[lld] r262626 - Simplify error handling.

Rui Ueyama via llvm-commits llvm-commits at lists.llvm.org
Thu Mar 3 12:25:53 PST 2016


Nice change. Do you think that fatal is an appropriate name for that
function? I guess I'd probably name this "check" or something if we didn't
have "fatal" function before.

On Thu, Mar 3, 2016 at 8:21 AM, Rafael Espindola via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: rafael
> Date: Thu Mar  3 10:21:44 2016
> New Revision: 262626
>
> URL: http://llvm.org/viewvc/llvm-project?rev=262626&view=rev
> Log:
> Simplify error handling.
>
> This makes fatal return T when there is no error. This avoids the need
> for quite a few temporaries.
>
> Modified:
>     lld/trunk/ELF/Driver.cpp
>     lld/trunk/ELF/Error.cpp
>     lld/trunk/ELF/Error.h
>     lld/trunk/ELF/InputFiles.cpp
>     lld/trunk/ELF/InputSection.cpp
>     lld/trunk/ELF/SymbolTable.cpp
>     lld/trunk/ELF/Writer.cpp
>
> Modified: lld/trunk/ELF/Driver.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Driver.cpp?rev=262626&r1=262625&r2=262626&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Driver.cpp (original)
> +++ lld/trunk/ELF/Driver.cpp Thu Mar  3 10:21:44 2016
> @@ -70,17 +70,18 @@ static std::pair<ELFKind, uint16_t> pars
>  // Returns slices of MB by parsing MB as an archive file.
>  // Each slice consists of a member file in the archive.
>  static std::vector<MemoryBufferRef> getArchiveMembers(MemoryBufferRef MB)
> {
> -  ErrorOr<std::unique_ptr<Archive>> FileOrErr = Archive::create(MB);
> -  fatal(FileOrErr, "Failed to parse archive");
> -  std::unique_ptr<Archive> File = std::move(*FileOrErr);
> +  std::unique_ptr<Archive> File =
> +      fatal(Archive::create(MB), "Failed to parse archive");
>
>    std::vector<MemoryBufferRef> V;
> -  for (const ErrorOr<Archive::Child> &C : File->children()) {
> -    fatal(C, "Could not get the child of the archive " +
> File->getFileName());
> -    ErrorOr<MemoryBufferRef> MbOrErr = C->getMemoryBufferRef();
> -    fatal(MbOrErr, "Could not get the buffer for a child of the archive "
> +
> -                       File->getFileName());
> -    V.push_back(*MbOrErr);
> +  for (const ErrorOr<Archive::Child> &COrErr : File->children()) {
> +    Archive::Child C = fatal(COrErr, "Could not get the child of the
> archive " +
> +                                         File->getFileName());
> +    MemoryBufferRef Mb =
> +        fatal(C.getMemoryBufferRef(),
> +              "Could not get the buffer for a child of the archive " +
> +                  File->getFileName());
> +    V.push_back(Mb);
>    }
>    return V;
>  }
>
> Modified: lld/trunk/ELF/Error.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Error.cpp?rev=262626&r1=262625&r2=262626&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Error.cpp (original)
> +++ lld/trunk/ELF/Error.cpp Thu Mar  3 10:21:44 2016
> @@ -50,6 +50,10 @@ void fatal(const Twine &Msg) {
>    exit(1);
>  }
>
> +void fatal(const Twine &Msg, const Twine &Prefix) {
> +  fatal(Prefix + ": " + Msg);
> +}
> +
>

This new function seems to be used only once in Error.cpp. You can remove
this if you update the caller to use +.

