[llvm-objcopy][NFC] Propagate errors in removeSymbols/removeSectionReferences

[jhenderson]

LGTM.

llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp

188–189

Is moving this out-of-line just a readability thing (it's fine if so)? Otherwise I'm missing why you're doing it (ditto below).

[rupprecht]

llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp

188–189

Yes, just seemed more readable this way.

llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp

if (EC)
                                Path.data());
   }
   return Error::success();
 }
 
 static Error splitDWOToFile(const CopyConfig &Config, const Reader &Reader,
                             StringRef File, ElfType OutputElfType) {
   auto DWOFile = Reader.create();
-  DWOFile->removeSections(
-      [&](const SectionBase &Sec) { return onlyKeepDWOPred(*DWOFile, Sec); });
+  auto OnlyKeepDWOPred = [&DWOFile](const SectionBase &Sec) {
+    return onlyKeepDWOPred(*DWOFile, Sec);
+  };
+  if (Error E = DWOFile->removeSections(OnlyKeepDWOPred))
+    return E;
   if (Config.OutputArch)
     DWOFile->Machine = Config.OutputArch.getValue().EMachine;
   FileBuffer FB(File);
   auto Writer = createWriter(Config, *DWOFile, FB, OutputElfType);
   if (Error E = Writer->finalize())
     return E;
   return Writer->write();
 }
if (Obj.SymbolTable) {
     // The purpose of this loop is to mark symbols referenced by sections
     // (like GroupSection or RelocationSection). This way, we know which
     // symbols are still 'needed' and which are not.
     if (Config.StripUnneeded) {
       for (auto &Section : Obj.sections())
         Section.markSymbols();
     }
 
-    Obj.removeSymbols([&](const Symbol &Sym) {
+    auto RemoveSymbolsPred = [&](const Symbol &Sym) {
       if (is_contained(Config.SymbolsToKeep, Sym.Name) ||
           (Config.KeepFileSymbols && Sym.Type == STT_FILE))
         return false;
 
       if ((Config.DiscardMode == DiscardType::All ||
            (Config.DiscardMode == DiscardType::Locals &&
             StringRef(Sym.Name).startswith(".L"))) &&
           Sym.Binding == STB_LOCAL && Sym.getShndx() != SHN_UNDEF &&
           Sym.Type != STT_FILE && Sym.Type != STT_SECTION)
         return true;
 
       if (Config.StripAll || Config.StripAllGNU)
         return true;
 
       if (is_contained(Config.SymbolsToRemove, Sym.Name))
         return true;
 
       if (Config.StripUnneeded && !Sym.Referenced &&
           (Sym.Binding == STB_LOCAL || Sym.getShndx() == SHN_UNDEF) &&
           Sym.Type != STT_FILE && Sym.Type != STT_SECTION)
         return true;
 
       return false;
-    });
+    };
+    if (Error E = Obj.removeSymbols(RemoveSymbolsPred))
+      return E;
   }
 
   SectionPred RemovePred = [](const SectionBase &) { return false; };
 
   // Removes:
   if (!Config.ToRemove.empty()) {
     RemovePred = [&Config](const SectionBase &Sec) {
       return is_contained(Config.ToRemove, Sec.Name);
else if (Config.DecompressDebugSections)
     replaceDebugSections(
         Config, Obj, RemovePred,
         [](const SectionBase &S) { return isa<CompressedSection>(&S); },
         [&Obj](const SectionBase *S) {
           auto CS = cast<CompressedSection>(S);
           return &Obj.addSection<DecompressedSection>(*CS);
         });
 
-  Obj.removeSections(RemovePred);
+  if (Error E = Obj.removeSections(RemovePred))
+    return E;
 
   if (!Config.SectionsToRename.empty()) {
     for (auto &Sec : Obj.sections()) {
       const auto Iter = Config.SectionsToRename.find(Sec.Name);
       if (Iter != Config.SectionsToRename.end()) {
         const SectionRename &SR = Iter->second;
         Sec.Name = SR.NewName;
         if (SR.NewFlags.hasValue())

llvm/tools/llvm-objcopy/ELF/Object.h

public:
 
