[llvm/Object] - Convert SectionRef::getName() to return Expected<>

SectionRef::getName() returns std::error_code now.
Returning Expected<> instead has multiple benefits.

For example, it forces user to check the error returned.
Also Expected<> may keep a valuable string error message,
what is more useful than having a error code.
(Object\invalid.test was updated to show the new messages printed.)

This patch makes a change for all users to switch to Expected<> version.

Note: in a few places the error returned was ignored before my changes.
In such places I left them ignored. My intention was to convert the interface
used, and not to improve and/or the existent users in this patch.
(Though I think this is good idea for a follow-ups to revisit such places
and either remove consumeError calls or comment each of them to clarify why
it is OK to have them).

Differential revision: https://reviews.llvm.org/D66089

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@368812 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Object/ELFObjectFile.h

@@ -461,13 +461,15 @@ Expected<StringRef> ELFObjectFile<ELFT>::getSymbolName(DataRefImpl Sym) const {
   if (!SymStrTabOrErr)
     return SymStrTabOrErr.takeError();
   Expected<StringRef> Name = ESym->getName(*SymStrTabOrErr);
+  if (Name && !Name->empty())
+    return Name;
 
   // If the symbol name is empty use the section name.
-  if ((!Name || Name->empty()) && ESym->getType() == ELF::STT_SECTION) {
-    StringRef SecName;
-    Expected<section_iterator> Sec = getSymbolSection(Sym);
-    if (Sec && !(*Sec)->getName(SecName))
-      return SecName;
+  if (ESym->getType() == ELF::STT_SECTION) {
+    if (Expected<section_iterator> SecOrErr = getSymbolSection(Sym)) {
+      consumeError(Name.takeError());
+      return (*SecOrErr)->getName();
+    }
   }
   return Name;
 }

include/llvm/Object/ObjectFile.h

@@ -94,7 +94,7 @@ class SectionRef {
 
   void moveNext();
 
-  std::error_code getName(StringRef &Result) const;
+  Expected<StringRef> getName() const;
   uint64_t getAddress() const;
   uint64_t getIndex() const;
   uint64_t getSize() const;
@@ -434,12 +434,8 @@ inline void SectionRef::moveNext() {
   return OwningObject->moveSectionNext(SectionPimpl);
 }
 
-inline std::error_code SectionRef::getName(StringRef &Result) const {
-  Expected<StringRef> NameOrErr = OwningObject->getSectionName(SectionPimpl);
-  if (!NameOrErr)
-    return errorToErrorCode(NameOrErr.takeError());
-  Result = *NameOrErr;
-  return std::error_code();
+inline Expected<StringRef> SectionRef::getName() const {
+  return OwningObject->getSectionName(SectionPimpl);
 }
 
 inline uint64_t SectionRef::getAddress() const {

lib/DebugInfo/DWARF/DWARFContext.cpp

@@ -1506,7 +1506,11 @@ class DWARFObjInMemory final : public DWARFObject {
     StringMap<unsigned> SectionAmountMap;
     for (const SectionRef &Section : Obj.sections()) {
       StringRef Name;
-      Section.getName(Name);
+      if (auto NameOrErr = Section.getName())
+        Name = *NameOrErr;
+      else
+        consumeError(NameOrErr.takeError());
+
       ++SectionAmountMap[Name];
       SectionNames.push_back({ Name, true });
 
@@ -1571,12 +1575,15 @@ class DWARFObjInMemory final : public DWARFObject {
         continue;
 
       StringRef RelSecName;
-      StringRef RelSecData;
-      RelocatedSection->getName(RelSecName);
+      if (auto NameOrErr = RelocatedSection->getName())
+        RelSecName = *NameOrErr;
+      else
+        consumeError(NameOrErr.takeError());
 
       // If the section we're relocating was relocated already by the JIT,
       // then we used the relocated version above, so we do not need to process
       // relocations for it now.
+      StringRef RelSecData;
       if (L && L->getLoadedSectionContents(*RelocatedSection, RelSecData))
         continue;
 

lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp

@@ -54,10 +54,11 @@ SymbolizableObjectFile::create(const object::ObjectFile *Obj,
   // PowerPC64 ELF.
   if (Obj->getArch() == Triple::ppc64) {
     for (section_iterator Section : Obj->sections()) {
-      StringRef Name;
-      if (auto EC = Section->getName(Name))
-        return EC;
-      if (Name == ".opd") {
+      Expected<StringRef> NameOrErr = Section->getName();
+      if (!NameOrErr)
+        return errorToErrorCode(NameOrErr.takeError());
+
+      if (*NameOrErr == ".opd") {
         Expected<StringRef> E = Section->getContents();
         if (!E)
           return errorToErrorCode(E.takeError());

