[yaml2obj/ObjectYAML] - Cleanup the error reporting API, add custom errors handlers.

This is a continuation of the YAML library error reporting
refactoring/improvement and the idea by itself was mentioned
in the following thread:
https://reviews.llvm.org/D67182?id=218714#inline-603404

This performs a cleanup of all object emitters in the library.
It allows using the custom one provided by the caller.

One of the nice things is that each tool can now print its tool name,
e.g: "yaml2obj: error: <text>"

Also, the code became a bit simpler.

Differential revision: https://reviews.llvm.org/D67445

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371865 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ObjectYAML/yaml2obj.h

@@ -44,17 +44,22 @@ namespace yaml {
 class Input;
 struct YamlObjectFile;
 
-bool yaml2coff(COFFYAML::Object &Doc, raw_ostream &Out);
-bool yaml2elf(ELFYAML::Object &Doc, raw_ostream &Out);
-bool yaml2macho(YamlObjectFile &Doc, raw_ostream &Out);
-bool yaml2minidump(MinidumpYAML::Object &Doc, raw_ostream &Out);
-bool yaml2wasm(WasmYAML::Object &Doc, raw_ostream &Out);
+using ErrorHandler = llvm::function_ref<void(const Twine &Msg)>;
 
-Error convertYAML(Input &YIn, raw_ostream &Out, unsigned DocNum = 1);
+bool yaml2coff(COFFYAML::Object &Doc, raw_ostream &Out, ErrorHandler EH);
+bool yaml2elf(ELFYAML::Object &Doc, raw_ostream &Out, ErrorHandler EH);
+bool yaml2macho(YamlObjectFile &Doc, raw_ostream &Out, ErrorHandler EH);
+bool yaml2minidump(MinidumpYAML::Object &Doc, raw_ostream &Out,
+                   ErrorHandler EH);
+bool yaml2wasm(WasmYAML::Object &Doc, raw_ostream &Out, ErrorHandler EH);
+
+bool convertYAML(Input &YIn, raw_ostream &Out, ErrorHandler ErrHandler,
+                 unsigned DocNum = 1);
 
 /// Convenience function for tests.
-Expected<std::unique_ptr<object::ObjectFile>>
-yaml2ObjectFile(SmallVectorImpl<char> &Storage, StringRef Yaml);
+std::unique_ptr<object::ObjectFile>
+yaml2ObjectFile(SmallVectorImpl<char> &Storage, StringRef Yaml,
+                ErrorHandler ErrHandler);
 
 } // namespace yaml
 } // namespace llvm

lib/ObjectYAML/COFFEmitter.cpp

@@ -34,8 +34,8 @@ namespace {
 /// This parses a yaml stream that represents a COFF object file.
 /// See docs/yaml2obj for the yaml scheema.
 struct COFFParser {
-  COFFParser(COFFYAML::Object &Obj)
-      : Obj(Obj), SectionTableStart(0), SectionTableSize(0) {
+  COFFParser(COFFYAML::Object &Obj, yaml::ErrorHandler EH)
+      : Obj(Obj), SectionTableStart(0), SectionTableSize(0), ErrHandler(EH) {
     // A COFF string table always starts with a 4 byte size field. Offsets into
     // it include this size, so allocate it now.
     StringTable.append(4, char(0));
@@ -81,7 +81,7 @@ struct COFFParser {
         unsigned Index = getStringIndex(Name);
         std::string str = utostr(Index);
         if (str.size() > 7) {
-          errs() << "String table got too large\n";
+          ErrHandler("string table got too large");
           return false;
         }
         Sec.Header.Name[0] = '/';
@@ -90,11 +90,11 @@ struct COFFParser {
 
       if (Sec.Alignment) {
         if (Sec.Alignment > 8192) {
-          errs() << "Section alignment is too large\n";
+          ErrHandler("section alignment is too large");
           return false;
         }
         if (!isPowerOf2_32(Sec.Alignment)) {
-          errs() << "Section alignment is not a power of 2\n";
+          ErrHandler("section alignment is not a power of 2");
           return false;
         }
         Sec.Header.Characteristics |= (Log2_32(Sec.Alignment) + 1) << 20;
@@ -155,6 +155,8 @@ struct COFFParser {
   std::string StringTable;
   uint32_t SectionTableStart;
   uint32_t SectionTableSize;
+
+  yaml::ErrorHandler ErrHandler;
 };
 
 enum { DOSStubSize = 128 };
@@ -592,24 +594,25 @@ static bool writeCOFF(COFFParser &CP, raw_ostream &OS) {
 namespace llvm {
 namespace yaml {
 
-bool yaml2coff(llvm::COFFYAML::Object &Doc, raw_ostream &Out) {
-  COFFParser CP(Doc);
+bool yaml2coff(llvm::COFFYAML::Object &Doc, raw_ostream &Out,
+               ErrorHandler ErrHandler) {
+  COFFParser CP(Doc, ErrHandler);
   if (!CP.parse()) {
-    errs() << "yaml2obj: Failed to parse YAML file!\n";
+    ErrHandler("failed to parse YAML file");
     return false;
   }
 
   if (!layoutOptionalHeader(CP)) {
-    errs() << "yaml2obj: Failed to layout optional header for COFF file!\n";
+    ErrHandler("failed to layout optional header for COFF file");
     return false;
   }
 
   if (!layoutCOFF(CP)) {
-    errs() << "yaml2obj: Failed to layout COFF file!\n";
+    ErrHandler("failed to layout COFF file");
     return false;
   }
   if (!writeCOFF(CP, Out)) {
-    errs() << "yaml2obj: Failed to write COFF file!\n";
+    ErrHandler("failed to write COFF file");
     return false;
   }
   return true;

lib/ObjectYAML/ELFEmitter.cpp

@@ -115,12 +115,13 @@ template <class ELFT> class ELFState {
   ELFYAML::Object &Doc;
 
   bool HasError = false;
+  yaml::ErrorHandler ErrHandler;
+  void reportError(const Twine &Msg);
 
   std::vector<Elf_Sym> toELFSymbols(ArrayRef<ELFYAML::Symbol> Symbols,
                                     const StringTableBuilder &Strtab);
   unsigned toSectionIndex(StringRef S, StringRef LocSec, StringRef LocSym = "");
   unsigned toSymbolIndex(StringRef S, StringRef LocSec, bool IsDynamic);
-  void reportError(const Twine &Msg);
 
   void buildSectionIndex();
   void buildSymbolIndexes();
@@ -166,9 +167,11 @@ template <class ELFT> class ELFState {
   void writeSectionContent(Elf_Shdr &SHeader,
                            const ELFYAML::DynamicSection &Section,
                            ContiguousBlobAccumulator &CBA);
-  ELFState(ELFYAML::Object &D);
+  ELFState(ELFYAML::Object &D, yaml::ErrorHandler EH);
+
 public:
-  static bool writeELF(raw_ostream &OS, ELFYAML::Object &Doc);
+  static bool writeELF(raw_ostream &OS, ELFYAML::Object &Doc,
+                       yaml::ErrorHandler EH);
 };
 } // end anonymous namespace
 
