Make the Error class constructor protected

This is forcing to use Error::success(), which is in a wide majority
of cases a lot more readable.

Differential Revision: https://reviews.llvm.org/D26481

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286561 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ExecutionEngine/Orc/OrcRemoteTargetClient.h

@@ -589,7 +589,7 @@ public:
   /// Channel is the ChannelT instance to communicate on. It is assumed that
   /// the channel is ready to be read from and written to.
   static Expected<OrcRemoteTargetClient> Create(ChannelT &Channel) {
-    Error Err;
+    Error Err = Error::success();
     OrcRemoteTargetClient H(Channel, Err);
     if (Err)
       return std::move(Err);
@@ -808,7 +808,7 @@ private:
   static Error doNothing() { return Error::success(); }
 
   ChannelT &Channel;
-  Error ExistingError;
+  Error ExistingError = Error::success();
   std::string RemoteTargetTriple;
   uint32_t RemotePointerSize = 0;
   uint32_t RemotePageSize = 0;

include/llvm/Support/Error.h

@@ -149,14 +149,14 @@ class LLVM_NODISCARD Error {
   // error.
   template <typename T> friend class Expected;
 
-public:
+protected:
   /// Create a success value. Prefer using 'Error::success()' for readability
-  /// where possible.
   Error() : Payload(nullptr) {
     setPtr(nullptr);
     setChecked(false);
   }
 
+public:
   /// Create a success value. This is equivalent to calling the default
   /// constructor, but should be preferred for readability where possible.
   static Error success() { return Error(); }

lib/LTO/LTO.cpp

@@ -437,7 +437,7 @@ Error LTO::addThinLTO(std::unique_ptr<InputFile> Input,
   assert(ResI == Res.end());
 
   ThinLTO.ModuleMap[MBRef.getBufferIdentifier()] = MBRef;
-  return Error();
+  return Error::success();
 }
 
 unsigned LTO::getMaxTasks() const {
@@ -489,7 +489,7 @@ Error LTO::runRegularLTO(AddStreamFn AddStream) {
 
   if (Conf.PreOptModuleHook &&
       !Conf.PreOptModuleHook(0, *RegularLTO.CombinedModule))
-    return Error();
+    return Error::success();
 
   if (!Conf.CodeGenOnly) {
     for (const auto &R : GlobalResolutions) {
@@ -512,7 +512,7 @@ Error LTO::runRegularLTO(AddStreamFn AddStream) {
 
     if (Conf.PostInternalizeModuleHook &&
         !Conf.PostInternalizeModuleHook(0, *RegularLTO.CombinedModule))
-      return Error();
+      return Error::success();
   }
   return backend(Conf, AddStream, RegularLTO.ParallelCodeGenParallelismLevel,
                  std::move(RegularLTO.CombinedModule));
@@ -593,7 +593,7 @@ public:
     if (AddStreamFn CacheAddStream = Cache(Task, Key))
       return RunThinBackend(CacheAddStream);
 
-    return Error();
+    return Error::success();
   }
 
   Error start(
@@ -628,7 +628,7 @@ public:
         MBRef, std::ref(CombinedIndex), std::ref(ImportList),
         std::ref(ExportList), std::ref(ResolvedODR), std::ref(DefinedGlobals),
         std::ref(ModuleMap));
-    return Error();
+    return Error::success();
   }
 
   Error wait() override {
@@ -636,7 +636,7 @@ public:
     if (Err)
       return std::move(*Err);
     else
-      return Error();
+      return Error::success();
   }
 };
 
@@ -722,10 +722,10 @@ public:
     if (ShouldEmitImportsFiles)
       return errorCodeToError(
           EmitImportsFiles(ModulePath, NewModulePath + ".imports", ImportList));
-    return Error();
+    return Error::success();
   }
 
-  Error wait() override { return Error(); }
+  Error wait() override { return Error::success(); }
 };
 