 void fatal(std::error_code EC, const Twine &Prefix) {
>    if (EC)
>      fatal(Prefix + ": " + EC.message());
>
> Modified: lld/trunk/ELF/Error.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Error.h?rev=262626&r1=262625&r2=262626&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Error.h (original)
> +++ lld/trunk/ELF/Error.h Thu Mar  3 10:21:44 2016
> @@ -38,14 +38,21 @@ template <typename T> bool error(const E
>  }
>
>  LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &Msg);
> +LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &Msg, const Twine &Prefix);
>  void fatal(std::error_code EC, const Twine &Prefix);
>  void fatal(std::error_code EC);
>
> -template <typename T> void fatal(const ErrorOr<T> &V, const Twine
> &Prefix) {
> -  fatal(V.getError(), Prefix);
> +template <class T> T fatal(ErrorOr<T> EO) {
> +  if (EO)
> +    return std::move(*EO);
> +  fatal(EO.getError().message());
>  }
>
> -template <typename T> void fatal(const ErrorOr<T> &V) {
> fatal(V.getError()); }
> +template <class T> T fatal(ErrorOr<T> EO, const Twine &Prefix) {
> +  if (EO)
> +    return std::move(*EO);
> +  fatal(EO.getError().message(), Prefix);
> +}
>
>  } // namespace elf
>  } // namespace lld
>
> Modified: lld/trunk/ELF/InputFiles.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.cpp?rev=262626&r1=262625&r2=262626&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/InputFiles.cpp (original)
> +++ lld/trunk/ELF/InputFiles.cpp Thu Mar  3 10:21:44 2016
> @@ -73,9 +73,7 @@ uint32_t ELFFileBase<ELFT>::getSectionIn
>  template <class ELFT> void ELFFileBase<ELFT>::initStringTable() {
>    if (!Symtab)
>      return;
> -  ErrorOr<StringRef> StringTableOrErr =
> ELFObj.getStringTableForSymtab(*Symtab);
> -  fatal(StringTableOrErr);
> -  StringTable = *StringTableOrErr;
> +  StringTable = fatal(ELFObj.getStringTableForSymtab(*Symtab));
>  }
>
>  template <class ELFT>
> @@ -124,26 +122,19 @@ template <class ELFT>
>  StringRef elf::ObjectFile<ELFT>::getShtGroupSignature(const Elf_Shdr
> &Sec) {
>    const ELFFile<ELFT> &Obj = this->ELFObj;
>    uint32_t SymtabdSectionIndex = Sec.sh_link;
> -  ErrorOr<const Elf_Shdr *> SecOrErr =
> Obj.getSection(SymtabdSectionIndex);
> -  fatal(SecOrErr);
> -  const Elf_Shdr *SymtabSec = *SecOrErr;
> +  const Elf_Shdr *SymtabSec = fatal(Obj.getSection(SymtabdSectionIndex));
>    uint32_t SymIndex = Sec.sh_info;
>    const Elf_Sym *Sym = Obj.getSymbol(SymtabSec, SymIndex);
> -  ErrorOr<StringRef> StringTableOrErr =
> Obj.getStringTableForSymtab(*SymtabSec);
> -  fatal(StringTableOrErr);
> -  ErrorOr<StringRef> SignatureOrErr = Sym->getName(*StringTableOrErr);
> -  fatal(SignatureOrErr);
> -  return *SignatureOrErr;
> +  StringRef StringTable = fatal(Obj.getStringTableForSymtab(*SymtabSec));
> +  return fatal(Sym->getName(StringTable));
>  }
>
>  template <class ELFT>
>  ArrayRef<typename elf::ObjectFile<ELFT>::uint32_X>
>  elf::ObjectFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
>    const ELFFile<ELFT> &Obj = this->ELFObj;
> -  ErrorOr<ArrayRef<uint32_X>> EntriesOrErr =
> -      Obj.template getSectionContentsAsArray<uint32_X>(&Sec);
> -  fatal(EntriesOrErr);
> -  ArrayRef<uint32_X> Entries = *EntriesOrErr;
> +  ArrayRef<uint32_X> Entries =
> +      fatal(Obj.template getSectionContentsAsArray<uint32_X>(&Sec));
>    if (Entries.empty() || Entries[0] != GRP_COMDAT)
>      fatal("Unsupported SHT_GROUP format");
>    return Entries.slice(1);
> @@ -202,12 +193,9 @@ void elf::ObjectFile<ELFT>::initializeSe
>      case SHT_SYMTAB:
>        this->Symtab = &Sec;
>        break;
> -    case SHT_SYMTAB_SHNDX: {
> -      ErrorOr<ArrayRef<Elf_Word>> ErrorOrTable = Obj.getSHNDXTable(Sec);
