[llvm-readobj] - Use cantFail() for all `Obj->sections()` calls. NFCI.

[grimar]

Summary

ELFDumper<ELFT>::ELFDumper calls Obj->sections() in its constructor:
https://github.com/llvm/llvm-project/blob/master/llvm/tools/llvm-readobj/ELFDumper.cpp#L2046

this means that all subsequent calls can't fail and can be
wrapped into cantFail in instead of unwrapOrError for simplicity.

Actually we already do it in a few places. In this patch I've fixed all
other places I've found.

[jhenderson]

LGTM!

llvm/tools/llvm-readobj/ELFDumper.cpp

if (!SecOrErr)
     return SecOrErr.takeError();
   return Obj->getSectionName(*SecOrErr);
 }
 
 template <class ELFO>
 static const typename ELFO::Elf_Shdr *
 findNotEmptySectionByAddress(const ELFO *Obj, StringRef FileName,
                              uint64_t Addr) {
-  for (const auto &Shdr : unwrapOrError(FileName, Obj->sections()))
+  for (const typename ELFO::Elf_Shdr &Shdr : cantFail(Obj->sections()))
     if (Shdr.sh_addr == Addr && Shdr.sh_size > 0)
       return &Shdr;
   return nullptr;
 }
 
 template <class ELFO>
 static const typename ELFO::Elf_Shdr *
 findSectionByName(const ELFO &Obj, StringRef FileName, StringRef Name) {
-  for (const auto &Shdr : unwrapOrError(FileName, Obj.sections()))
+  for (const typename ELFO::Elf_Shdr &Shdr : cantFail(Obj.sections()))
     if (Name == unwrapOrError(FileName, Obj.getSectionName(&Shdr)))
       return &Shdr;
   return nullptr;
 }
 
 static const EnumEntry<unsigned> ElfClass[] = {
   {"None",   "none",   ELF::ELFCLASSNONE},
   {"32-bit", "ELF32",  ELF::ELFCLASS32},
for (const Elf_Phdr &Phdr :
     if (Phdr.p_type != ELF::PT_DYNAMIC)
       continue;
     DynamicPhdr = &Phdr;
     break;
   }
 
   // Try to locate the .dynamic section in the sections header table.
   const Elf_Shdr *DynamicSec = nullptr;
-  for (const Elf_Shdr &Sec :
-       unwrapOrError(ObjF->getFileName(), Obj->sections())) {
+  for (const Elf_Shdr &Sec : cantFail(Obj->sections())) {
     if (Sec.sh_type != ELF::SHT_DYNAMIC)
       continue;
     DynamicSec = &Sec;
     break;
   }
 
   if (DynamicPhdr && DynamicPhdr->p_offset + DynamicPhdr->p_filesz >
                          ObjF->getMemoryBufferRef().getBufferSize()) {
ELFDumper<ELFT>::ELFDumper(const object::ELFObjectFile<ELFT> *ObjF,
   };
 
   if (opts::Output == opts::GNU)
     ELFDumperStyle.reset(new GNUStyle<ELFT>(Writer, this));
   else
     ELFDumperStyle.reset(new LLVMStyle<ELFT>(Writer, this));
 
   const ELFFile<ELFT> *Obj = ObjF->getELFFile();
-  typename ELFT::ShdrRange Sections =
-      unwrapOrError(ObjF->getFileName(), Obj->sections());
+  typename ELFT::ShdrRange Sections = cantFail(Obj->sections());
   for (const Elf_Shdr &Sec : Sections) {
     switch (Sec.sh_type) {
     case ELF::SHT_SYMTAB:
       if (!DotSymtabSec)
         DotSymtabSec = &Sec;
       break;
     case ELF::SHT_DYNSYM:
       if (!DynSymRegion) {
if (!Obj->isLE()) {
     return;
   }
 
   const unsigned Machine = Obj->getHeader()->e_machine;
   assert((Machine == EM_ARM || Machine == EM_RISCV) &&
          "Attributes not implemented.");
 
   DictScope BA(W, "BuildAttributes");
-  for (const auto &Sec : unwrapOrError(ObjF->getFileName(), Obj->sections())) {
+  for (const Elf_Shdr &Sec : cantFail(Obj->sections())) {
     if (Sec.sh_type != ELF::SHT_ARM_ATTRIBUTES &&
         Sec.sh_type != ELF::SHT_RISCV_ATTRIBUTES)
       continue;
 