@@ -182,7 +185,9 @@ template <class T> static void writeArrayData(raw_ostream &OS, ArrayRef<T> A) {
 
 template <class T> static void zero(T &Obj) { memset(&Obj, 0, sizeof(Obj)); }
 
-template <class ELFT> ELFState<ELFT>::ELFState(ELFYAML::Object &D) : Doc(D) {
+template <class ELFT>
+ELFState<ELFT>::ELFState(ELFYAML::Object &D, yaml::ErrorHandler EH)
+    : Doc(D), ErrHandler(EH) {
   StringSet<> DocSections;
   for (std::unique_ptr<ELFYAML::Section> &D : Doc.Sections)
     if (!D->Name.empty())
@@ -592,7 +597,7 @@ void ELFState<ELFT>::initStrtabSectionHeader(Elf_Shdr &SHeader, StringRef Name,
 }
 
 template <class ELFT> void ELFState<ELFT>::reportError(const Twine &Msg) {
-  WithColor::error() << Msg << "\n";
+  ErrHandler(Msg);
   HasError = true;
 }
 
@@ -983,8 +988,9 @@ template <class ELFT> void ELFState<ELFT>::finalizeStrings() {
 }
 
 template <class ELFT>
-bool ELFState<ELFT>::writeELF(raw_ostream &OS, ELFYAML::Object &Doc) {
-  ELFState<ELFT> State(Doc);
+bool ELFState<ELFT>::writeELF(raw_ostream &OS, ELFYAML::Object &Doc,
+                              yaml::ErrorHandler EH) {
+  ELFState<ELFT> State(Doc, EH);
 
   // Finalize .strtab and .dynstr sections. We do that early because want to
   // finalize the string table builders before writing the content of the
@@ -1022,17 +1028,17 @@ bool ELFState<ELFT>::writeELF(raw_ostream &OS, ELFYAML::Object &Doc) {
 namespace llvm {
 namespace yaml {
 
-bool yaml2elf(llvm::ELFYAML::Object &Doc, raw_ostream &Out) {
+bool yaml2elf(llvm::ELFYAML::Object &Doc, raw_ostream &Out, ErrorHandler EH) {
   bool IsLE = Doc.Header.Data == ELFYAML::ELF_ELFDATA(ELF::ELFDATA2LSB);
   bool Is64Bit = Doc.Header.Class == ELFYAML::ELF_ELFCLASS(ELF::ELFCLASS64);
   if (Is64Bit) {
     if (IsLE)
-      return ELFState<object::ELF64LE>::writeELF(Out, Doc);
-    return ELFState<object::ELF64BE>::writeELF(Out, Doc);
+      return ELFState<object::ELF64LE>::writeELF(Out, Doc, EH);
+    return ELFState<object::ELF64BE>::writeELF(Out, Doc, EH);
   }
   if (IsLE)
-    return ELFState<object::ELF32LE>::writeELF(Out, Doc);
-  return ELFState<object::ELF32BE>::writeELF(Out, Doc);
+    return ELFState<object::ELF32LE>::writeELF(Out, Doc, EH);
+  return ELFState<object::ELF32BE>::writeELF(Out, Doc, EH);
 }
 
 } // namespace yaml

lib/ObjectYAML/MachOEmitter.cpp

@@ -15,7 +15,6 @@
 #include "llvm/ObjectYAML/DWARFEmitter.h"
 #include "llvm/ObjectYAML/ObjectYAML.h"
 #include "llvm/ObjectYAML/yaml2obj.h"
-#include "llvm/Support/Error.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Support/YAMLTraits.h"
 #include "llvm/Support/raw_ostream.h"
@@ -34,24 +33,24 @@ public:
     memset(reinterpret_cast<void *>(&Header), 0, sizeof(MachO::mach_header_64));
   }
 
-  Error writeMachO(raw_ostream &OS);
+  void writeMachO(raw_ostream &OS);
 
 private:
-  Error writeHeader(raw_ostream &OS);
-  Error writeLoadCommands(raw_ostream &OS);
-  Error writeSectionData(raw_ostream &OS);
-  Error writeLinkEditData(raw_ostream &OS);
+  void writeHeader(raw_ostream &OS);
+  void writeLoadCommands(raw_ostream &OS);
+  void writeSectionData(raw_ostream &OS);
+  void writeLinkEditData(raw_ostream &OS);
 
   void writeBindOpcodes(raw_ostream &OS,
                         std::vector<MachOYAML::BindOpcode> &BindOpcodes);
   // LinkEdit writers
-  Error writeRebaseOpcodes(raw_ostream &OS);
-  Error writeBasicBindOpcodes(raw_ostream &OS);
-  Error writeWeakBindOpcodes(raw_ostream &OS);
-  Error writeLazyBindOpcodes(raw_ostream &OS);
-  Error writeNameList(raw_ostream &OS);
-  Error writeStringTable(raw_ostream &OS);
-  Error writeExportTrie(raw_ostream &OS);
+  void writeRebaseOpcodes(raw_ostream &OS);
+  void writeBasicBindOpcodes(raw_ostream &OS);
+  void writeWeakBindOpcodes(raw_ostream &OS);
+  void writeLazyBindOpcodes(raw_ostream &OS);
+  void writeNameList(raw_ostream &OS);
+  void writeStringTable(raw_ostream &OS);
+  void writeExportTrie(raw_ostream &OS);
 
   void dumpExportEntry(raw_ostream &OS, MachOYAML::ExportEntry &Entry);
   void ZeroToOffset(raw_ostream &OS, size_t offset);
@@ -63,18 +62,14 @@ private:
   MachO::mach_header_64 Header;
 };
 
-Error MachOWriter::writeMachO(raw_ostream &OS) {
+void MachOWriter::writeMachO(raw_ostream &OS) {
   fileStart = OS.tell();
-  if (auto Err = writeHeader(OS))
-    return Err;
-  if (auto Err = writeLoadCommands(OS))
-    return Err;
-  if (auto Err = writeSectionData(OS))
-    return Err;
-  return Error::success();
+  writeHeader(OS);
+  writeLoadCommands(OS);
+  writeSectionData(OS);
 }
 
-Error MachOWriter::writeHeader(raw_ostream &OS) {
+void MachOWriter::writeHeader(raw_ostream &OS) {
   Header.magic = Obj.Header.magic;
   Header.cputype = Obj.Header.cputype;
   Header.cpusubtype = Obj.Header.cpusubtype;
@@ -90,8 +85,6 @@ Error MachOWriter::writeHeader(raw_ostream &OS) {
   auto header_size =
       is64Bit ? sizeof(MachO::mach_header_64) : sizeof(MachO::mach_header);
   OS.write((const char *)&Header, header_size);
-
-  return Error::success();
 }
 
 template <typename SectionType>
@@ -212,7 +205,7 @@ void MachOWriter::ZeroToOffset(raw_ostream &OS, size_t Offset) {
     ZeroFillBytes(OS, Offset - currOffset);
 }
 