> -      fatal(ErrorOrTable);
> -      this->SymtabSHNDX = *ErrorOrTable;
> +    case SHT_SYMTAB_SHNDX:
> +      this->SymtabSHNDX = fatal(Obj.getSHNDXTable(Sec));
>        break;
> -    }
>      case SHT_STRTAB:
>      case SHT_NULL:
>        break;
> @@ -248,9 +236,7 @@ void elf::ObjectFile<ELFT>::initializeSe
>  template <class ELFT>
>  InputSectionBase<ELFT> *
>  elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec) {
> -  ErrorOr<StringRef> NameOrErr = this->ELFObj.getSectionName(&Sec);
> -  fatal(NameOrErr);
> -  StringRef Name = *NameOrErr;
> +  StringRef Name = fatal(this->ELFObj.getSectionName(&Sec));
>
>    // .note.GNU-stack is a marker section to control the presence of
>    // PT_GNU_STACK segment in outputs. Since the presence of the segment
> @@ -300,9 +286,7 @@ elf::ObjectFile<ELFT>::getSection(const
>
>  template <class ELFT>
>  SymbolBody *elf::ObjectFile<ELFT>::createSymbolBody(const Elf_Sym *Sym) {
> -  ErrorOr<StringRef> NameOrErr = Sym->getName(this->StringTable);
> -  fatal(NameOrErr);
> -  StringRef Name = *NameOrErr;
> +  StringRef Name = fatal(Sym->getName(this->StringTable));
>
>    switch (Sym->st_shndx) {
>    case SHN_UNDEF:
> @@ -328,9 +312,7 @@ SymbolBody *elf::ObjectFile<ELFT>::creat
>  }
>
>  void ArchiveFile::parse() {
> -  ErrorOr<std::unique_ptr<Archive>> FileOrErr = Archive::create(MB);
> -  fatal(FileOrErr, "Failed to parse archive");
> -  File = std::move(*FileOrErr);
> +  File = fatal(Archive::create(MB), "Failed to parse archive");
>
>    // Allocate a buffer for Lazy objects.
>    size_t NumSyms = File->getNumberOfSymbols();
> @@ -343,18 +325,16 @@ void ArchiveFile::parse() {
>
>  // Returns a buffer pointing to a member file containing a given symbol.
>  MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
> -  ErrorOr<Archive::Child> COrErr = Sym->getMember();
> -  fatal(COrErr, "Could not get the member for symbol " + Sym->getName());
> -  const Archive::Child &C = *COrErr;
> +  Archive::Child C =
> +      fatal(Sym->getMember(),
> +            "Could not get the member for symbol " + Sym->getName());
>
>    if (!Seen.insert(C.getChildOffset()).second)
>      return MemoryBufferRef();
>
> -  ErrorOr<MemoryBufferRef> RefOrErr = C.getMemoryBufferRef();
> -  if (!RefOrErr)
> -    fatal(RefOrErr, "Could not get the buffer for the member defining
> symbol " +
> -                        Sym->getName());
> -  return *RefOrErr;
> +  return fatal(C.getMemoryBufferRef(),
> +               "Could not get the buffer for the member defining symbol "
> +
> +                   Sym->getName());
>  }
>
>  template <class ELFT>
> @@ -367,9 +347,7 @@ SharedFile<ELFT>::getSection(const Elf_S
>    uint32_t Index = this->getSectionIndex(Sym);
>    if (Index == 0)
>      return nullptr;
> -  ErrorOr<const Elf_Shdr *> Ret = this->ELFObj.getSection(Index);
> -  fatal(Ret);
> -  return *Ret;
> +  return fatal(this->ELFObj.getSection(Index));
>  }
>
>  // Partially parse the shared object file so that we can call
> @@ -390,13 +368,10 @@ template <class ELFT> void SharedFile<EL
>      case SHT_DYNAMIC:
>        DynamicSec = &Sec;
>        break;
> -    case SHT_SYMTAB_SHNDX: {
> -      ErrorOr<ArrayRef<Elf_Word>> ErrorOrTable = Obj.getSHNDXTable(Sec);
> -      fatal(ErrorOrTable);
> -      this->SymtabSHNDX = *ErrorOrTable;
> +    case SHT_SYMTAB_SHNDX:
> +      this->SymtabSHNDX = fatal(Obj.getSHNDXTable(Sec));
>        break;
>      }
> -    }
>    }
>
>    this->initStringTable();
> @@ -444,11 +419,8 @@ bool BitcodeFile::classof(const InputFil
>
>  void BitcodeFile::parse(DenseSet<StringRef> &ComdatGroups) {
>    LLVMContext Context;
> -  ErrorOr<std::unique_ptr<IRObjectFile>> ObjOrErr =
