Fix Mac Breakpad host tools to build in Linux cross-compile

We're working on building our Firefox Mac builds as a Linux cross-compile
(https://bugzilla.mozilla.org/show_bug.cgi?id=921040) and we need symbol
dumping to work. This change ports the Mac dump_syms tool to build and work
on Linux. I've tested it and it produces identical output to running the
tool on Mac.

The bulk of the work here was converting src/common/mac/dump_syms.mm and
src/tools/mac/dump_syms/dump_syms_tool.mm from ObjC++ to C++ and removing
their use of Foundation classes in favor of standard C/C++.

This won't compile out-of-the-box on Linux, it requires some Mac system
headers that are not included in this patch. I have those tentatively in
a separate patch to land in Gecko
(http://hg.mozilla.org/users/tmielczarek_mozilla.com/mc/rev/5fb8da23c83c),
but I wasn't sure if you'd be interested in having them in the Breakpad tree.
We could almost certainly pare down the set of headers included there, I
didn't spend too much time trying to minimize them (we primarily just need
the Mach-O structs and a few associated bits).

I just realized that this patch is missing updating the XCode project files
(ugh). I'll fix that up in a bit.

R=mark@chromium.org
BUG=https://bugzilla.mozilla.org/show_bug.cgi?id=543111

Review URL: https://codereview.chromium.org/1340543002 .