     ArrayRef<uint8_t> Contents =
         unwrapOrError(ObjF->getFileName(), Obj->getSectionContents(&Sec));
     if (Contents[0] != ELFAttrs::Format_Version) {
       reportWarning(createError(Twine("unrecognised FormatVersion: 0x") +
while (!Sec.empty()) {
     }
     Sec = Sec.slice(O->size);
   }
 }
 
 template <class ELFT> void ELFDumper<ELFT>::printStackMap() const {
   const ELFFile<ELFT> *Obj = ObjF->getELFFile();
   const Elf_Shdr *StackMapSection = nullptr;
-  for (const auto &Sec : unwrapOrError(ObjF->getFileName(), Obj->sections())) {
+  for (const Elf_Shdr &Sec : cantFail(Obj->sections())) {
     StringRef Name =
         unwrapOrError(ObjF->getFileName(), Obj->getSectionName(&Sec));
     if (Name == ".llvm_stackmaps") {
       StackMapSection = &Sec;
       break;
     }
   }
 

 
 template <class ELFT>
 static std::string getSectionHeadersNumString(const ELFFile<ELFT> *Obj,
                                               StringRef FileName) {
   const typename ELFT::Ehdr *ElfHeader = Obj->getHeader();
   if (ElfHeader->e_shnum != 0)
     return to_string(ElfHeader->e_shnum);
 
-  ArrayRef<typename ELFT::Shdr> Arr = unwrapOrError(FileName, Obj->sections());
+  ArrayRef<typename ELFT::Shdr> Arr = cantFail(Obj->sections());
   if (Arr.empty())
     return "0";
   return "0 (" + to_string(Arr[0].sh_size) + ")";
 }
 
 template <class ELFT>
 static std::string getSectionHeaderTableIndexString(const ELFFile<ELFT> *Obj,
                                                     StringRef FileName) {
   const typename ELFT::Ehdr *ElfHeader = Obj->getHeader();
   if (ElfHeader->e_shstrndx != SHN_XINDEX)
     return to_string(ElfHeader->e_shstrndx);
 
-  ArrayRef<typename ELFT::Shdr> Arr = unwrapOrError(FileName, Obj->sections());
+  ArrayRef<typename ELFT::Shdr> Arr = cantFail(Obj->sections());
   if (Arr.empty())
     return "65535 (corrupt: out of range)";
   return to_string(ElfHeader->e_shstrndx) + " (" + to_string(Arr[0].sh_link) +
          ")";
 }
 
 template <class ELFT> void GNUStyle<ELFT>::printFileHeaders(const ELFO *Obj) {
   const Elf_Ehdr *e = Obj->getHeader();

 std::vector<GroupSection> getGroups(const ELFFile<ELFT> *Obj,
                                     StringRef FileName) {
   using Elf_Shdr = typename ELFT::Shdr;
   using Elf_Sym = typename ELFT::Sym;
   using Elf_Word = typename ELFT::Word;
 
   std::vector<GroupSection> Ret;
   uint64_t I = 0;
-  for (const Elf_Shdr &Sec : unwrapOrError(FileName, Obj->sections())) {
+  for (const Elf_Shdr &Sec : cantFail(Obj->sections())) {
     ++I;
     if (Sec.sh_type != ELF::SHT_GROUP)
       continue;
 
     const Elf_Shdr *Symtab =
         unwrapOrError(FileName, Obj->getSection(Sec.sh_link));
     StringRef StrTable =
         unwrapOrError(FileName, Obj->getStringTableForSymtab(*Symtab));
else
     OS << "     Info    Type                Sym. Value  Symbol's Name";
   if (IsRela)
     OS << " + Addend";
   OS << "\n";
 }
 
 template <class ELFT> void GNUStyle<ELFT>::printRelocations(const ELFO *Obj) {
   bool HasRelocSections = false;
-  for (const Elf_Shdr &Sec : unwrapOrError(this->FileName, Obj->sections())) {
+  for (const Elf_Shdr &Sec : cantFail(Obj->sections())) {
     if (Sec.sh_type != ELF::SHT_REL && Sec.sh_type != ELF::SHT_RELA &&
         Sec.sh_type != ELF::SHT_RELR && Sec.sh_type != ELF::SHT_ANDROID_REL &&
         Sec.sh_type != ELF::SHT_ANDROID_RELA &&
         Sec.sh_type != ELF::SHT_ANDROID_RELR)
       continue;
     HasRelocSections = true;
     StringRef Name = unwrapOrError(this->FileName, Obj->getSectionName(&Sec));
     unsigned Entries = Sec.getEntityCount();
else
     OS << "  ";
 