   SectionBase() = default;
   SectionBase(const SectionBase &) = default;
 
   virtual ~SectionBase() = default;
 
   virtual void initialize(SectionTableRef SecTable);
   virtual void finalize();
-  virtual void removeSectionReferences(const SectionBase *Sec);
-  virtual void removeSymbols(function_ref<bool(const Symbol &)> ToRemove);
+  virtual Error removeSectionReferences(const SectionBase *Sec);
+  virtual Error removeSymbols(function_ref<bool(const Symbol &)> ToRemove);
   virtual void accept(SectionVisitor &Visitor) const = 0;
   virtual void accept(MutableSectionVisitor &Visitor) = 0;
   virtual void markSymbols();
 };
 
 class Segment {
 private:
   struct SectionCompare {
class Section : public SectionBase {
   ArrayRef<uint8_t> Contents;
   SectionBase *LinkSection = nullptr;
 
 public:
   explicit Section(ArrayRef<uint8_t> Data) : Contents(Data) {}
 
   void accept(SectionVisitor &Visitor) const override;
   void accept(MutableSectionVisitor &Visitor) override;
-  void removeSectionReferences(const SectionBase *Sec) override;
+  Error removeSectionReferences(const SectionBase *Sec) override;
   void initialize(SectionTableRef SecTable) override;
   void finalize() override;
 };
 
 class OwnedDataSection : public SectionBase {
   MAKE_SEC_WRITER_FRIEND
 
   std::vector<uint8_t> Data;
void setShndxTable(SectionIndexSection *ShndxTable) {
     SectionIndexTable = ShndxTable;
   }
   const SectionIndexSection *getShndxTable() const { return SectionIndexTable; }
   const SectionBase *getStrTab() const { return SymbolNames; }
   const Symbol *getSymbolByIndex(uint32_t Index) const;
   Symbol *getSymbolByIndex(uint32_t Index);
   void updateSymbols(function_ref<void(Symbol &)> Callable);
 
-  void removeSectionReferences(const SectionBase *Sec) override;
+  Error removeSectionReferences(const SectionBase *Sec) override;
   void initialize(SectionTableRef SecTable) override;
   void finalize() override;
   void accept(SectionVisitor &Visitor) const override;
   void accept(MutableSectionVisitor &Visitor) override;
-  void removeSymbols(function_ref<bool(const Symbol &)> ToRemove) override;
+  Error removeSymbols(function_ref<bool(const Symbol &)> ToRemove) override;
 
   static bool classof(const SectionBase *S) {
     return S->Type == ELF::SHT_SYMTAB;
   }
 };
 
 struct Relocation {
   Symbol *RelocSymbol = nullptr;

 class RelocSectionWithSymtabBase : public RelocationSectionBase {
   SymTabType *Symbols = nullptr;
   void setSymTab(SymTabType *SymTab) { Symbols = SymTab; }
 
 protected:
   RelocSectionWithSymtabBase() = default;
 
 public:
-  void removeSectionReferences(const SectionBase *Sec) override;
+  Error removeSectionReferences(const SectionBase *Sec) override;
   void initialize(SectionTableRef SecTable) override;
   void finalize() override;
 };
 
 class RelocationSection
     : public RelocSectionWithSymtabBase<SymbolTableSection> {
   MAKE_SEC_WRITER_FRIEND
 
   std::vector<Relocation> Relocations;
 
 public:
   void addRelocation(Relocation Rel) { Relocations.push_back(Rel); }
   void accept(SectionVisitor &Visitor) const override;
   void accept(MutableSectionVisitor &Visitor) override;
-  void removeSymbols(function_ref<bool(const Symbol &)> ToRemove) override;
+  Error removeSymbols(function_ref<bool(const Symbol &)> ToRemove) override;
   void markSymbols() override;
 
   static bool classof(const SectionBase *S) {
     if (S->Flags & ELF::SHF_ALLOC)
       return false;
     return S->Type == ELF::SHT_REL || S->Type == ELF::SHT_RELA;
   }
 };
public:
   void setSymTab(const SymbolTableSection *SymTabSec) { SymTab = SymTabSec; }
   void setSymbol(Symbol *S) { Sym = S; }
   void setFlagWord(ELF::Elf32_Word W) { FlagWord = W; }
   void addMember(SectionBase *Sec) { GroupMembers.push_back(Sec); }
 
   void accept(SectionVisitor &) const override;
   void accept(MutableSectionVisitor &Visitor) override;
   void finalize() override;
-  void removeSymbols(function_ref<bool(const Symbol &)> ToRemove) override;
+  Error removeSymbols(function_ref<bool(const Symbol &)> ToRemove) override;
   void markSymbols() override;
 
   static bool classof(const SectionBase *S) {
     return S->Type == ELF::SHT_GROUP;
   }
 };
 
 class DynamicSymbolTableSection : public Section {
public:
   void sortSections();
   SectionTableRef sections() { return SectionTableRef(Sections); }
   ConstRange<SectionBase> sections() const {
     return make_pointee_range(Sections);
   }
   Range<Segment> segments() { return make_pointee_range(Segments); }
   ConstRange<Segment> segments() const { return make_pointee_range(Segments); }
 