lib/DebugInfo/Symbolize/Symbolize.cpp

@@ -259,7 +259,11 @@ bool getGNUDebuglinkContents(const ObjectFile *Obj, std::string &DebugName,
     return false;
   for (const SectionRef &Section : Obj->sections()) {
     StringRef Name;
-    Section.getName(Name);
+    if (Expected<StringRef> NameOrErr = Section.getName())
+      Name = *NameOrErr;
+    else
+      consumeError(NameOrErr.takeError());
+
     Name = Name.substr(Name.find_first_not_of("._"));
     if (Name == "gnu_debuglink") {
       Expected<StringRef> ContentsOrErr = Section.getContents();

lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.cpp

@@ -96,9 +96,10 @@ Error MachOAtomGraphBuilder::parseSections() {
     assert((SecRef.getAlignment() <= std::numeric_limits<uint32_t>::max()) &&
            "Section alignment does not fit in 32 bits");
 
-    StringRef Name;
-    if (auto EC = SecRef.getName(Name))
-      return errorCodeToError(EC);
+    Expected<StringRef> NameOrErr = SecRef.getName();
+    if (!NameOrErr)
+      return NameOrErr.takeError();
+    StringRef Name = *NameOrErr;
 
     unsigned SectionIndex = SecRef.getIndex() + 1;
 

lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp

@@ -535,9 +535,10 @@ Error RuntimeDyldImpl::computeTotalAllocSize(const ObjectFile &Obj,
       bool IsCode = Section.isText();
       bool IsReadOnly = isReadOnlyData(Section);
 
-      StringRef Name;
-      if (auto EC = Section.getName(Name))
-        return errorCodeToError(EC);
+      Expected<StringRef> NameOrErr = Section.getName();
+      if (!NameOrErr)
+        return NameOrErr.takeError();
+      StringRef Name = *NameOrErr;
 
       uint64_t StubBufSize = computeSectionStubBufSize(Obj, Section);
 
@@ -777,9 +778,10 @@ RuntimeDyldImpl::emitSection(const ObjectFile &Obj,
   // anyway, so we should guarantee that the alignment is always at least 1.
   Alignment = std::max(1u, Alignment);
 
-  StringRef Name;
-  if (auto EC = Section.getName(Name))
-    return errorCodeToError(EC);
+  Expected<StringRef> NameOrErr = Section.getName();
+  if (!NameOrErr)
+    return NameOrErr.takeError();
+  StringRef Name = *NameOrErr;
 
   StubBufSize = computeSectionStubBufSize(Obj, Section);
 

lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp

@@ -160,9 +160,13 @@ createRTDyldELFObject(MemoryBufferRef Buffer, const ObjectFile &SourceObject,
   // Iterate over all sections in the object.
   auto SI = SourceObject.section_begin();
   for (const auto &Sec : Obj->sections()) {
-    StringRef SectionName;
-    Sec.getName(SectionName);
-    if (SectionName != "") {
+    Expected<StringRef> NameOrErr = Sec.getName();
+    if (!NameOrErr) {
+      consumeError(NameOrErr.takeError());
+      continue;
+    }
+
+    if (*NameOrErr != "") {
       DataRefImpl ShdrRef = Sec.getRawDataRefImpl();
       Elf_Shdr *shdr = const_cast<Elf_Shdr *>(
           reinterpret_cast<const Elf_Shdr *>(ShdrRef.p));
@@ -567,10 +571,11 @@ Error RuntimeDyldELF::findPPC64TOCSection(const ELFObjectFileBase &Obj,
 
   // The TOC consists of sections .got, .toc, .tocbss, .plt in that
   // order. The TOC starts where the first of these sections starts.
-  for (auto &Section: Obj.sections()) {
-    StringRef SectionName;
-    if (auto EC = Section.getName(SectionName))
-      return errorCodeToError(EC);
+  for (auto &Section : Obj.sections()) {
+    Expected<StringRef> NameOrErr = Section.getName();
+    if (!NameOrErr)
+      return NameOrErr.takeError();
+    StringRef SectionName = *NameOrErr;
 
     if (SectionName == ".got"
         || SectionName == ".toc"
@@ -605,9 +610,10 @@ Error RuntimeDyldELF::findOPDEntrySection(const ELFObjectFileBase &Obj,
     if (RelSecI == Obj.section_end())
       continue;
 