-Error MachOWriter::writeLoadCommands(raw_ostream &OS) {
+void MachOWriter::writeLoadCommands(raw_ostream &OS) {
   for (auto &LC : Obj.LoadCommands) {
     size_t BytesWritten = 0;
     llvm::MachO::macho_load_command Data = LC.Data;
@@ -259,10 +252,9 @@ Error MachOWriter::writeLoadCommands(raw_ostream &OS) {
       ZeroFillBytes(OS, BytesRemaining);
     }
   }
-  return Error::success();
 }
 
-Error MachOWriter::writeSectionData(raw_ostream &OS) {
+void MachOWriter::writeSectionData(raw_ostream &OS) {
   bool FoundLinkEditSeg = false;
   for (auto &LC : Obj.LoadCommands) {
     switch (LC.Data.load_command_data.cmd) {
@@ -273,8 +265,7 @@ Error MachOWriter::writeSectionData(raw_ostream &OS) {
       if (0 ==
           strncmp(&LC.Data.segment_command_data.segname[0], "__LINKEDIT", 16)) {
         FoundLinkEditSeg = true;
-        if (auto Err = writeLinkEditData(OS))
-          return Err;
+        writeLinkEditData(OS);
       }
       for (auto &Sec : LC.Sections) {
         ZeroToOffset(OS, Sec.offset);
@@ -326,11 +317,8 @@ Error MachOWriter::writeSectionData(raw_ostream &OS) {
   }
   // Old PPC Object Files didn't have __LINKEDIT segments, the data was just
   // stuck at the end of the file.
-  if (!FoundLinkEditSeg) {
-    if (auto Err = writeLinkEditData(OS))
-      return Err;
-  }
-  return Error::success();
+  if (!FoundLinkEditSeg)
+    writeLinkEditData(OS);
 }
 
 void MachOWriter::writeBindOpcodes(
@@ -377,9 +365,8 @@ void MachOWriter::dumpExportEntry(raw_ostream &OS,
     dumpExportEntry(OS, EE);
 }
 
-Error MachOWriter::writeExportTrie(raw_ostream &OS) {
+void MachOWriter::writeExportTrie(raw_ostream &OS) {
   dumpExportEntry(OS, Obj.LinkEdit.ExportTrie);
-  return Error::success();
 }
 
 template <typename NListType>
@@ -397,8 +384,8 @@ void writeNListEntry(MachOYAML::NListEntry &NLE, raw_ostream &OS,
   OS.write(reinterpret_cast<const char *>(&ListEntry), sizeof(NListType));
 }
 
-Error MachOWriter::writeLinkEditData(raw_ostream &OS) {
-  typedef Error (MachOWriter::*writeHandler)(raw_ostream &);
+void MachOWriter::writeLinkEditData(raw_ostream &OS) {
+  typedef void (MachOWriter::*writeHandler)(raw_ostream &);
   typedef std::pair<uint64_t, writeHandler> writeOperation;
   std::vector<writeOperation> WriteQueue;
 
@@ -435,57 +422,47 @@ Error MachOWriter::writeLinkEditData(raw_ostream &OS) {
 
   for (auto writeOp : WriteQueue) {
     ZeroToOffset(OS, writeOp.first);
-    if (auto Err = (this->*writeOp.second)(OS))
-      return Err;
+    (this->*writeOp.second)(OS);
   }
-
-  return Error::success();
 }
 
-Error MachOWriter::writeRebaseOpcodes(raw_ostream &OS) {
+void MachOWriter::writeRebaseOpcodes(raw_ostream &OS) {
   MachOYAML::LinkEditData &LinkEdit = Obj.LinkEdit;
 
   for (auto Opcode : LinkEdit.RebaseOpcodes) {
     uint8_t OpByte = Opcode.Opcode | Opcode.Imm;
     OS.write(reinterpret_cast<char *>(&OpByte), 1);
-    for (auto Data : Opcode.ExtraData) {
+    for (auto Data : Opcode.ExtraData)
       encodeULEB128(Data, OS);
-    }
   }
-  return Error::success();
 }
 
-Error MachOWriter::writeBasicBindOpcodes(raw_ostream &OS) {
+void MachOWriter::writeBasicBindOpcodes(raw_ostream &OS) {
   writeBindOpcodes(OS, Obj.LinkEdit.BindOpcodes);
-  return Error::success();
 }
 
-Error MachOWriter::writeWeakBindOpcodes(raw_ostream &OS) {
+void MachOWriter::writeWeakBindOpcodes(raw_ostream &OS) {
   writeBindOpcodes(OS, Obj.LinkEdit.WeakBindOpcodes);
-  return Error::success();
 }
 
-Error MachOWriter::writeLazyBindOpcodes(raw_ostream &OS) {
+void MachOWriter::writeLazyBindOpcodes(raw_ostream &OS) {
   writeBindOpcodes(OS, Obj.LinkEdit.LazyBindOpcodes);
-  return Error::success();
 }
 
-Error MachOWriter::writeNameList(raw_ostream &OS) {
+void MachOWriter::writeNameList(raw_ostream &OS) {
   for (auto NLE : Obj.LinkEdit.NameList) {
     if (is64Bit)
       writeNListEntry<MachO::nlist_64>(NLE, OS, Obj.IsLittleEndian);
     else
       writeNListEntry<MachO::nlist>(NLE, OS, Obj.IsLittleEndian);
   }
-  return Error::success();
 }
 
-Error MachOWriter::writeStringTable(raw_ostream &OS) {
+void MachOWriter::writeStringTable(raw_ostream &OS) {
   for (auto Str : Obj.LinkEdit.StringTable) {
     OS.write(Str.data(), Str.size());
     OS.write('\0');
   }
-  return Error::success();
 }
 
 class UniversalWriter {
@@ -493,11 +470,11 @@ public:
   UniversalWriter(yaml::YamlObjectFile &ObjectFile)
       : ObjectFile(ObjectFile), fileStart(0) {}
 
-  Error writeMachO(raw_ostream &OS);
+  void writeMachO(raw_ostream &OS);
 
 private:
-  Error writeFatHeader(raw_ostream &OS);
-  Error writeFatArchs(raw_ostream &OS);
+  void writeFatHeader(raw_ostream &OS);
+  void writeFatArchs(raw_ostream &OS);
 
   void ZeroToOffset(raw_ostream &OS, size_t offset);
 
@@ -505,30 +482,30 @@ private:
   uint64_t fileStart;
 };
 
-Error UniversalWriter::writeMachO(raw_ostream &OS) {
+void UniversalWriter::writeMachO(raw_ostream &OS) {
   fileStart = OS.tell();
   if (ObjectFile.MachO) {
     MachOWriter Writer(*ObjectFile.MachO);
-    return Writer.writeMachO(OS);
+    Writer.writeMachO(OS);
+    return;
   }
-  if (auto Err = writeFatHeader(OS))
-    return Err;
-  if (auto Err = writeFatArchs(OS))
-    return Err;
+
+  writeFatHeader(OS);
+  writeFatArchs(OS);
+
   auto &FatFile = *ObjectFile.FatMachO;
   assert(FatFile.FatArchs.size() == FatFile.Slices.size());
   for (size_t i = 0; i < FatFile.Slices.size(); i++) {
     ZeroToOffset(OS, FatFile.FatArchs[i].offset);
     MachOWriter Writer(FatFile.Slices[i]);
-    if (auto Err = Writer.writeMachO(OS))
-      return Err;
+    Writer.writeMachO(OS);
+
     auto SliceEnd = FatFile.FatArchs[i].offset + FatFile.FatArchs[i].size;
     ZeroToOffset(OS, SliceEnd);
   }
-  return Error::success();
 }
 