 ThinBackend lto::createWriteIndexesThinBackend(std::string OldPrefix,
@@ -744,10 +744,10 @@ ThinBackend lto::createWriteIndexesThinBackend(std::string OldPrefix,
 Error LTO::runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache,
                       bool HasRegularLTO) {
   if (ThinLTO.ModuleMap.empty())
-    return Error();
+    return Error::success();
 
   if (Conf.CombinedIndexHook && !Conf.CombinedIndexHook(ThinLTO.CombinedIndex))
-    return Error();
+    return Error::success();
 
   // Collect for each module the list of function it defines (GUID ->
   // Summary).

lib/LTO/LTOBackend.cpp

@@ -105,7 +105,7 @@ Error Config::addSaveTemps(std::string OutputFileName,
     return true;
   };
 
-  return Error();
+  return Error::success();
 }
 
 namespace {
@@ -302,7 +302,7 @@ Error lto::backend(Config &C, AddStreamFn AddStream,
 
   if (!C.CodeGenOnly)
     if (!opt(C, TM.get(), 0, *Mod, /*IsThinLto=*/false))
-      return Error();
+      return Error::success();
 
   if (ParallelCodeGenParallelismLevel == 1) {
     codegen(C, TM.get(), AddStream, 0, *Mod);
@@ -310,7 +310,7 @@ Error lto::backend(Config &C, AddStreamFn AddStream,
     splitCodeGen(C, TM.get(), AddStream, ParallelCodeGenParallelismLevel,
                  std::move(Mod));
   }
-  return Error();
+  return Error::success();
 }
 
 Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
@@ -329,25 +329,25 @@ Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
 
   if (Conf.CodeGenOnly) {
     codegen(Conf, TM.get(), AddStream, Task, Mod);
-    return Error();
+    return Error::success();
   }
 
   if (Conf.PreOptModuleHook && !Conf.PreOptModuleHook(Task, Mod))
-    return Error();
+    return Error::success();
 
   renameModuleForThinLTO(Mod, CombinedIndex);
 
   thinLTOResolveWeakForLinkerModule(Mod, DefinedGlobals);
 
   if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod))
-    return Error();
+    return Error::success();
 
   if (!DefinedGlobals.empty())
     thinLTOInternalizeModule(Mod, DefinedGlobals);
 
   if (Conf.PostInternalizeModuleHook &&
       !Conf.PostInternalizeModuleHook(Task, Mod))
-    return Error();
+    return Error::success();
 
   auto ModuleLoader = [&](StringRef Identifier) {
     assert(Mod.getContext().isODRUniquingDebugTypes() &&
@@ -363,11 +363,11 @@ Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
     return Err;
 
   if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod))
-    return Error();
+    return Error::success();
 
   if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLto=*/true))
-    return Error();
+    return Error::success();
 
   codegen(Conf, TM.get(), AddStream, Task, Mod);
-  return Error();
+  return Error::success();
 }

lib/Object/Archive.cpp

@@ -458,7 +458,7 @@ Expected<Archive::Child> Archive::Child::getNext() const {
       return malformedError(Msg + NameOrErr.get());
   }
 
-  Error Err;
+  Error Err = Error::success();
   Child Ret(Parent, NextLoc, &Err);
   if (Err)
     return std::move(Err);
@@ -508,7 +508,7 @@ Archive::Child::getAsBinary(LLVMContext *Context) const {
 }
 