1 files changed, 626 insertions, 0 deletions

diff --git a/src/common/mac/dump_syms.cc b/src/common/mac/dump_syms.cc
new file mode 100644
index 00000000..4dcdb73e
--- /dev/null
+++ b/src/common/mac/dump_syms.cc
@@ -0,0 +1,626 @@
+// -*- mode: c++ -*-
+
+// Copyright (c) 2011, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// dump_syms.mm: Create a symbol file for use with minidumps
+
+#include "common/mac/dump_syms.h"
+
+#include <assert.h>
+#include <dirent.h>
+#include <errno.h>
+#include <libgen.h>
+#include <mach-o/arch.h>
+#include <mach-o/fat.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <ostream>
+#include <string>
+#include <vector>
+
+#include "common/dwarf/bytereader-inl.h"
+#include "common/dwarf/dwarf2reader.h"
+#include "common/dwarf_cfi_to_module.h"
+#include "common/dwarf_cu_to_module.h"
+#include "common/dwarf_line_to_module.h"
+#include "common/mac/file_id.h"
+#include "common/mac/arch_utilities.h"
+#include "common/mac/macho_reader.h"
+#include "common/module.h"
+#include "common/scoped_ptr.h"
+#include "common/stabs_reader.h"
+#include "common/stabs_to_module.h"
+#include "common/symbol_data.h"
+
+#ifndef CPU_TYPE_ARM
+#define CPU_TYPE_ARM (static_cast<cpu_type_t>(12))
+#endif //  CPU_TYPE_ARM
+
+#ifndef CPU_TYPE_ARM64
+#define CPU_TYPE_ARM64 (static_cast<cpu_type_t>(16777228))
+#endif  // CPU_TYPE_ARM64
+
+using dwarf2reader::ByteReader;
+using google_breakpad::DwarfCUToModule;
+using google_breakpad::DwarfLineToModule;
+using google_breakpad::FileID;
+using google_breakpad::mach_o::FatReader;
+using google_breakpad::mach_o::Section;
+using google_breakpad::mach_o::Segment;
+using google_breakpad::Module;
+using google_breakpad::StabsReader;
+using google_breakpad::StabsToModule;
+using google_breakpad::scoped_ptr;
+using std::make_pair;
+using std::pair;
+using std::string;
+using std::vector;
+
+namespace {
+// Return a vector<string> with absolute paths to all the entries
+// in directory (excluding . and ..).
+vector<string> list_directory(const string& directory) {
+  vector<string> entries;
+  DIR* dir = opendir(directory.c_str());
+  if (!dir) {
+    return entries;
+  }
+
+  string path = directory;
+  if (path[path.length() - 1] != '/') {
+    path += '/';
+  }
+
+  struct dirent* entry = NULL;
+  while ((entry = readdir(dir))) {
+    if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
+      entries.push_back(path + entry->d_name);
+    }
+  }
+
+  closedir(dir);
+  return entries;
+}
+}
+
+namespace google_breakpad {
+
+bool DumpSymbols::Read(const string &filename) {
+  struct stat st;
+  if (stat(filename.c_str(), &st) == -1) {
+    fprintf(stderr, "Could not access object file %s: %s\n",
+            filename.c_str(), strerror(errno));
+    return false;
+  }
+
+  input_pathname_ = filename;
+
+  // Does this filename refer to a dSYM bundle?
+  string contents_path = input_pathname_ + "/Contents/Resources/DWARF";
+  if (S_ISDIR(st.st_mode) &&
+      access(contents_path.c_str(), F_OK) == 0) {
+    // If there's one file under Contents/Resources/DWARF then use that,
+    // otherwise bail out.
+    const vector<string> entries = list_directory(contents_path);
+    if (entries.size() == 0) {
+      fprintf(stderr, "Unable to find DWARF-bearing file in bundle: %s\n",
+              input_pathname_.c_str());
+      return false;
+    }
+    if (entries.size() > 1) {
+      fprintf(stderr, "Too many DWARF files in bundle: %s\n",
+              input_pathname_.c_str());
+      return false;
+    }
+
+    object_filename_ = entries[0];
+  } else {
+    object_filename_ = input_pathname_;
+  }
+
+  // Read the file's contents into memory.
+  bool read_ok = true;
+  string error;
+  if (stat(object_filename_.c_str(), &st) != -1) {
+    FILE* f = fopen(object_filename_.c_str(), "rb");
+    if (f) {
+      contents_.reset(new uint8_t[st.st_size]);
+      off_t total = 0;
+      while (total < st.st_size && !feof(f)) {
+        size_t read = fread(&contents_[0] + total, 1, st.st_size - total, f);
+        if (read == 0) {
+          if (ferror(f)) {
+            read_ok = false;
+            error = strerror(errno);
+          }
+          break;
+        }
+        total += read;
+      }
+      fclose(f);
+    } else {
+      error = strerror(errno);
+    }
+  }
+
+  if (!read_ok) {
+    fprintf(stderr, "Error reading object file: %s: %s\n",
+            object_filename_.c_str(),
+            error.c_str());
+    return false;
+  }
+
+  // Get the list of object files present in the file.
+  FatReader::Reporter fat_reporter(object_filename_);
+  FatReader fat_reader(&fat_reporter);
+  if (!fat_reader.Read(&contents_[0],
+                       st.st_size)) {
+    return false;
+  }
+
+  // Get our own copy of fat_reader's object file list.
+  size_t object_files_count;
