config,
     PageSize = 4096;
   }
 
-  MachOWriter Writer(*O, In.is64Bit(), In.isLittleEndian(), PageSize, Out);
+  MachOWriter Writer(**O, In.is64Bit(), In.isLittleEndian(), PageSize, Out);
   if (auto E = Writer.finalize())
     return E;
   return Writer.write();

llvm/tools/llvm-objcopy/MachO/MachOReader.cpp

@@ -11,6 +11,7 @@
 #include "Object.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/Object/MachO.h"
+#include "llvm/Support/Errc.h"
 #include <memory>
 
 namespace llvm {
@@ -59,9 +60,8 @@ template <> Section constructSection(MachO::section_64 Sec, uint32_t Index) {
   return S;
 }
 
-// TODO: get rid of reportError and make MachOReader return Expected<> instead.
 template <typename SectionType, typename SegmentType>
-std::vector<std::unique_ptr<Section>>
+Expected<std::vector<std::unique_ptr<Section>>>
 extractSections(const object::MachOObjectFile::LoadCommandInfo &LoadCmd,
                 const object::MachOObjectFile &MachOObj,
                 uint32_t &NextSectionIndex) {
@@ -86,14 +86,15 @@ extractSections(const object::MachOObjectFile::LoadCommandInfo &LoadCmd,
     Expected<object::SectionRef> SecRef =
         MachOObj.getSection(NextSectionIndex++);
     if (!SecRef)
-      reportError(MachOObj.getFileName(), SecRef.takeError());
+      return SecRef.takeError();
 
-    if (Expected<ArrayRef<uint8_t>> E =
-            MachOObj.getSectionContents(SecRef->getRawDataRefImpl()))
-      S.Content =
-          StringRef(reinterpret_cast<const char *>(E->data()), E->size());
-    else
-      reportError(MachOObj.getFileName(), E.takeError());
+    Expected<ArrayRef<uint8_t>> Data =
+        MachOObj.getSectionContents(SecRef->getRawDataRefImpl());
+    if (!Data)
+      return Data.takeError();
+
+    S.Content =
+        StringRef(reinterpret_cast<const char *>(Data->data()), Data->size());
 
     S.Relocations.reserve(S.NReloc);
     for (auto RI = MachOObj.section_rel_begin(SecRef->getRawDataRefImpl()),
@@ -113,7 +114,7 @@ extractSections(const object::MachOObjectFile::LoadCommandInfo &LoadCmd,
   return Sections;
 }
 
-void MachOReader::readLoadCommands(Object &O) const {
+Error MachOReader::readLoadCommands(Object &O) const {
   // For MachO sections indices start from 1.
   uint32_t NextSectionIndex = 1;
   for (auto LoadCmd : MachOObj.load_commands()) {
@@ -123,13 +124,20 @@ void MachOReader::readLoadCommands(Object &O) const {
       O.CodeSignatureCommandIndex = O.LoadCommands.size();
       break;
     case MachO::LC_SEGMENT:
-      LC.Sections = extractSections<MachO::section, MachO::segment_command>(
-          LoadCmd, MachOObj, NextSectionIndex);
+      if (Expected<std::vector<std::unique_ptr<Section>>> Sections =
+              extractSections<MachO::section, MachO::segment_command>(
+                  LoadCmd, MachOObj, NextSectionIndex))
+        LC.Sections = std::move(*Sections);
+      else
+        return Sections.takeError();
       break;
     case MachO::LC_SEGMENT_64:
-      LC.Sections =
-          extractSections<MachO::section_64, MachO::segment_command_64>(
-              LoadCmd, MachOObj, NextSectionIndex);
+      if (Expected<std::vector<std::unique_ptr<Section>>> Sections =
+              extractSections<MachO::section_64, MachO::segment_command_64>(
+                  LoadCmd, MachOObj, NextSectionIndex))
+        LC.Sections = std::move(*Sections);
+      else
+        return Sections.takeError();
       break;
     case MachO::LC_SYMTAB:
       O.SymTabCommandIndex = O.LoadCommands.size();
@@ -177,6 +185,7 @@ void MachOReader::readLoadCommands(Object &O) const {
     }
     O.LoadCommands.push_back(std::move(LC));
   }
+  return Error::success();
 }
 
 template <typename nlist_t>
@@ -308,10 +317,11 @@ void MachOReader::readSwiftVersion(Object &O) const {
       }
 }
 
-std::unique_ptr<Object> MachOReader::create() const {
+Expected<std::unique_ptr<Object>> MachOReader::create() const {
   auto Obj = std::make_unique<Object>();
   readHeader(*Obj);
-  readLoadCommands(*Obj);
+  if (Error E = readLoadCommands(*Obj))
+    return std::move(E);
   readSymbolTable(*Obj);
   setSymbolInRelocationInfo(*Obj);
   readRebaseInfo(*Obj);

llvm/tools/llvm-objcopy/MachO/MachOReader.h

@@ -21,14 +21,14 @@ namespace macho {
 class Reader {
 public:
   virtual ~Reader(){};
-  virtual std::unique_ptr<Object> create() const = 0;
+  virtual Expected<std::unique_ptr<Object>> create() const = 0;
 };
 
 class MachOReader : public Reader {
   const object::MachOObjectFile &MachOObj;
 
   void readHeader(Object &O) const;
-  void readLoadCommands(Object &O) const;
+  Error readLoadCommands(Object &O) const;
   void readSymbolTable(Object &O) const;
   void setSymbolInRelocationInfo(Object &O) const;
   void readRebaseInfo(Object &O) const;
@@ -46,7 +46,7 @@ class MachOReader : public Reader {
 public:
   explicit MachOReader(const object::MachOObjectFile &Obj) : MachOObj(Obj) {}
 
-  std::unique_ptr<Object> create() const override;
+  Expected<std::unique_ptr<Object>> create() const override;
 };
 
 } // end namespace macho