-Error UniversalWriter::writeFatHeader(raw_ostream &OS) {
+void UniversalWriter::writeFatHeader(raw_ostream &OS) {
   auto &FatFile = *ObjectFile.FatMachO;
   MachO::fat_header header;
   header.magic = FatFile.Header.magic;
@@ -536,7 +513,6 @@ Error UniversalWriter::writeFatHeader(raw_ostream &OS) {
   if (sys::IsLittleEndianHost)
     swapStruct(header);
   OS.write(reinterpret_cast<const char *>(&header), sizeof(MachO::fat_header));
-  return Error::success();
 }
 
 template <typename FatArchType>
@@ -572,7 +548,7 @@ void writeFatArch<MachO::fat_arch_64>(MachOYAML::FatArch &Arch,
            sizeof(MachO::fat_arch_64));
 }
 
-Error UniversalWriter::writeFatArchs(raw_ostream &OS) {
+void UniversalWriter::writeFatArchs(raw_ostream &OS) {
   auto &FatFile = *ObjectFile.FatMachO;
   bool is64Bit = FatFile.Header.magic == MachO::FAT_MAGIC_64;
   for (auto Arch : FatFile.FatArchs) {
@@ -581,8 +557,6 @@ Error UniversalWriter::writeFatArchs(raw_ostream &OS) {
     else
       writeFatArch<MachO::fat_arch>(Arch, OS);
   }
-
-  return Error::success();
 }
 
 void UniversalWriter::ZeroToOffset(raw_ostream &OS, size_t Offset) {
@@ -596,12 +570,9 @@ void UniversalWriter::ZeroToOffset(raw_ostream &OS, size_t Offset) {
 namespace llvm {
 namespace yaml {
 
-bool yaml2macho(YamlObjectFile &Doc, raw_ostream &Out) {
+bool yaml2macho(YamlObjectFile &Doc, raw_ostream &Out, ErrorHandler /*EH*/) {
   UniversalWriter Writer(Doc);
-  if (auto Err = Writer.writeMachO(Out)) {
-    errs() << toString(std::move(Err));
-    return false;
-  }
+  Writer.writeMachO(Out);
   return true;
 }
 

lib/ObjectYAML/MinidumpEmitter.cpp

@@ -198,7 +198,8 @@ static Directory layout(BlobAllocator &File, Stream &S) {
 namespace llvm {
 namespace yaml {
 
-bool yaml2minidump(MinidumpYAML::Object &Obj, raw_ostream &Out) {
+bool yaml2minidump(MinidumpYAML::Object &Obj, raw_ostream &Out,
+                   ErrorHandler /*EH*/) {
   BlobAllocator File;
   File.allocateObject(Obj.Header);
 

lib/ObjectYAML/WasmEmitter.cpp

@@ -25,39 +25,46 @@ namespace {
 /// See docs/yaml2obj for the yaml scheema.
 class WasmWriter {
 public:
-  WasmWriter(WasmYAML::Object &Obj) : Obj(Obj) {}
+  WasmWriter(WasmYAML::Object &Obj, yaml::ErrorHandler EH)
+      : Obj(Obj), ErrHandler(EH) {}
   bool writeWasm(raw_ostream &OS);
 
 private:
-  int writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec,
-                        uint32_t SectionIndex);
-
-  int writeSectionContent(raw_ostream &OS, WasmYAML::CustomSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::TypeSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::ImportSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::FunctionSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::TableSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::MemorySection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::GlobalSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::EventSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::ExportSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::StartSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::ElemSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::CodeSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::DataSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::DataCountSection &Section);
+  void writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec,
+                         uint32_t SectionIndex);
+
+  void writeInitExpr(raw_ostream &OS, const wasm::WasmInitExpr &InitExpr);
+
+  void writeSectionContent(raw_ostream &OS, WasmYAML::CustomSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::TypeSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::ImportSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::FunctionSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::TableSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::MemorySection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::GlobalSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::EventSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::ExportSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::StartSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::ElemSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::CodeSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::DataSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::DataCountSection &Section);
 
   // Custom section types
-  int writeSectionContent(raw_ostream &OS, WasmYAML::DylinkSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::NameSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::LinkingSection &Section);
-  int writeSectionContent(raw_ostream &OS, WasmYAML::ProducersSection &Section);
-  int writeSectionContent(raw_ostream &OS,
+  void writeSectionContent(raw_ostream &OS, WasmYAML::DylinkSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::NameSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::LinkingSection &Section);
+  void writeSectionContent(raw_ostream &OS, WasmYAML::ProducersSection &Section);
+  void writeSectionContent(raw_ostream &OS,
                           WasmYAML::TargetFeaturesSection &Section);
   WasmYAML::Object &Obj;
   uint32_t NumImportedFunctions = 0;
   uint32_t NumImportedGlobals = 0;
   uint32_t NumImportedEvents = 0;
+
+  bool HasError = false;
+  yaml::ErrorHandler ErrHandler;
+  void reportError(const Twine &Msg);
 };
 
 class SubSectionWriter {
@@ -115,7 +122,13 @@ static int writeLimits(const WasmYAML::Limits &Lim, raw_ostream &OS) {
   return 0;
 }
 
-static int writeInitExpr(const wasm::WasmInitExpr &InitExpr, raw_ostream &OS) {
+void WasmWriter::reportError(const Twine &Msg) {
+  ErrHandler(Msg);
+  HasError = true;
+}
+
+void WasmWriter::writeInitExpr(raw_ostream &OS,
+                               const wasm::WasmInitExpr &InitExpr) {
   writeUint8(OS, InitExpr.Opcode);
   switch (InitExpr.Opcode) {
   case wasm::WASM_OPCODE_I32_CONST:
@@ -134,29 +147,26 @@ static int writeInitExpr(const wasm::WasmInitExpr &InitExpr, raw_ostream &OS) {
     encodeULEB128(InitExpr.Value.Global, OS);
     break;
   default:
-    errs() << "Unknown opcode in init_expr: " << InitExpr.Opcode << "\n";
-    return 1;
+    reportError("unknown opcode in init_expr: " + Twine(InitExpr.Opcode));
+    return;
   }
   writeUint8(OS, wasm::WASM_OPCODE_END);
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::DylinkSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::DylinkSection &Section) {
   writeStringRef(Section.Name, OS);
   encodeULEB128(Section.MemorySize, OS);
   encodeULEB128(Section.MemoryAlignment, OS);
   encodeULEB128(Section.TableSize, OS);
   encodeULEB128(Section.TableAlignment, OS);
   encodeULEB128(Section.Needed.size(), OS);
-  for (StringRef Needed : Section.Needed) {
+  for (StringRef Needed : Section.Needed)
     writeStringRef(Needed, OS);
-  }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::LinkingSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::LinkingSection &Section) {
   writeStringRef(Section.Name, OS);
   encodeULEB128(Section.Version, OS);
 