-    StringRef RelSectionName;
-    if (auto EC = RelSecI->getName(RelSectionName))
-      return errorCodeToError(EC);
+    Expected<StringRef> NameOrErr = RelSecI->getName();
+    if (!NameOrErr)
+      return NameOrErr.takeError();
+    StringRef RelSectionName = *NameOrErr;
 
     if (RelSectionName != ".opd")
       continue;
@@ -1879,8 +1885,14 @@ Error RuntimeDyldELF::finalizeLoad(const ObjectFile &Obj,
   ObjSectionToIDMap::iterator i, e;
   for (i = SectionMap.begin(), e = SectionMap.end(); i != e; ++i) {
     const SectionRef &Section = i->first;
+
     StringRef Name;
-    Section.getName(Name);
+    Expected<StringRef> NameOrErr = Section.getName();
+    if (NameOrErr)
+      Name = *NameOrErr;
+    else
+      consumeError(NameOrErr.takeError());
+
     if (Name == ".eh_frame") {
       UnregisteredEHFrameSections.push_back(i->second);
       break;

lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp

@@ -233,7 +233,10 @@ RuntimeDyldMachOCRTPBase<Impl>::finalizeLoad(const ObjectFile &Obj,
 
   for (const auto &Section : Obj.sections()) {
     StringRef Name;
-    Section.getName(Name);
+    if (Expected<StringRef> NameOrErr = Section.getName())
+      Name = *NameOrErr;
+    else
+      consumeError(NameOrErr.takeError());
 
     // Force emission of the __text, __eh_frame, and __gcc_except_tab sections
     // if they're present. Otherwise call down to the impl to handle other

lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldCOFFX86_64.h

@@ -284,14 +284,14 @@ class RuntimeDyldCOFFX86_64 : public RuntimeDyldCOFF {
     // Look for and record the EH frame section IDs.
     for (const auto &SectionPair : SectionMap) {
       const object::SectionRef &Section = SectionPair.first;
-      StringRef Name;
-      if (auto EC = Section.getName(Name))
-        return errorCodeToError(EC);
+      Expected<StringRef> NameOrErr = Section.getName();
+      if (!NameOrErr)
+        return NameOrErr.takeError();
 
       // Note unwind info is stored in .pdata but often points to .xdata
       // with an IMAGE_REL_AMD64_ADDR32NB relocation. Using a memory manager
       // that keeps sections ordered in relation to __ImageBase is necessary.
-      if (Name == ".pdata")
+      if ((*NameOrErr) == ".pdata")
         UnregisteredEHFrameSections.push_back(SectionPair.second);
     }
     return Error::success();

lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOARM.h

@@ -289,7 +289,10 @@ class RuntimeDyldMachOARM
   Error finalizeSection(const ObjectFile &Obj, unsigned SectionID,
                        const SectionRef &Section) {
     StringRef Name;
-    Section.getName(Name);
+    if (Expected<StringRef> NameOrErr = Section.getName())
+      Name = *NameOrErr;
+    else
+      consumeError(NameOrErr.takeError());
 
     if (Name == "__nl_symbol_ptr")
       return populateIndirectSymbolPointersSection(cast<MachOObjectFile>(Obj),

lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOI386.h

@@ -128,7 +128,10 @@ class RuntimeDyldMachOI386
   Error finalizeSection(const ObjectFile &Obj, unsigned SectionID,
                        const SectionRef &Section) {
     StringRef Name;
-    Section.getName(Name);
+    if (Expected<StringRef> NameOrErr = Section.getName())
+      Name = *NameOrErr;
+    else
+      consumeError(NameOrErr.takeError());
 
     if (Name == "__jump_table")
       return populateJumpTable(cast<MachOObjectFile>(Obj), Section, SectionID);

lib/Object/COFFObjectFile.cpp

@@ -994,11 +994,12 @@ std::error_code COFFObjectFile::getSection(int32_t Index,
 std::error_code COFFObjectFile::getSection(StringRef SectionName,
                                            const coff_section *&Result) const {
   Result = nullptr;
-  StringRef SecName;
   for (const SectionRef &Section : sections()) {
-    if (std::error_code E = Section.getName(SecName))
-      return E;
-    if (SecName == SectionName) {
+    auto NameOrErr = Section.getName();
+    if (!NameOrErr)
+      return errorToErrorCode(NameOrErr.takeError());
+
+    if (*NameOrErr == SectionName) {
       Result = getCOFFSection(Section);
       return std::error_code();
     }

lib/Object/Decompressor.cpp

@@ -77,10 +77,15 @@ bool Decompressor::isGnuStyle(StringRef Name) {
 }
 
 bool Decompressor::isCompressed(const object::SectionRef &Section) {
-  StringRef Name;
-  if (Section.getName(Name))
-    return false;
-  return Section.isCompressed() || isGnuStyle(Name);
+  if (Section.isCompressed())
+    return true;
+
+  Expected<StringRef> SecNameOrErr = Section.getName();
+  if (SecNameOrErr)
+    return isGnuStyle(*SecNameOrErr);
+
+  consumeError(SecNameOrErr.takeError());
+  return false;
 }
 