 Expected<std::unique_ptr<Archive>> Archive::create(MemoryBufferRef Source) {
-  Error Err;
+  Error Err = Error::success();
   std::unique_ptr<Archive> Ret(new Archive(Source, Err));
   if (Err)
     return std::move(Err);
@@ -830,7 +830,7 @@ Expected<Archive::Child> Archive::Symbol::getMember() const {
   }
 
   const char *Loc = Parent->getData().begin() + Offset;
-  Error Err;
+  Error Err = Error::success();
   Child C(Parent, Loc, &Err);
   if (Err)
     return std::move(Err);

lib/Object/Error.cpp

@@ -79,18 +79,17 @@ const std::error_category &object::object_category() {
 
 llvm::Error llvm::object::isNotObjectErrorInvalidFileType(llvm::Error Err) {
   if (auto Err2 =
-       handleErrors(std::move(Err),
-         [](std::unique_ptr<ECError> M) {
-           // Try to handle 'M'. If successful, return a success value from
-           // the handler.
-           if (M->convertToErrorCode() == object_error::invalid_file_type)
-             return Error::success();
+          handleErrors(std::move(Err), [](std::unique_ptr<ECError> M) -> Error {
+            // Try to handle 'M'. If successful, return a success value from
+            // the handler.
+            if (M->convertToErrorCode() == object_error::invalid_file_type)
+              return Error::success();
 
-           // We failed to handle 'M' - return it from the handler.
-           // This value will be passed back from catchErrors and
-           // wind up in Err2, where it will be returned from this function.
-           return Error(std::move(M));
-         }))
+            // We failed to handle 'M' - return it from the handler.
+            // This value will be passed back from catchErrors and
+            // wind up in Err2, where it will be returned from this function.
+            return Error(std::move(M));
+          }))
     return Err2;
   return Err;
 }

lib/Object/MachOObjectFile.cpp

@@ -1073,7 +1073,7 @@ Expected<std::unique_ptr<MachOObjectFile>>
 MachOObjectFile::create(MemoryBufferRef Object, bool IsLittleEndian,
                         bool Is64Bits, uint32_t UniversalCputype,
                         uint32_t UniversalIndex) {
-  Error Err;
+  Error Err = Error::success();
   std::unique_ptr<MachOObjectFile> Obj(
       new MachOObjectFile(std::move(Object), IsLittleEndian,
                           Is64Bits, Err, UniversalCputype,

lib/Object/MachOUniversal.cpp

@@ -107,7 +107,7 @@ void MachOUniversalBinary::anchor() { }
 
 Expected<std::unique_ptr<MachOUniversalBinary>>
 MachOUniversalBinary::create(MemoryBufferRef Source) {
-  Error Err;
+  Error Err = Error::success();
   std::unique_ptr<MachOUniversalBinary> Ret(
       new MachOUniversalBinary(Source, Err));
   if (Err)

lib/ProfileData/Coverage/CoverageMappingReader.cpp

@@ -648,7 +648,7 @@ BinaryCoverageReader::create(std::unique_ptr<MemoryBuffer> &ObjectBuffer,
   StringRef Coverage;
   uint8_t BytesInAddress;
   support::endianness Endian;
-  Error E;
+  Error E = Error::success();
   consumeError(std::move(E));
   if (ObjectBuffer->getBuffer().startswith(TestingFormatMagic))
     // This is a special format used for testing.

tools/dsymutil/BinaryHolder.cpp

@@ -100,7 +100,7 @@ ErrorOr<std::vector<MemoryBufferRef>> BinaryHolder::GetArchiveMemberBuffers(
   Buffers.reserve(CurrentArchives.size());
 
   for (const auto &CurrentArchive : CurrentArchives) {
-    Error Err;
+    Error Err = Error::success();
     for (auto Child : CurrentArchive->children(Err)) {
       if (auto NameOrErr = Child.getName()) {
         if (*NameOrErr == Filename) {

tools/llvm-ar/llvm-ar.cpp

@@ -423,7 +423,7 @@ static void performReadOperation(ArchiveOperation Operation,
 
   bool Filter = !Members.empty();
   {
-    Error Err;
+    Error Err = Error::success();
     for (auto &C : OldArchive->children(Err)) {
       Expected<StringRef> NameOrErr = C.getName();
       failIfError(NameOrErr.takeError());
@@ -551,7 +551,7 @@ computeNewArchiveMembers(ArchiveOperation Operation,
   int InsertPos = -1;
   StringRef PosName = sys::path::filename(RelPos);
   if (OldArchive) {
-    Error Err;
+    Error Err = Error::success();
     for (auto &Child : OldArchive->children(Err)) {
       int Pos = Ret.size();
       Expected<StringRef> NameOrErr = Child.getName();
@@ -723,7 +723,7 @@ static int performOperation(ArchiveOperation Operation,
     fail("error opening '" + ArchiveName + "': " + EC.message() + "!");
 