@@ -240,12 +250,10 @@ int WasmWriter::writeSectionContent(raw_ostream &OS,
     }
     SubSection.done();
   }
-
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::NameSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::NameSection &Section) {
   writeStringRef(Section.Name, OS);
   if (Section.FunctionNames.size()) {
     writeUint8(OS, wasm::WASM_NAMES_FUNCTION);
@@ -260,16 +268,15 @@ int WasmWriter::writeSectionContent(raw_ostream &OS,
 
     SubSection.done();
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::ProducersSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::ProducersSection &Section) {
   writeStringRef(Section.Name, OS);
   int Fields = int(!Section.Languages.empty()) + int(!Section.Tools.empty()) +
                int(!Section.SDKs.empty());
   if (Fields == 0)
-    return 0;
+    return;
   encodeULEB128(Fields, OS);
   for (auto &Field : {std::make_pair(StringRef("language"), &Section.Languages),
                       std::make_pair(StringRef("processed-by"), &Section.Tools),
@@ -283,52 +290,44 @@ int WasmWriter::writeSectionContent(raw_ostream &OS,
       writeStringRef(Entry.Version, OS);
     }
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::TargetFeaturesSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::TargetFeaturesSection &Section) {
   writeStringRef(Section.Name, OS);
   encodeULEB128(Section.Features.size(), OS);
   for (auto &E : Section.Features) {
     writeUint8(OS, E.Prefix);
     writeStringRef(E.Name, OS);
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::CustomSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::CustomSection &Section) {
   if (auto S = dyn_cast<WasmYAML::DylinkSection>(&Section)) {
-    if (auto Err = writeSectionContent(OS, *S))
-      return Err;
+    writeSectionContent(OS, *S);
   } else if (auto S = dyn_cast<WasmYAML::NameSection>(&Section)) {
-    if (auto Err = writeSectionContent(OS, *S))
-      return Err;
+    writeSectionContent(OS, *S);
   } else if (auto S = dyn_cast<WasmYAML::LinkingSection>(&Section)) {
-    if (auto Err = writeSectionContent(OS, *S))
-      return Err;
+    writeSectionContent(OS, *S);
   } else if (auto S = dyn_cast<WasmYAML::ProducersSection>(&Section)) {
-    if (auto Err = writeSectionContent(OS, *S))
-      return Err;
+    writeSectionContent(OS, *S);
   } else if (auto S = dyn_cast<WasmYAML::TargetFeaturesSection>(&Section)) {
-    if (auto Err = writeSectionContent(OS, *S))
-      return Err;
+    writeSectionContent(OS, *S);
   } else {
     writeStringRef(Section.Name, OS);
     Section.Payload.writeAsBinary(OS);
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
+void WasmWriter::writeSectionContent(raw_ostream &OS,
                                     WasmYAML::TypeSection &Section) {
   encodeULEB128(Section.Signatures.size(), OS);
   uint32_t ExpectedIndex = 0;
   for (const WasmYAML::Signature &Sig : Section.Signatures) {
     if (Sig.Index != ExpectedIndex) {
-      errs() << "Unexpected type index: " << Sig.Index << "\n";
-      return 1;
+      reportError("unexpected type index: " + Twine(Sig.Index));
+      return;
     }
     ++ExpectedIndex;
     writeUint8(OS, Sig.Form);
@@ -342,10 +341,9 @@ int WasmWriter::writeSectionContent(raw_ostream &OS,
       writeUint8(OS, Sig.ReturnType);
     }
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
+void WasmWriter::writeSectionContent(raw_ostream &OS,
                                     WasmYAML::ImportSection &Section) {
   encodeULEB128(Section.Imports.size(), OS);
   for (const WasmYAML::Import &Import : Section.Imports) {
@@ -375,23 +373,20 @@ int WasmWriter::writeSectionContent(raw_ostream &OS,
       writeLimits(Import.TableImport.TableLimits, OS);
       break;
     default:
-      errs() << "Unknown import type: " << Import.Kind << "\n";
-      return 1;
+      reportError("unknown import type: " +Twine(Import.Kind));
+      return;
     }
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::FunctionSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::FunctionSection &Section) {
   encodeULEB128(Section.FunctionTypes.size(), OS);
-  for (uint32_t FuncType : Section.FunctionTypes) {
+  for (uint32_t FuncType : Section.FunctionTypes)
     encodeULEB128(FuncType, OS);
-  }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
+void WasmWriter::writeSectionContent(raw_ostream &OS,
                                     WasmYAML::ExportSection &Section) {
   encodeULEB128(Section.Exports.size(), OS);
   for (const WasmYAML::Export &Export : Section.Exports) {
@@ -399,83 +394,74 @@ int WasmWriter::writeSectionContent(raw_ostream &OS,
     writeUint8(OS, Export.Kind);
     encodeULEB128(Export.Index, OS);
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::StartSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::StartSection &Section) {
   encodeULEB128(Section.StartFunction, OS);
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::TableSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::TableSection &Section) {
   encodeULEB128(Section.Tables.size(), OS);
   for (auto &Table : Section.Tables) {
     writeUint8(OS, Table.ElemType);
     writeLimits(Table.TableLimits, OS);
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::MemorySection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::MemorySection &Section) {
   encodeULEB128(Section.Memories.size(), OS);
-  for (const WasmYAML::Limits &Mem : Section.Memories) {
+  for (const WasmYAML::Limits &Mem : Section.Memories)
     writeLimits(Mem, OS);
-  }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::GlobalSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::GlobalSection &Section) {
   encodeULEB128(Section.Globals.size(), OS);
   uint32_t ExpectedIndex = NumImportedGlobals;
   for (auto &Global : Section.Globals) {
     if (Global.Index != ExpectedIndex) {
-      errs() << "Unexpected global index: " << Global.Index << "\n";
-      return 1;
+      reportError("unexpected global index: " + Twine(Global.Index));
+      return;
     }
     ++ExpectedIndex;
     writeUint8(OS, Global.Type);
     writeUint8(OS, Global.Mutable);
-    writeInitExpr(Global.InitExpr, OS);
+    writeInitExpr(OS, Global.InitExpr);
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
+void WasmWriter::writeSectionContent(raw_ostream &OS,
                                     WasmYAML::EventSection &Section) {
   encodeULEB128(Section.Events.size(), OS);
   uint32_t ExpectedIndex = NumImportedEvents;
   for (auto &Event : Section.Events) {
     if (Event.Index != ExpectedIndex) {
-      errs() << "Unexpected event index: " << Event.Index << "\n";
-      return 1;
+      reportError("unexpected event index: " + Twine(Event.Index));
+      return;
     }
     ++ExpectedIndex;
     encodeULEB128(Event.Attribute, OS);
     encodeULEB128(Event.SigIndex, OS);
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::ElemSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::ElemSection &Section) {
   encodeULEB128(Section.Segments.size(), OS);
   for (auto &Segment : Section.Segments) {
     encodeULEB128(Segment.TableIndex, OS);
-    writeInitExpr(Segment.Offset, OS);
+    writeInitExpr(OS, Segment.Offset);
 