   OS << "p (processor specific)\n";
 }
 
 template <class ELFT>
 void GNUStyle<ELFT>::printSectionHeaders(const ELFO *Obj) {
   unsigned Bias = ELFT::Is64Bits ? 0 : 8;
-  ArrayRef<Elf_Shdr> Sections = unwrapOrError(this->FileName, Obj->sections());
+  ArrayRef<Elf_Shdr> Sections = cantFail(Obj->sections());
   OS << "There are " << to_string(Sections.size())
      << " section headers, starting at offset "
      << "0x" << to_hexString(Obj->getHeader()->e_shoff, false) << ":\n\n";
   OS << "Section Headers:\n";
   Field Fields[11] = {
       {"[Nr]", 2},        {"Name", 7},        {"Type", 25},
       {"Address", 41},    {"Off", 58 - Bias}, {"Size", 65 - Bias},
       {"ES", 72 - Bias},  {"Flg", 75 - Bias}, {"Lk", 79 - Bias},
void GNUStyle<ELFT>::printSectionMapping(const ELFO *Obj) {
   OS << "\n Section to Segment mapping:\n  Segment Sections...\n";
   DenseSet<const Elf_Shdr *> BelongsToSegment;
   int Phnum = 0;
   for (const Elf_Phdr &Phdr :
        unwrapOrError(this->FileName, Obj->program_headers())) {
     std::string Sections;
     OS << format("   %2.2d     ", Phnum++);
     // Check if each section is in a segment and then print mapping.
-    for (const Elf_Shdr &Sec : unwrapOrError(this->FileName, Obj->sections())) {
+    for (const Elf_Shdr &Sec : cantFail(Obj->sections())) {
       if (Sec.sh_type == ELF::SHT_NULL)
         continue;
 
       // readelf additionally makes sure it does not print zero sized sections
       // at end of segments and for PT_DYNAMIC both start and end of section
       // .tbss must only be shown in PT_TLS section.
       if (checkTLSSections<ELFT>(Phdr, Sec) && checkOffsets<ELFT>(Phdr, Sec) &&
           checkVMA<ELFT>(Phdr, Sec) && checkPTDynamic<ELFT>(Phdr, Sec)) {
         Sections +=
             unwrapOrError(this->FileName, Obj->getSectionName(&Sec)).str() +
             " ";
         BelongsToSegment.insert(&Sec);
       }
     }
     OS << Sections << "\n";
     OS.flush();
   }
 
   // Display sections that do not belong to a segment.
   std::string Sections;
-  for (const Elf_Shdr &Sec : unwrapOrError(this->FileName, Obj->sections())) {
+  for (const Elf_Shdr &Sec : cantFail(Obj->sections())) {
     if (BelongsToSegment.find(&Sec) == BelongsToSegment.end())
       Sections +=
           unwrapOrError(this->FileName, Obj->getSectionName(&Sec)).str() + ' ';
   }
   if (!Sections.empty()) {
     OS << "   None  " << Sections << '\n';
     OS.flush();
   }
auto ProcessNote = [&](const Elf_Note &Note) {
     } else if (!Descriptor.empty()) {
       OS << "   description data:";
       for (uint8_t B : Descriptor)
         OS << " " << format("%02x", B);
       OS << '\n';
     }
   };
 
-  ArrayRef<Elf_Shdr> Sections = unwrapOrError(this->FileName, Obj->sections());
+  ArrayRef<Elf_Shdr> Sections = cantFail(Obj->sections());
   if (Obj->getHeader()->e_type != ELF::ET_CORE && !Sections.empty()) {
     for (const auto &S : Sections) {
       if (S.sh_type != SHT_NOTE)
         continue;
       PrintHeader(expectedToOptional(Obj->getSectionName(&S)), S.sh_offset,
                   S.sh_size);
       Error Err = Error::success();
       for (auto Note : Obj->notes(S, Err))
void DumpStyle<ELFT>::printDependentLibsHelper(
     function_ref<void(StringRef, uint64_t)> OnLibEntry) {
   auto Warn = [this](unsigned SecNdx, StringRef Msg) {
     this->reportUniqueWarning(
         createError("SHT_LLVM_DEPENDENT_LIBRARIES section at index " +
                     Twine(SecNdx) + " is broken: " + Msg));
   };
 
   unsigned I = -1;
-  for (const Elf_Shdr &Shdr : unwrapOrError(this->FileName, Obj->sections())) {
+  for (const Elf_Shdr &Shdr : cantFail(Obj->sections())) {
     ++I;
     if (Shdr.sh_type != ELF::SHT_LLVM_DEPENDENT_LIBRARIES)
       continue;
 