-  void removeSections(std::function<bool(const SectionBase &)> ToRemove);
-  void removeSymbols(function_ref<bool(const Symbol &)> ToRemove);
+  Error removeSections(std::function<bool(const SectionBase &)> ToRemove);
+  Error removeSymbols(function_ref<bool(const Symbol &)> ToRemove);
   template <class T, class... Ts> T &addSection(Ts &&... Args) {
     auto Sec = llvm::make_unique<T>(std::forward<Ts>(Args)...);
     auto Ptr = Sec.get();
     Sections.emplace_back(std::move(Sec));
     Ptr->Index = Sections.size();
     return *Ptr;
   }
   Segment &addSegment(ArrayRef<uint8_t> Data) {

llvm/tools/llvm-objcopy/ELF/Object.cpp

 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/MC/MCTargetOptions.h"
 #include "llvm/Object/ELFObjectFile.h"
 #include "llvm/Support/Compression.h"
+#include "llvm/Support/Errc.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileOutputBuffer.h"
 #include "llvm/Support/Path.h"
 #include <algorithm>
 #include <cstddef>
 #include <cstdint>
 #include <iterator>
 #include <utility>
template <class ELFT> void ELFWriter<ELFT>::writePhdr(const Segment &Seg) {
   Phdr.p_offset = Seg.Offset;
   Phdr.p_vaddr = Seg.VAddr;
   Phdr.p_paddr = Seg.PAddr;
   Phdr.p_filesz = Seg.FileSize;
   Phdr.p_memsz = Seg.MemSize;
   Phdr.p_align = Seg.Align;
 }
 
-void SectionBase::removeSectionReferences(const SectionBase *Sec) {}
-void SectionBase::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {}
+Error SectionBase::removeSectionReferences(const SectionBase *Sec) {
+  return Error::success();
+}
+
+Error SectionBase::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
+  return Error::success();
+}
+
 void SectionBase::initialize(SectionTableRef SecTable) {}
 void SectionBase::finalize() {}
 void SectionBase::markSymbols() {}
 
 template <class ELFT> void ELFWriter<ELFT>::writeShdr(const SectionBase &Sec) {
   uint8_t *B = Buf.getBufferStart();
   B += Sec.HeaderOffset;
   Elf_Shdr &Shdr = *reinterpret_cast<Elf_Shdr *>(B);
void SymbolTableSection::addSymbol(Twine Name, uint8_t Bind, uint8_t Type,
   Sym.Value = Value;
   Sym.Visibility = Visibility;
   Sym.Size = Size;
   Sym.Index = Symbols.size();
   Symbols.emplace_back(llvm::make_unique<Symbol>(Sym));
   Size += this->EntrySize;
 }
 
-void SymbolTableSection::removeSectionReferences(const SectionBase *Sec) {
+Error SymbolTableSection::removeSectionReferences(const SectionBase *Sec) {
   if (SectionIndexTable == Sec)
     SectionIndexTable = nullptr;
   if (SymbolNames == Sec) {
-    error("String table " + SymbolNames->Name +
-          " cannot be removed because it is referenced by the symbol table " +
-          this->Name);
+    return createStringError(llvm::errc::invalid_argument,
+                             "String table %s cannot be removed because it is "
+                             "referenced by the symbol table %s",
+                             SymbolNames->Name.data(), this->Name.data());
   }
-  removeSymbols([Sec](const Symbol &Sym) { return Sym.DefinedIn == Sec; });
+  return removeSymbols(
+      [Sec](const Symbol &Sym) { return Sym.DefinedIn == Sec; });
 }
 
 void SymbolTableSection::updateSymbols(function_ref<void(Symbol &)> Callable) {
   std::for_each(std::begin(Symbols) + 1, std::end(Symbols),
                 [Callable](SymPtr &Sym) { Callable(*Sym); });
   std::stable_partition(
       std::begin(Symbols), std::end(Symbols),
       [](const SymPtr &Sym) { return Sym->Binding == STB_LOCAL; });
   assignIndices();
 }
 