 bool Decompressor::isCompressedELFSection(uint64_t Flags, StringRef Name) {

lib/Object/ELFObjectFile.cpp

@@ -392,9 +392,13 @@ ELFObjectFileBase::getPltAddresses() const {
     return {};
   Optional<SectionRef> Plt = None, RelaPlt = None, GotPlt = None;
   for (const SectionRef &Section : sections()) {
-    StringRef Name;
-    if (Section.getName(Name))
+    Expected<StringRef> NameOrErr = Section.getName();
+    if (!NameOrErr) {
+      consumeError(NameOrErr.takeError());
       continue;
+    }
+    StringRef Name = *NameOrErr;
+
     if (Name == ".plt")
       Plt = Section;
     else if (Name == ".rela.plt" || Name == ".rel.plt")

lib/Object/MachOObjectFile.cpp

@@ -1986,13 +1986,12 @@ Expected<SectionRef> MachOObjectFile::getSection(unsigned SectionIndex) const {
 }
 
 Expected<SectionRef> MachOObjectFile::getSection(StringRef SectionName) const {
-  StringRef SecName;
   for (const SectionRef &Section : sections()) {
-    if (std::error_code E = Section.getName(SecName))
-      return errorCodeToError(E);
-    if (SecName == SectionName) {
+    auto NameOrErr = Section.getName();
+    if (!NameOrErr)
+      return NameOrErr.takeError();
+    if (*NameOrErr == SectionName)
       return Section;
-    }
   }
   return errorCodeToError(object_error::parse_failed);
 }
@@ -3995,7 +3994,11 @@ BindRebaseSegInfo::BindRebaseSegInfo(const object::MachOObjectFile *Obj) {
   uint64_t CurSegAddress;
   for (const SectionRef &Section : Obj->sections()) {
     SectionInfo Info;
-    Section.getName(Info.SectionName);
+    Expected<StringRef> NameOrErr = Section.getName();
+    if (!NameOrErr)
+      consumeError(NameOrErr.takeError());
+    else
+      Info.SectionName = *NameOrErr;
     Info.Address = Section.getAddress();
     Info.Size = Section.getSize();
     Info.SegmentName =

lib/Object/Object.cpp

@@ -251,10 +251,10 @@ void LLVMMoveToNextSymbol(LLVMSymbolIteratorRef SI) {
 
 // SectionRef accessors
 const char *LLVMGetSectionName(LLVMSectionIteratorRef SI) {
-  StringRef ret;
-  if (std::error_code ec = (*unwrap(SI))->getName(ret))
-   report_fatal_error(ec.message());
-  return ret.data();
+  auto NameOrErr = (*unwrap(SI))->getName();
+  if (!NameOrErr)
+    report_fatal_error(NameOrErr.takeError());
+  return NameOrErr->data();
 }
 
 uint64_t LLVMGetSectionSize(LLVMSectionIteratorRef SI) {

lib/ProfileData/Coverage/CoverageMappingReader.cpp

@@ -666,11 +666,11 @@ static Expected<SectionRef> lookupSection(ObjectFile &OF, StringRef Name) {
   };
   Name = stripSuffix(Name);
 
-  StringRef FoundName;
   for (const auto &Section : OF.sections()) {
-    if (auto EC = Section.getName(FoundName))
-      return errorCodeToError(EC);
-    if (stripSuffix(FoundName) == Name)
+    Expected<StringRef> NameOrErr = Section.getName();
+    if (!NameOrErr)
+      return NameOrErr.takeError();
+    if (stripSuffix(*NameOrErr) == Name)
       return Section;
   }
   return make_error<CoverageMapError>(coveragemap_error::no_data_found);

lib/XRay/InstrumentationMap.cpp

@@ -67,10 +67,11 @@ loadObj(StringRef Filename, object::OwningBinary<object::ObjectFile> &ObjFile,
   StringRef Contents = "";
   const auto &Sections = ObjFile.getBinary()->sections();
   auto I = llvm::find_if(Sections, [&](object::SectionRef Section) {
-    StringRef Name = "";
-    if (Section.getName(Name))
-      return false;
-    return Name == "xray_instr_map";
+    Expected<StringRef> NameOrErr = Section.getName();
+    if (NameOrErr)
+      return *NameOrErr == "xray_instr_map";
+    consumeError(NameOrErr.takeError());
+    return false;
   });
 
   if (I == Sections.end())