+  const SuperFatArch *object_files =
+    fat_reader.object_files(&object_files_count);
+  if (object_files_count == 0) {
+    fprintf(stderr, "Fat binary file contains *no* architectures: %s\n",
+            object_filename_.c_str());
+    return false;
+  }
+  object_files_.resize(object_files_count);
+  memcpy(&object_files_[0], object_files,
+         sizeof(SuperFatArch) * object_files_count);
+
+  return true;
+}
+
+bool DumpSymbols::SetArchitecture(cpu_type_t cpu_type,
+                                  cpu_subtype_t cpu_subtype) {
+  // Find the best match for the architecture the user requested.
+  const SuperFatArch *best_match = FindBestMatchForArchitecture(
+      cpu_type, cpu_subtype);
+  if (!best_match) return false;
+
+  // Record the selected object file.
+  selected_object_file_ = best_match;
+  return true;
+}
+
+bool DumpSymbols::SetArchitecture(const std::string &arch_name) {
+  bool arch_set = false;
+  const NXArchInfo *arch_info =
+      google_breakpad::BreakpadGetArchInfoFromName(arch_name.c_str());
+  if (arch_info) {
+    arch_set = SetArchitecture(arch_info->cputype, arch_info->cpusubtype);
+  }
+  return arch_set;
+}
+
+SuperFatArch* DumpSymbols::FindBestMatchForArchitecture(
+    cpu_type_t cpu_type, cpu_subtype_t cpu_subtype) {
+  // Check if all the object files can be converted to struct fat_arch.
+  bool can_convert_to_fat_arch = true;
+  vector<struct fat_arch> fat_arch_vector;
+  for (vector<SuperFatArch>::const_iterator it = object_files_.begin();
+       it != object_files_.end();
+       ++it) {
+    struct fat_arch arch;
+    bool success = it->ConvertToFatArch(&arch);
+    if (!success) {
+      can_convert_to_fat_arch = false;
+      break;
+    }
+    fat_arch_vector.push_back(arch);
+  }
+
+  // If all the object files can be converted to struct fat_arch, use
+  // NXFindBestFatArch.
+  if (can_convert_to_fat_arch) {
+    const struct fat_arch *best_match
+      = NXFindBestFatArch(cpu_type, cpu_subtype, &fat_arch_vector[0],
+                          static_cast<uint32_t>(fat_arch_vector.size()));
+
+    for (size_t i = 0; i < fat_arch_vector.size(); ++i) {
+      if (best_match == &fat_arch_vector[i])
+        return &object_files_[i];
+    }
+    assert(best_match == NULL);
+    return NULL;
+  }
+
+  // Check for an exact match with cpu_type and cpu_subtype.
+  for (vector<SuperFatArch>::iterator it = object_files_.begin();
+       it != object_files_.end();
+       ++it) {
+    if (static_cast<cpu_type_t>(it->cputype) == cpu_type &&
+        static_cast<cpu_subtype_t>(it->cpusubtype) == cpu_subtype)
+      return &*it;
+  }
+
+  // No exact match found.
+  // TODO(erikchen): If it becomes necessary, we can copy the implementation of
+  // NXFindBestFatArch, located at
+  // http://web.mit.edu/darwin/src/modules/cctools/libmacho/arch.c.
+  fprintf(stderr, "Failed to find an exact match for an object file with cpu "
+      "type: %d and cpu subtype: %d. Furthermore, at least one object file is "
+      "larger than 2**32.\n", cpu_type, cpu_subtype);
+  return NULL;
+}
+
+string DumpSymbols::Identifier() {
+  FileID file_id(object_filename_.c_str());
+  unsigned char identifier_bytes[16];
+  cpu_type_t cpu_type = selected_object_file_->cputype;
+  cpu_subtype_t cpu_subtype = selected_object_file_->cpusubtype;
+  if (!file_id.MachoIdentifier(cpu_type, cpu_subtype, identifier_bytes)) {
+    fprintf(stderr, "Unable to calculate UUID of mach-o binary %s!\n",
+            object_filename_.c_str());
+    return "";
+  }
+
+  char identifier_string[40];
+  FileID::ConvertIdentifierToString(identifier_bytes, identifier_string,
+                                    sizeof(identifier_string));
+
+  string compacted(identifier_string);
+  for(size_t i = compacted.find('-'); i != string::npos;
+      i = compacted.find('-', i))
+    compacted.erase(i, 1);
+
+  return compacted;
+}
+
+// A line-to-module loader that accepts line number info parsed by
+// dwarf2reader::LineInfo and populates a Module and a line vector
+// with the results.
+class DumpSymbols::DumperLineToModule:
+      public DwarfCUToModule::LineToModuleHandler {
+ public:
+  // Create a line-to-module converter using BYTE_READER.
+  DumperLineToModule(dwarf2reader::ByteReader *byte_reader)
+      : byte_reader_(byte_reader) { }
+
+  void StartCompilationUnit(const string& compilation_dir) {
+    compilation_dir_ = compilation_dir;
+  }
+
+  void ReadProgram(const char *program, uint64 length,
+                   Module *module, vector<Module::Line> *lines) {
+    DwarfLineToModule handler(module, compilation_dir_, lines);
+    dwarf2reader::LineInfo parser(program, length, byte_reader_, &handler);
+    parser.Start();
+  }
+ private:
+  string compilation_dir_;
+  dwarf2reader::ByteReader *byte_reader_;  // WEAK
+};
+