-void SymbolTableSection::removeSymbols(
+Error SymbolTableSection::removeSymbols(
     function_ref<bool(const Symbol &)> ToRemove) {
   Symbols.erase(
       std::remove_if(std::begin(Symbols) + 1, std::end(Symbols),
                      [ToRemove](const SymPtr &Sym) { return ToRemove(*Sym); }),
       std::end(Symbols));
   Size = Symbols.size() * EntrySize;
   assignIndices();
+  return Error::success();
 }
 
 void SymbolTableSection::initialize(SectionTableRef SecTable) {
   Size = 0;
   setStrTab(SecTable.getSectionOfType<StringTableSection>(
       Link,
       "Symbol table has link index of " + Twine(Link) +
           " which is not a valid index",
void SymbolTableSection::accept(SectionVisitor &Visitor) const {
   Visitor.visit(*this);
 }
 
 void SymbolTableSection::accept(MutableSectionVisitor &Visitor) {
   Visitor.visit(*this);
 }
 
 template <class SymTabType>
-void RelocSectionWithSymtabBase<SymTabType>::removeSectionReferences(
+Error RelocSectionWithSymtabBase<SymTabType>::removeSectionReferences(
     const SectionBase *Sec) {
-  if (Symbols == Sec) {
-    error("Symbol table " + Symbols->Name +
-          " cannot be removed because it is "
-          "referenced by the relocation "
-          "section " +
-          this->Name);
-  }
+  if (Symbols == Sec)
+    return createStringError(llvm::errc::invalid_argument,
+                             "Symbol table %s cannot be removed because it is "
+                             "referenced by the relocation section %s.",
+                             Symbols->Name.data(), this->Name.data());
+  return Error::success();
 }
 
 template <class SymTabType>
 void RelocSectionWithSymtabBase<SymTabType>::initialize(
     SectionTableRef SecTable) {
   if (Link != SHN_UNDEF)
     setSymTab(SecTable.getSectionOfType<SymTabType>(
         Link,

 void RelocationSection::accept(SectionVisitor &Visitor) const {
   Visitor.visit(*this);
 }
 
 void RelocationSection::accept(MutableSectionVisitor &Visitor) {
   Visitor.visit(*this);
 }
 
-void RelocationSection::removeSymbols(
+Error RelocationSection::removeSymbols(
     function_ref<bool(const Symbol &)> ToRemove) {
   for (const Relocation &Reloc : Relocations)
     if (ToRemove(*Reloc.RelocSymbol))
-      error("not stripping symbol '" + Reloc.RelocSymbol->Name +
-            "' because it is named in a relocation");
+      return createStringError(
+          llvm::errc::invalid_argument,
+          "not stripping symbol '%s' because it is named in a relocation.",
+          Reloc.RelocSymbol->Name.data());
+  return Error::success();
 }
 
 void RelocationSection::markSymbols() {
   for (const Relocation &Reloc : Relocations)
     Reloc.RelocSymbol->Referenced = true;
 }
 
 void SectionWriter::visit(const DynamicRelocationSection &Sec) {
   llvm::copy(Sec.Contents,
             Out.getBufferStart() + Sec.Offset);
 }
 
 void DynamicRelocationSection::accept(SectionVisitor &Visitor) const {
   Visitor.visit(*this);
 }
 
 void DynamicRelocationSection::accept(MutableSectionVisitor &Visitor) {
   Visitor.visit(*this);
 }
 
-void Section::removeSectionReferences(const SectionBase *Sec) {
-  if (LinkSection == Sec) {
-    error("Section " + LinkSection->Name +
-          " cannot be removed because it is "
-          "referenced by the section " +
-          this->Name);
-  }
+Error Section::removeSectionReferences(const SectionBase *Sec) {
+  if (LinkSection == Sec)
+    return createStringError(llvm::errc::invalid_argument,
+                             "Section %s cannot be removed because it is "
+                             "referenced by the section %s",
+                             LinkSection->Name.data(), this->Name.data());
+  return Error::success();
 }
 
 void GroupSection::finalize() {
   this->Info = Sym->Index;
   this->Link = SymTab->Index;
 }
 
-void GroupSection::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
-  if (ToRemove(*Sym)) {
-    error("Symbol " + Sym->Name +
-          " cannot be removed because it is "
-          "referenced by the section " +
-          this->Name + "[" + Twine(this->Index) + "]");
-  }
+Error GroupSection::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
+  if (ToRemove(*Sym))
+    return createStringError(llvm::errc::invalid_argument,
+                             "Symbol %s cannot be removed because it is "
+                             "referenced by the section %s[%d].",
+                             Sym->Name.data(), this->Name.data(), this->Index);
+  return Error::success();
 }
 
 void GroupSection::markSymbols() {
   if (Sym)
     Sym->Referenced = true;
 }
 
 void Section::initialize(SectionTableRef SecTable) {
for (auto &Sec : Obj.sections())
     writeShdr(Sec);
 }
 
 template <class ELFT> void ELFWriter<ELFT>::writeSectionData() {
   for (auto &Sec : Obj.sections())
     Sec.accept(*SecWriter);
 }
 