     OnSectionStart(Shdr);
 
     Expected<ArrayRef<uint8_t>> ContentsOrErr = Obj->getSectionContents(&Shdr);
     if (!ContentsOrErr) {
void LLVMStyle<ELFT>::printGroupSections(const ELFO *Obj) {
   if (V.empty())
     W.startLine() << "There are no group sections in the file.\n";
 }
 
 template <class ELFT> void LLVMStyle<ELFT>::printRelocations(const ELFO *Obj) {
   ListScope D(W, "Relocations");
 
   int SectionNumber = -1;
-  for (const Elf_Shdr &Sec : unwrapOrError(this->FileName, Obj->sections())) {
+  for (const Elf_Shdr &Sec : cantFail(Obj->sections())) {
     ++SectionNumber;
 
     if (Sec.sh_type != ELF::SHT_REL && Sec.sh_type != ELF::SHT_RELA &&
         Sec.sh_type != ELF::SHT_RELR && Sec.sh_type != ELF::SHT_ANDROID_REL &&
         Sec.sh_type != ELF::SHT_ANDROID_RELA &&
         Sec.sh_type != ELF::SHT_ANDROID_RELR)
       continue;
 
void LLVMStyle<ELFT>::printRelocation(const ELFO *Obj, unsigned SecIndex,
   }
 }
 
 template <class ELFT>
 void LLVMStyle<ELFT>::printSectionHeaders(const ELFO *Obj) {
   ListScope SectionsD(W, "Sections");
 
   int SectionIndex = -1;
-  ArrayRef<Elf_Shdr> Sections = unwrapOrError(this->FileName, Obj->sections());
   std::vector<EnumEntry<unsigned>> FlagsList =
       getSectionFlagsForTarget(Obj->getHeader()->e_machine);
-  for (const Elf_Shdr &Sec : Sections) {
+  for (const Elf_Shdr &Sec : cantFail(Obj->sections())) {
     StringRef Name = "<?>";
     if (Expected<StringRef> SecNameOrErr =
             Obj->getSectionName(&Sec, this->dumper()->WarningHandler))
       Name = *SecNameOrErr;
     else
       this->reportUniqueWarning(SecNameOrErr.takeError());
 
     DictScope SectionD(W, "Section");
if (Name == "GNU") {
         else
           reportWarning(Note.takeError(), this->FileName);
       }
     } else if (!Descriptor.empty()) {
       W.printBinaryBlock("Description data", Descriptor);
     }
   };
 
-  ArrayRef<Elf_Shdr> Sections = unwrapOrError(this->FileName, Obj->sections());
+  ArrayRef<Elf_Shdr> Sections = cantFail(Obj->sections());
   if (Obj->getHeader()->e_type != ELF::ET_CORE && !Sections.empty()) {
     for (const auto &S : Sections) {
       if (S.sh_type != SHT_NOTE)
         continue;
       DictScope D(W, "NoteSection");
       PrintHeader(expectedToOptional(Obj->getSectionName(&S)), S.sh_offset,
                   S.sh_size);
       Error Err = Error::success();
void LLVMStyle<ELFT>::printNotes(const ELFFile<ELFT> *Obj) {
   }
 }
 
 template <class ELFT>
 void LLVMStyle<ELFT>::printELFLinkerOptions(const ELFFile<ELFT> *Obj) {
   ListScope L(W, "LinkerOptions");
 
   unsigned I = -1;
-  for (const Elf_Shdr &Shdr : unwrapOrError(this->FileName, Obj->sections())) {
+  for (const Elf_Shdr &Shdr : cantFail(Obj->sections())) {
     ++I;
     if (Shdr.sh_type != ELF::SHT_LLVM_LINKER_OPTIONS)
       continue;
 
     ArrayRef<uint8_t> Contents =
         unwrapOrError(this->FileName, Obj->getSectionContents(&Shdr));
     if (Contents.empty())
       continue;