   if (!EC) {
-    Error Err;
+    Error Err = Error::success();
     object::Archive Archive(Buf.get()->getMemBufferRef(), Err);
     EC = errorToErrorCode(std::move(Err));
     failIfError(EC,
@@ -785,7 +785,7 @@ static void runMRIScript() {
       Archives.push_back(std::move(*LibOrErr));
       object::Archive &Lib = *Archives.back();
       {
-        Error Err;
+        Error Err = Error::success();
         for (auto &Member : Lib.children(Err))
           addMember(NewMembers, Member);
         failIfError(std::move(Err));

tools/llvm-cxxdump/llvm-cxxdump.cpp

@@ -490,7 +490,7 @@ static void dumpCXXData(const ObjectFile *Obj) {
 }
 
 static void dumpArchive(const Archive *Arc) {
-  Error Err;
+  Error Err = Error::success();
   for (auto &ArcC : Arc->children(Err)) {
     Expected<std::unique_ptr<Binary>> ChildOrErr = ArcC.getAsBinary();
     if (!ChildOrErr) {

tools/llvm-dwp/llvm-dwp.cpp

@@ -364,7 +364,7 @@ static Error handleCompressedSection(
     std::deque<SmallString<32>> &UncompressedSections, StringRef &Name,
     StringRef &Contents) {
   if (!Name.startswith("zdebug_"))
-    return Error();
+    return Error::success();
   UncompressedSections.emplace_back();
   uint64_t OriginalSize;
   if (!zlib::isAvailable())
@@ -377,7 +377,7 @@ static Error handleCompressedSection(
             .str());
   Name = Name.substr(1);
   Contents = UncompressedSections.back();
-  return Error();
+  return Error::success();
 }
 
 static Error handleSection(
@@ -392,10 +392,10 @@ static Error handleSection(
     StringRef &AbbrevSection, StringRef &CurCUIndexSection,
     StringRef &CurTUIndexSection) {
   if (Section.isBSS())
-    return Error();
+    return Error::success();
 
   if (Section.isVirtual())
-    return Error();
+    return Error::success();
 
   StringRef Name;
   if (std::error_code Err = Section.getName(Name))
@@ -412,7 +412,7 @@ static Error handleSection(
 
   auto SectionPair = KnownSections.find(Name);
   if (SectionPair == KnownSections.end())
-    return Error();
+    return Error::success();
 
   if (DWARFSectionKind Kind = SectionPair->second.second) {
     auto Index = Kind - DW_SECT_INFO;
@@ -449,7 +449,7 @@ static Error handleSection(
     Out.SwitchSection(OutSection);
     Out.EmitBytes(Contents);
   }
-  return Error();
+  return Error::success();
 }
 
 static Error
@@ -600,7 +600,7 @@ static Error write(MCStreamer &Out, ArrayRef<std::string> Inputs) {
   writeIndex(Out, MCOFI.getDwarfCUIndexSection(), ContributionOffsets,
              IndexEntries);
 
-  return Error();
+  return Error::success();
 }
 
 static int error(const Twine &Error, const Twine &Context) {

tools/llvm-nm/llvm-nm.cpp

@@ -1113,7 +1113,7 @@ static void dumpSymbolNamesFromFile(std::string &Filename) {
     }
 