-void Object::removeSections(std::function<bool(const SectionBase &)> ToRemove) {
+Error Object::removeSections(
+    std::function<bool(const SectionBase &)> ToRemove) {
 
   auto Iter = std::stable_partition(
       std::begin(Sections), std::end(Sections), [=](const SecPtr &Sec) {
         if (ToRemove(*Sec))
           return false;
         if (auto RelSec = dyn_cast<RelocationSectionBase>(Sec.get())) {
           if (auto ToRelSec = RelSec->getSection())
             return !ToRemove(*ToRelSec);
         }
         return true;
       });
   if (SymbolTable != nullptr && ToRemove(*SymbolTable))
     SymbolTable = nullptr;
   if (SectionNames != nullptr && ToRemove(*SectionNames))
     SectionNames = nullptr;
   if (SectionIndexTable != nullptr && ToRemove(*SectionIndexTable))
     SectionIndexTable = nullptr;
   // Now make sure there are no remaining references to the sections that will
   // be removed. Sometimes it is impossible to remove a reference so we emit
   // an error here instead.
   for (auto &RemoveSec : make_range(Iter, std::end(Sections))) {
     for (auto &Segment : Segments)
       Segment->removeSection(RemoveSec.get());
     for (auto &KeepSec : make_range(std::begin(Sections), Iter))
-      KeepSec->removeSectionReferences(RemoveSec.get());
+      if (Error E = KeepSec->removeSectionReferences(RemoveSec.get()))
+        return E;
   }
   // Now finally get rid of them all togethor.
   Sections.erase(Iter, std::end(Sections));
+  return Error::success();
 }
 
-void Object::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
-  if (!SymbolTable)
-    return;
-
+Error Object::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
+  if (SymbolTable)
     for (const SecPtr &Sec : Sections)
-    Sec->removeSymbols(ToRemove);
+      if (Error E = Sec->removeSymbols(ToRemove))
+        return E;
+  return Error::success();
 }
 
 void Object::sortSections() {
   // Put all sections in offset order. Maintain the ordering as closely as
   // possible while meeting that demand however.
   auto CompareSections = [](const SecPtr &A, const SecPtr &B) {
     return A->OriginalOffset < B->OriginalOffset;
   };
template <class ELFT> Error ELFWriter<ELFT>::write() {
   return Buf.commit();
 }
 
 template <class ELFT> Error ELFWriter<ELFT>::finalize() {
   // It could happen that SectionNames has been removed and yet the user wants
   // a section header table output. We need to throw an error if a user tries
   // to do that.
   if (Obj.SectionNames == nullptr && WriteSectionHeaders)
-    error("Cannot write section header table because section header string "
-          "table was removed.");
+    return createStringError(llvm::errc::invalid_argument,
+                             "Cannot write section header table because "
+                             "section header string table was removed.");
 
   Obj.sortSections();
 
   // We need to assign indexes before we perform layout because we need to know
   // if we need large indexes or not. We can assign indexes first and check as
   // we go to see if we will actully need large indexes.
   bool NeedsLargeIndexes = false;
   if (size(Obj.sections()) >= SHN_LORESERVE) {
if (Obj.SymbolTable != nullptr && Obj.SectionIndexTable == nullptr) {
       auto &Shndx = Obj.addSection<SectionIndexSection>();
       Obj.SymbolTable->setShndxTable(&Shndx);
       Shndx.setSymTab(Obj.SymbolTable);
     }
   } else {
     // Since we don't need SectionIndexTable we should remove it and all
     // references to it.
     if (Obj.SectionIndexTable != nullptr) {
-      Obj.removeSections([this](const SectionBase &Sec) {
+      if (Error E = Obj.removeSections([this](const SectionBase &Sec) {
             return &Sec == Obj.SectionIndexTable;
-      });
+          }))
+        return E;
     }
   }
 
   // Make sure we add the names of all the sections. Importantly this must be
   // done after we decide to add or remove SectionIndexes.
   if (Obj.SectionNames != nullptr)
     for (const auto &Section : Obj.sections()) {
       Obj.SectionNames->addString(Section.Name);