     encodeULEB128(Segment.Functions.size(), OS);
-    for (auto &Function : Segment.Functions) {
+    for (auto &Function : Segment.Functions)
       encodeULEB128(Function, OS);
-    }
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
+void WasmWriter::writeSectionContent(raw_ostream &OS,
                                     WasmYAML::CodeSection &Section) {
   encodeULEB128(Section.Functions.size(), OS);
   uint32_t ExpectedIndex = NumImportedFunctions;
@@ -483,8 +469,8 @@ int WasmWriter::writeSectionContent(raw_ostream &OS,
     std::string OutString;
     raw_string_ostream StringStream(OutString);
     if (Func.Index != ExpectedIndex) {
-      errs() << "Unexpected function index: " << Func.Index << "\n";
-      return 1;
+      reportError("unexpected function index: " + Twine(Func.Index));
+      return;
     }
     ++ExpectedIndex;
 
@@ -501,31 +487,28 @@ int WasmWriter::writeSectionContent(raw_ostream &OS,
     encodeULEB128(OutString.size(), OS);
     OS << OutString;
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::DataSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::DataSection &Section) {
   encodeULEB128(Section.Segments.size(), OS);
   for (auto &Segment : Section.Segments) {
     encodeULEB128(Segment.InitFlags, OS);
     if (Segment.InitFlags & wasm::WASM_SEGMENT_HAS_MEMINDEX)
       encodeULEB128(Segment.MemoryIndex, OS);
     if ((Segment.InitFlags & wasm::WASM_SEGMENT_IS_PASSIVE) == 0)
-      writeInitExpr(Segment.Offset, OS);
+      writeInitExpr(OS, Segment.Offset);
     encodeULEB128(Segment.Content.binary_size(), OS);
     Segment.Content.writeAsBinary(OS);
   }
-  return 0;
 }
 
-int WasmWriter::writeSectionContent(raw_ostream &OS,
-                                    WasmYAML::DataCountSection &Section) {
+void WasmWriter::writeSectionContent(raw_ostream &OS,
+                                     WasmYAML::DataCountSection &Section) {
   encodeULEB128(Section.Count, OS);
-  return 0;
 }
 
-int WasmWriter::writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec,
+void WasmWriter::writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec,
                                   uint32_t SectionIndex) {
   switch (Sec.Type) {
   case wasm::WASM_SEC_CODE:
@@ -541,7 +524,6 @@ int WasmWriter::writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec,
   }
   default:
     llvm_unreachable("not yet implemented");
-    return 1;
   }
 
   encodeULEB128(SectionIndex, OS);
@@ -560,7 +542,6 @@ int WasmWriter::writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec,
       encodeULEB128(Reloc.Addend, OS);
     }
   }
-  return 0;
 }
 
 bool WasmWriter::writeWasm(raw_ostream &OS) {
@@ -575,58 +556,46 @@ bool WasmWriter::writeWasm(raw_ostream &OS) {
     if (auto S = dyn_cast<WasmYAML::CustomSection>(Sec.get()))
       SecName = S->Name;
     if (!Checker.isValidSectionOrder(Sec->Type, SecName)) {
-      errs() << "Out of order section type: " << Sec->Type << "\n";
+      reportError("out of order section type: " + Twine(Sec->Type));
       return false;
     }
     encodeULEB128(Sec->Type, OS);
     std::string OutString;
     raw_string_ostream StringStream(OutString);
-    if (auto S = dyn_cast<WasmYAML::CustomSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::TypeSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::ImportSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::FunctionSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::TableSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::MemorySection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::GlobalSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::EventSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::ExportSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::StartSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::ElemSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::CodeSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::DataSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else if (auto S = dyn_cast<WasmYAML::DataCountSection>(Sec.get())) {
-      if (auto Err = writeSectionContent(StringStream, *S))
-        return Err;
-    } else {
-      errs() << "Unknown section type: " << Sec->Type << "\n";
+    if (auto S = dyn_cast<WasmYAML::CustomSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::TypeSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::ImportSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::FunctionSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::TableSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::MemorySection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::GlobalSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::EventSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::ExportSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::StartSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::ElemSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::CodeSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::DataSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else if (auto S = dyn_cast<WasmYAML::DataCountSection>(Sec.get()))
+      writeSectionContent(StringStream, *S);
+    else
+      reportError("unknown section type: " + Twine(Sec->Type));
+
+    if (HasError)
       return false;
-    }
+
     StringStream.flush();
 
     // Write the section size followed by the content
@@ -658,8 +627,8 @@ bool WasmWriter::writeWasm(raw_ostream &OS) {
 namespace llvm {
 namespace yaml {
 
-bool yaml2wasm(WasmYAML::Object &Doc, raw_ostream &Out) {
-  WasmWriter Writer(Doc);
+bool yaml2wasm(WasmYAML::Object &Doc, raw_ostream &Out, ErrorHandler EH) {
+  WasmWriter Writer(Doc, EH);
   return Writer.writeWasm(Out);
 }
 

lib/ObjectYAML/yaml2obj.cpp

@@ -8,59 +8,69 @@
 
 #include "llvm/ObjectYAML/yaml2obj.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/Twine.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/ObjectYAML/ObjectYAML.h"
 #include "llvm/Support/Errc.h"
+#include "llvm/Support/WithColor.h"
 #include "llvm/Support/YAMLTraits.h"
 
 namespace llvm {
 namespace yaml {
 
-Error convertYAML(yaml::Input &YIn, raw_ostream &Out, unsigned DocNum) {
-  auto BoolToErr = [](bool Ret) -> Error {
-    if (!Ret)
-      return createStringError(errc::invalid_argument, "yaml2obj failed");
-    return Error::success();
-  };
-
+bool convertYAML(yaml::Input &YIn, raw_ostream &Out, ErrorHandler ErrHandler,
+                 unsigned DocNum) {
   unsigned CurDocNum = 0;
   do {
-    if (++CurDocNum == DocNum) {
-      yaml::YamlObjectFile Doc;
-      YIn >> Doc;
-      if (std::error_code EC = YIn.error())
-        return createStringError(EC, "Failed to parse YAML input!");
-      if (Doc.Elf)
-        return BoolToErr(yaml2elf(*Doc.Elf, Out));
-      if (Doc.Coff)
-        return BoolToErr(yaml2coff(*Doc.Coff, Out));
-      if (Doc.MachO || Doc.FatMachO)
-        return BoolToErr(yaml2macho(Doc, Out));
-      if (Doc.Minidump)
-        return BoolToErr(yaml2minidump(*Doc.Minidump, Out));
-      if (Doc.Wasm)
-        return BoolToErr(yaml2wasm(*Doc.Wasm, Out));
-      return createStringError(errc::invalid_argument,
-                               "Unknown document type!");
+    if (++CurDocNum != DocNum)
+      continue;
+
+    yaml::YamlObjectFile Doc;
+    YIn >> Doc;
+    if (std::error_code EC = YIn.error()) {
+      ErrHandler("failed to parse YAML input: " + EC.message());
+      return false;
     }
+
+    if (Doc.Elf)
+      return yaml2elf(*Doc.Elf, Out, ErrHandler);
+    if (Doc.Coff)
+      return yaml2coff(*Doc.Coff, Out, ErrHandler);
+    if (Doc.MachO || Doc.FatMachO)
+      return yaml2macho(Doc, Out, ErrHandler);
+    if (Doc.Minidump)
+      return yaml2minidump(*Doc.Minidump, Out, ErrHandler);
+    if (Doc.Wasm)
+      return yaml2wasm(*Doc.Wasm, Out, ErrHandler);
+
+    ErrHandler("unknown document type");
+    return false;
+
   } while (YIn.nextDocument());
 