     {
-      Error Err;
+      Error Err = Error::success();
       for (auto &C : A->children(Err)) {
         Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary(&Context);
         if (!ChildOrErr) {
@@ -1178,7 +1178,7 @@ static void dumpSymbolNamesFromFile(std::string &Filename) {
             } else if (Expected<std::unique_ptr<Archive>> AOrErr =
                            I->getAsArchive()) {
               std::unique_ptr<Archive> &A = *AOrErr;
-              Error Err;
+              Error Err = Error::success();
               for (auto &C : A->children(Err)) {
                 Expected<std::unique_ptr<Binary>> ChildOrErr =
                     C.getAsBinary(&Context);
@@ -1249,7 +1249,7 @@ static void dumpSymbolNamesFromFile(std::string &Filename) {
           } else if (Expected<std::unique_ptr<Archive>> AOrErr =
                          I->getAsArchive()) {
             std::unique_ptr<Archive> &A = *AOrErr;
-            Error Err;
+            Error Err = Error::success();
             for (auto &C : A->children(Err)) {
               Expected<std::unique_ptr<Binary>> ChildOrErr =
                   C.getAsBinary(&Context);
@@ -1316,7 +1316,7 @@ static void dumpSymbolNamesFromFile(std::string &Filename) {
       } else if (Expected<std::unique_ptr<Archive>> AOrErr =
                   I->getAsArchive()) {
         std::unique_ptr<Archive> &A = *AOrErr;
-        Error Err;
+        Error Err = Error::success();
         for (auto &C : A->children(Err)) {
           Expected<std::unique_ptr<Binary>> ChildOrErr =
             C.getAsBinary(&Context);

tools/llvm-objdump/MachODump.cpp

@@ -1546,7 +1546,8 @@ static void printArchiveChild(StringRef Filename, const Archive::Child &C,
 static void printArchiveHeaders(StringRef Filename, Archive *A, bool verbose,
                                 bool print_offset,
                                 StringRef ArchitectureName = StringRef()) {
-  Error Err;
+  Error Err = Error::success();
+  ;
   for (const auto &C : A->children(Err, false))
     printArchiveChild(Filename, C, verbose, print_offset, ArchitectureName);
 
@@ -1583,7 +1584,7 @@ void llvm::ParseInputMachO(StringRef Filename) {
     if (ArchiveHeaders)
       printArchiveHeaders(Filename, A, !NonVerbose, ArchiveMemberOffsets);
 
-    Error Err;
+    Error Err = Error::success();
     for (auto &C : A->children(Err)) {
       Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
       if (!ChildOrErr) {
@@ -1641,7 +1642,7 @@ void llvm::ParseInputMachO(StringRef Filename) {
               if (ArchiveHeaders)
                 printArchiveHeaders(Filename, A.get(), !NonVerbose,
                                     ArchiveMemberOffsets, ArchitectureName);
-              Error Err;
+              Error Err = Error::success();
               for (auto &C : A->children(Err)) {
                 Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
                 if (!ChildOrErr) {
@@ -1697,7 +1698,7 @@ void llvm::ParseInputMachO(StringRef Filename) {
             if (ArchiveHeaders)
               printArchiveHeaders(Filename, A.get(), !NonVerbose,
                                   ArchiveMemberOffsets);
-            Error Err;
+            Error Err = Error::success();
             for (auto &C : A->children(Err)) {
               Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
               if (!ChildOrErr) {
@@ -1749,7 +1750,7 @@ void llvm::ParseInputMachO(StringRef Filename) {
         if (ArchiveHeaders)
           printArchiveHeaders(Filename, A.get(), !NonVerbose,
                               ArchiveMemberOffsets, ArchitectureName);
-        Error Err;
+        Error Err = Error::success();
         for (auto &C : A->children(Err)) {
           Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
           if (!ChildOrErr) {

tools/llvm-objdump/llvm-objdump.cpp

@@ -1969,7 +1969,7 @@ static void DumpObject(const COFFImportFile *I, const Archive *A) {
 