> -      IRObjectFile::create(MB, Context);
> -  fatal(ObjOrErr);
> -  IRObjectFile &Obj = **ObjOrErr;
> -  const Module &M = Obj.getModule();
> +  std::unique_ptr<IRObjectFile> Obj = fatal(IRObjectFile::create(MB,
> Context));
> +  const Module &M = Obj->getModule();
>
>    DenseSet<const Comdat *> KeptComdats;
>    for (const auto &P : M.getComdatSymbolTable()) {
> @@ -457,8 +429,8 @@ void BitcodeFile::parse(DenseSet<StringR
>        KeptComdats.insert(&P.second);
>    }
>
> -  for (const BasicSymbolRef &Sym : Obj.symbols()) {
> -    if (const GlobalValue *GV = Obj.getSymbolGV(Sym.getRawDataRefImpl()))
> +  for (const BasicSymbolRef &Sym : Obj->symbols()) {
> +    if (const GlobalValue *GV = Obj->getSymbolGV(Sym.getRawDataRefImpl()))
>        if (const Comdat *C = GV->getComdat())
>          if (!KeptComdats.count(C))
>            continue;
>
> Modified: lld/trunk/ELF/InputSection.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=262626&r1=262625&r2=262626&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/InputSection.cpp (original)
> +++ lld/trunk/ELF/InputSection.cpp Thu Mar  3 10:21:44 2016
> @@ -39,17 +39,12 @@ InputSectionBase<ELFT>::InputSectionBase
>  }
>
>  template <class ELFT> StringRef InputSectionBase<ELFT>::getSectionName()
> const {
> -  ErrorOr<StringRef> Name = File->getObj().getSectionName(this->Header);
> -  fatal(Name);
> -  return *Name;
> +  return fatal(File->getObj().getSectionName(this->Header));
>  }
>
>  template <class ELFT>
>  ArrayRef<uint8_t> InputSectionBase<ELFT>::getSectionData() const {
> -  ErrorOr<ArrayRef<uint8_t>> Ret =
> -      this->File->getObj().getSectionContents(this->Header);
> -  fatal(Ret);
> -  return *Ret;
> +  return fatal(this->File->getObj().getSectionContents(this->Header));
>  }
>
>  template <class ELFT>
>
> Modified: lld/trunk/ELF/SymbolTable.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SymbolTable.cpp?rev=262626&r1=262625&r2=262626&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/SymbolTable.cpp (original)
> +++ lld/trunk/ELF/SymbolTable.cpp Thu Mar  3 10:21:44 2016
> @@ -136,11 +136,9 @@ ObjectFile<ELFT> *SymbolTable<ELFT>::cre
>    for (const std::unique_ptr<BitcodeFile> &F : BitcodeFiles) {
>      std::unique_ptr<MemoryBuffer> Buffer =
>          MemoryBuffer::getMemBuffer(F->MB, false);
> -    ErrorOr<std::unique_ptr<Module>> MOrErr =
> -        getLazyBitcodeModule(std::move(Buffer), Context,
> -                             /*ShouldLazyLoadMetadata*/ true);
> -    fatal(MOrErr);
> -    std::unique_ptr<Module> &M = *MOrErr;
> +    std::unique_ptr<Module> M =
> +        fatal(getLazyBitcodeModule(std::move(Buffer), Context,
> +                                   /*ShouldLazyLoadMetadata*/ true));
>      L.linkInModule(std::move(M));
>    }
>    std::unique_ptr<InputFile> F = codegen(Combined);
>
> Modified: lld/trunk/ELF/Writer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=262626&r1=262625&r2=262626&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Writer.cpp (original)
> +++ lld/trunk/ELF/Writer.cpp Thu Mar  3 10:21:44 2016
> @@ -564,9 +564,7 @@ template <class ELFT> void Writer<ELFT>:
>      return;
>    for (const std::unique_ptr<ObjectFile<ELFT>> &F :
> Symtab.getObjectFiles()) {
>      for (const Elf_Sym &Sym : F->getLocalSymbols()) {
> -      ErrorOr<StringRef> SymNameOrErr = Sym.getName(F->getStringTable());
> -      fatal(SymNameOrErr);
> -      StringRef SymName = *SymNameOrErr;
> +      StringRef SymName = fatal(Sym.getName(F->getStringTable()));
>        if (!shouldKeepInSymtab<ELFT>(*F, SymName, Sym))
>          continue;
>        if (Sym.st_shndx != SHN_ABS) {
>
>
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