-  return createStringError(errc::invalid_argument,
-                           "Cannot find the %u%s document", DocNum,
-                           getOrdinalSuffix(DocNum).data());
+  ErrHandler("cannot find the " + Twine(DocNum) +
+             getOrdinalSuffix(DocNum).data() + " document");
+  return false;
 }
 
-Expected<std::unique_ptr<object::ObjectFile>>
-yaml2ObjectFile(SmallVectorImpl<char> &Storage, StringRef Yaml) {
+std::unique_ptr<object::ObjectFile>
+yaml2ObjectFile(SmallVectorImpl<char> &Storage, StringRef Yaml,
+                ErrorHandler ErrHandler) {
   Storage.clear();
   raw_svector_ostream OS(Storage);
 
   yaml::Input YIn(Yaml);
-  if (Error E = convertYAML(YIn, OS))
-    return std::move(E);
+  if (!convertYAML(YIn, OS, ErrHandler))
+    return {};
+
+  Expected<std::unique_ptr<object::ObjectFile>> ObjOrErr =
+      object::ObjectFile::createObjectFile(
+          MemoryBufferRef(OS.str(), "YamlObject"));
+  if (ObjOrErr)
+    return std::move(*ObjOrErr);
 
-  return object::ObjectFile::createObjectFile(
-      MemoryBufferRef(OS.str(), "YamlObject"));
+  ErrHandler(toString(ObjOrErr.takeError()));
+  return {};
 }
 
 } // namespace yaml

test/ObjectYAML/wasm/invalid_section_order.yaml

@@ -14,7 +14,7 @@ Sections:
       - Index:           0
         Locals:          []
         Body:            0B
-  # CHECK: Out of order section type: 3
+  # CHECK: yaml2obj: error: out of order section type: 3
   - Type:            FUNCTION
     FunctionTypes:   [ 0 ]
 ...

test/tools/yaml2obj/coff-invalid-alignment.test

@@ -1,6 +1,6 @@
 # RUN: not yaml2obj %s 2>&1 | FileCheck %s
 
-## CHECK: Section alignment is too large
+## CHECK: error: section alignment is too large
 
 --- !COFF
 header:

test/tools/yaml2obj/dynsymtab-implicit-sections-size-content.yaml

@@ -31,8 +31,7 @@ DynamicSymbols:
 
 # RUN: not yaml2obj --docnum=2 %s 2>&1 | FileCheck %s --implicit-check-not=error --check-prefix=CASE2
 
-# CASE2: error: cannot specify both `Size` and `DynamicSymbols` for symbol table section '.dynsym'
-# CASE2: error: yaml2obj failed
+# CASE2: yaml2obj: error: cannot specify both `Size` and `DynamicSymbols` for symbol table section '.dynsym'
 
 --- !ELF
 FileHeader:
@@ -55,8 +54,7 @@ DynamicSymbols:
 
 # RUN: not yaml2obj --docnum=3 %s 2>&1 | FileCheck %s --implicit-check-not=error --check-prefix=CASE3
 
-# CASE3: error: cannot specify both `Content` and `DynamicSymbols` for symbol table section '.dynsym'
-# CASE3: error: yaml2obj failed
+# CASE3: yaml2obj: error: cannot specify both `Content` and `DynamicSymbols` for symbol table section '.dynsym'
 
 --- !ELF
 FileHeader:

test/tools/yaml2obj/empty-or-invalid-doc.yaml

@@ -2,7 +2,7 @@
 # RUN: echo -n "" | not yaml2obj 2>&1 | FileCheck %s
 # RUN: echo " " | not yaml2obj 2>&1 | FileCheck %s
 # RUN: echo "  " | not yaml2obj 2>&1 | FileCheck %s
-# CHECK: error: Unknown document type!
+# CHECK: yaml2obj: error: unknown document type
 
 # RUN: echo -e -n "\xff" | not yaml2obj 2>&1 | FileCheck %s --check-prefix=INVALID
-# INVALID: error: Failed to parse YAML input!
+# INVALID: yaml2obj: error: failed to parse YAML input

test/tools/yaml2obj/invalid-docnum.test

@@ -2,10 +2,10 @@
 ## greater than the number of YAML inputs in the file.
 
 # RUN: not yaml2obj %s --docnum=3 2>&1 | FileCheck %s
-# CHECK: error: Cannot find the 3rd document
+# CHECK: yaml2obj: error: cannot find the 3rd document
 
 # RUN: not yaml2obj %s --docnum=76768677 2>&1 | FileCheck %s --check-prefix=TWO
-# TWO: error: Cannot find the 76768677th document
+# TWO: yaml2obj: error: cannot find the 76768677th document
 
 --- !ELF
 FileHeader:

test/tools/yaml2obj/invalid_output_file.test

@@ -1,4 +1,4 @@
 # RUN: not yaml2obj -o %p/path/does/not/exist 2>&1 | FileCheck %s
 
 # Don't check the OS-dependent message "No such file or directory".
-# CHECK: yaml2obj: Error opening '{{.*}}/path/does/not/exist': {{.*}}
+# CHECK: yaml2obj: error: failed to open '{{.*}}/path/does/not/exist': {{.*}}

test/tools/yaml2obj/missing_document_tag.yaml

@@ -6,4 +6,4 @@ DummyData:
 ...
 