 /// @brief Dump each object file in \a a;
 static void DumpArchive(const Archive *a) {
-  Error Err;
+  Error Err = Error::success();
   for (auto &C : a->children(Err)) {
     Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
     if (!ChildOrErr) {

tools/llvm-readobj/llvm-readobj.cpp

@@ -458,7 +458,7 @@ static void dumpObject(const ObjectFile *Obj) {
 
 /// @brief Dumps each object file in \a Arc;
 static void dumpArchive(const Archive *Arc) {
-  Error Err;
+  Error Err = Error::success();
   for (auto &Child : Arc->children(Err)) {
     Expected<std::unique_ptr<Binary>> ChildOrErr = Child.getAsBinary();
     if (!ChildOrErr) {

tools/llvm-size/llvm-size.cpp

@@ -542,7 +542,7 @@ static void printFileSectionSizes(StringRef file) {
 
   if (Archive *a = dyn_cast<Archive>(&Bin)) {
     // This is an archive. Iterate over each member and display its sizes.
-    Error Err;
+    Error Err = Error::success();
     for (auto &C : a->children(Err)) {
       Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
       if (!ChildOrErr) {
@@ -611,7 +611,7 @@ static void printFileSectionSizes(StringRef file) {
               std::unique_ptr<Archive> &UA = *AOrErr;
               // This is an archive. Iterate over each member and display its
               // sizes.
-              Error Err;
+              Error Err = Error::success();
               for (auto &C : UA->children(Err)) {
                 Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
                 if (!ChildOrErr) {
@@ -700,7 +700,7 @@ static void printFileSectionSizes(StringRef file) {
             std::unique_ptr<Archive> &UA = *AOrErr;
             // This is an archive. Iterate over each member and display its
             // sizes.
-            Error Err;
+            Error Err = Error::success();
             for (auto &C : UA->children(Err)) {
               Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
               if (!ChildOrErr) {
@@ -775,7 +775,7 @@ static void printFileSectionSizes(StringRef file) {
                          I->getAsArchive()) {
         std::unique_ptr<Archive> &UA = *AOrErr;
         // This is an archive. Iterate over each member and display its sizes.
-        Error Err;
+        Error Err = Error::success();
         for (auto &C : UA->children(Err)) {
           Expected<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
           if (!ChildOrErr) {

tools/llvm-xray/xray-extract.cc

@@ -223,8 +223,8 @@ void InstrumentationMapExtractor::exportAsYAML(raw_ostream &OS) {
   Out << YAMLSleds;
 }
 
-static CommandRegistration Unused(&Extract, [] {
-  Error Err;
+static CommandRegistration Unused(&Extract, []() -> Error {
+  Error Err = Error::success();
   xray::InstrumentationMapExtractor Extractor(
       ExtractInput, InstrumentationMapExtractor::InputFormats::ELF, Err);
   if (Err)

tools/sancov/sancov.cc

@@ -821,7 +821,7 @@ static void getObjectCoveragePoints(const object::ObjectFile &O,
 static void
 visitObjectFiles(const object::Archive &A,
                  function_ref<void(const object::ObjectFile &)> Fn) {
-  Error Err;
+  Error Err = Error::success();
   for (auto &C : A.children(Err)) {
     Expected<std::unique_ptr<object::Binary>> ChildOrErr = C.getAsBinary();
     failIfError(ChildOrErr);

unittests/Support/ErrorTest.cpp

@@ -82,12 +82,14 @@ protected:
 
 char CustomSubError::ID = 0;
 
-static Error handleCustomError(const CustomError &CE) { return Error(); }
+static Error handleCustomError(const CustomError &CE) {
+  return Error::success();
+}
 
 static void handleCustomErrorVoid(const CustomError &CE) {}
 
 static Error handleCustomErrorUP(std::unique_ptr<CustomError> CE) {
-  return Error();
+  return Error::success();
 }
 
 static void handleCustomErrorUPVoid(std::unique_ptr<CustomError> CE) {}