 # CHECK: YAML:4:1: error: YAML Object File missing document type tag!
-# CHECK: error: Failed to parse YAML input!
+# CHECK: error: failed to parse YAML input

test/tools/yaml2obj/multi-doc.test

@@ -16,7 +16,7 @@
 # DOC2: Name: _sym2
 # DOC3: Name: _sym3
 # DOC4: Name: _sym4
-# DOC5: error: Cannot find the 5th document
+# DOC5: error: cannot find the 5th document
 
 --- !ELF
 FileHeader: !FileHeader

test/tools/yaml2obj/reloc-sec-info.yaml

@@ -30,7 +30,6 @@ Sections:
 
 # ERR: error: unknown section referenced: '.unknown1' by YAML section '.foo'
 # ERR: error: unknown section referenced: '.unknown2' by YAML section '.bar'
-# ERR: error: yaml2obj failed
 
 --- !ELF
 FileHeader:

test/tools/yaml2obj/section-size-content.yaml

@@ -175,4 +175,4 @@ Sections:
 # ERR2:      error: Section size must be greater than or equal to the content size
 # ERR2-NEXT: - Name: .data
 # ERR2-NEXT:   ^
-# ERR2-NEXT: error: Failed to parse YAML input!
+# ERR2-NEXT: error: failed to parse YAML input

tools/llvm-ifs/llvm-ifs.cpp

@@ -376,12 +376,10 @@ int writeElfStub(const llvm::Triple &T, const std::set<IFSSymbol> &Symbols,
   });
 
   yaml::Input YIn(YamlStr);
-  if (Error E = convertYAML(YIn, Out)) {
-    logAllUnhandledErrors(std::move(E), WithColor::error(errs(), "llvm-ifs"));
-    return 1;
-  }
-
-  return 0;
+  auto ErrHandler = [](const Twine &Msg) {
+    WithColor::error(errs(), "llvm-ifs") << Msg << "\n";
+  };
+  return convertYAML(YIn, Out, ErrHandler) ? 0 : 1;
 }
 
 int writeIfso(const IFSStub &Stub, bool IsWriteIfs, raw_ostream &Out) {

tools/yaml2obj/yaml2obj.cpp

@@ -38,11 +38,6 @@ DocNum("docnum", cl::init(1),
 static cl::opt<std::string> OutputFilename("o", cl::desc("Output filename"),
                                            cl::value_desc("filename"));
 
-LLVM_ATTRIBUTE_NORETURN static void error(Twine Message) {
-  errs() << Message << "\n";
-  exit(1);
-}
-
 int main(int argc, char **argv) {
   InitLLVM X(argc, argv);
   cl::ParseCommandLineOptions(argc, argv);
@@ -50,11 +45,17 @@ int main(int argc, char **argv) {
   if (OutputFilename.empty())
     OutputFilename = "-";
 
+  auto ErrHandler = [](const Twine &Msg) {
+    WithColor::error(errs(), "yaml2obj") << Msg << "\n";
+  };
+
   std::error_code EC;
   std::unique_ptr<ToolOutputFile> Out(
       new ToolOutputFile(OutputFilename, EC, sys::fs::OF_None));
-  if (EC)
-    error("yaml2obj: Error opening '" + OutputFilename + "': " + EC.message());
+  if (EC) {
+    ErrHandler("failed to open '" + OutputFilename + "': " + EC.message());
+    return 1;
+  }
 
   ErrorOr<std::unique_ptr<MemoryBuffer>> Buf =
       MemoryBuffer::getFileOrSTDIN(Input);
@@ -62,10 +63,8 @@ int main(int argc, char **argv) {
     return 1;
 
   yaml::Input YIn(Buf.get()->getBuffer());
-  if (Error E = convertYAML(YIn, Out->os(), DocNum)) {
-    logAllUnhandledErrors(std::move(E), WithColor::error(errs(), argv[0]));
+  if (!convertYAML(YIn, Out->os(), ErrHandler, DocNum))
     return 1;
-  }
 
   Out->keep();
   Out->os().flush();

unittests/ObjectYAML/MinidumpYAMLTest.cpp

@@ -20,8 +20,9 @@ toBinary(SmallVectorImpl<char> &Storage, StringRef Yaml) {
   Storage.clear();
   raw_svector_ostream OS(Storage);
   yaml::Input YIn(Yaml);
-  if (Error E = yaml::convertYAML(YIn, OS))
-    return std::move(E);
+  if (!yaml::convertYAML(YIn, OS, [](const Twine &Msg) {}))
+    return createStringError(std::errc::invalid_argument,
+                             "unable to convert YAML");
 
   return object::MinidumpFile::create(MemoryBufferRef(OS.str(), "Binary"));
 }

unittests/ObjectYAML/YAML2ObjTest.cpp

@@ -10,6 +10,7 @@
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Support/Error.h"
+#include "llvm/Support/YAMLTraits.h"
 #include "llvm/Testing/Support/Error.h"
 #include "gtest/gtest.h"
 
@@ -18,19 +19,63 @@ using namespace object;
 using namespace yaml;
 
 TEST(yaml2ObjectFile, ELF) {
+  bool ErrorReported = false;
+  auto ErrHandler = [&](const Twine &Msg) { ErrorReported = true; };
+
+  SmallString<0> Storage;
+  std::unique_ptr<ObjectFile> Obj = yaml2ObjectFile(Storage, R"(
+--- !ELF
+FileHeader:
+  Class:    ELFCLASS64
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_X86_64)", ErrHandler);
+
+  ASSERT_FALSE(ErrorReported);
+  ASSERT_TRUE(Obj);
+  ASSERT_TRUE(Obj->isELF());
+  ASSERT_TRUE(Obj->isRelocatableObject());
+}
+
+TEST(yaml2ObjectFile, Errors) {
+  std::vector<std::string> Errors;
+  auto ErrHandler = [&](const Twine &Msg) {
+    Errors.push_back("ObjectYAML: " + Msg.str());
+  };
+
   SmallString<0> Storage;
-  Expected<std::unique_ptr<ObjectFile>> ErrOrObj = yaml2ObjectFile(Storage, R"(
+  StringRef Yaml = R"(
 --- !ELF
 FileHeader:
   Class:    ELFCLASS64
   Data:     ELFDATA2LSB
   Type:     ET_REL
-  Machine:  EM_X86_64)");
+  Machine:  EM_X86_64
+Symbols:
+  - Name: foo
+  - Name: foo
+  - Name: foo
+)";
+
+  // 1. Test yaml2ObjectFile().
+
+  std::unique_ptr<ObjectFile> Obj = yaml2ObjectFile(Storage, Yaml, ErrHandler);
+
+  ASSERT_FALSE(Obj);
+  ASSERT_TRUE(Errors.size() == 2);
+  ASSERT_TRUE(Errors[0] == "ObjectYAML: repeated symbol name: 'foo'");
+  ASSERT_TRUE(Errors[1] == Errors[0]);
 
-  ASSERT_THAT_EXPECTED(ErrOrObj, Succeeded());
+  // 2. Test convertYAML(). 
 
-  std::unique_ptr<ObjectFile> ObjFile = std::move(ErrOrObj.get());
+  Errors.clear();
+  Storage.clear();
+  raw_svector_ostream OS(Storage);
 
-  ASSERT_TRUE(ObjFile->isELF());
-  ASSERT_TRUE(ObjFile->isRelocatableObject());
+  yaml::Input YIn(Yaml);
+  bool Res = convertYAML(YIn, OS, ErrHandler);
+  ASSERT_FALSE(Res);
+  ASSERT_TRUE(Errors.size() == 2);
+  ASSERT_TRUE(Errors[0] == "ObjectYAML: repeated symbol name: 'foo'");
+  ASSERT_TRUE(Errors[1] == Errors[0]);
 }