+bool DumpSymbols::ReadDwarf(google_breakpad::Module *module,
+                            const mach_o::Reader &macho_reader,
+                            const mach_o::SectionMap &dwarf_sections,
+                            bool handle_inter_cu_refs) const {
+  // Build a byte reader of the appropriate endianness.
+  ByteReader byte_reader(macho_reader.big_endian()
+                         ? dwarf2reader::ENDIANNESS_BIG
+                         : dwarf2reader::ENDIANNESS_LITTLE);
+
+  // Construct a context for this file.
+  DwarfCUToModule::FileContext file_context(selected_object_name_,
+                                            module,
+                                            handle_inter_cu_refs);
+
+  // Build a dwarf2reader::SectionMap from our mach_o::SectionMap.
+  for (mach_o::SectionMap::const_iterator it = dwarf_sections.begin();
+       it != dwarf_sections.end(); ++it) {
+    file_context.AddSectionToSectionMap(
+        it->first,
+        reinterpret_cast<const char *>(it->second.contents.start),
+        it->second.contents.Size());
+  }
+
+  // Find the __debug_info section.
+  dwarf2reader::SectionMap::const_iterator debug_info_entry =
+      file_context.section_map().find("__debug_info");
+  assert(debug_info_entry != file_context.section_map().end());
+  const std::pair<const char*, uint64>& debug_info_section =
+      debug_info_entry->second;
+  // There had better be a __debug_info section!
+  if (!debug_info_section.first) {
+    fprintf(stderr, "%s: __DWARF segment of file has no __debug_info section\n",
+            selected_object_name_.c_str());
+    return false;
+  }
+
+  // Build a line-to-module loader for the root handler to use.
+  DumperLineToModule line_to_module(&byte_reader);
+
+  // Walk the __debug_info section, one compilation unit at a time.
+  uint64 debug_info_length = debug_info_section.second;
+  for (uint64 offset = 0; offset < debug_info_length;) {
+    // Make a handler for the root DIE that populates MODULE with the
+    // debug info.
+    DwarfCUToModule::WarningReporter reporter(selected_object_name_,
+                                              offset);
+    DwarfCUToModule root_handler(&file_context, &line_to_module, &reporter);
+    // Make a Dwarf2Handler that drives our DIEHandler.
+    dwarf2reader::DIEDispatcher die_dispatcher(&root_handler);
+    // Make a DWARF parser for the compilation unit at OFFSET.
+    dwarf2reader::CompilationUnit dwarf_reader(file_context.section_map(),
+                                               offset,
+                                               &byte_reader,
+                                               &die_dispatcher);
+    // Process the entire compilation unit; get the offset of the next.
+    offset += dwarf_reader.Start();
+  }
+
+  return true;
+}
+
+bool DumpSymbols::ReadCFI(google_breakpad::Module *module,
+                          const mach_o::Reader &macho_reader,
+                          const mach_o::Section &section,
+                          bool eh_frame) const {
+  // Find the appropriate set of register names for this file's
+  // architecture.
+  vector<string> register_names;
+  switch (macho_reader.cpu_type()) {
+    case CPU_TYPE_X86:
+      register_names = DwarfCFIToModule::RegisterNames::I386();
+      break;
+    case CPU_TYPE_X86_64:
+      register_names = DwarfCFIToModule::RegisterNames::X86_64();
+      break;
+    case CPU_TYPE_ARM:
+      register_names = DwarfCFIToModule::RegisterNames::ARM();
+      break;
+    case CPU_TYPE_ARM64:
+      register_names = DwarfCFIToModule::RegisterNames::ARM64();
+      break;
+    default: {
+      const NXArchInfo *arch = google_breakpad::BreakpadGetArchInfoFromCpuType(
+          macho_reader.cpu_type(), macho_reader.cpu_subtype());
+      fprintf(stderr, "%s: cannot convert DWARF call frame information for ",
+              selected_object_name_.c_str());
+      if (arch)
+        fprintf(stderr, "architecture '%s'", arch->name);
+      else
+        fprintf(stderr, "architecture %d,%d",
+                macho_reader.cpu_type(), macho_reader.cpu_subtype());
+      fprintf(stderr, " to Breakpad symbol file: no register name table\n");
+      return false;
+    }
+  }
+
+  // Find the call frame information and its size.
+  const char *cfi = reinterpret_cast<const char *>(section.contents.start);
+  size_t cfi_size = section.contents.Size();
+
+  // Plug together the parser, handler, and their entourages.
+  DwarfCFIToModule::Reporter module_reporter(selected_object_name_,
+                                             section.section_name);
+  DwarfCFIToModule handler(module, register_names, &module_reporter);
+  dwarf2reader::ByteReader byte_reader(macho_reader.big_endian() ?
+                                       dwarf2reader::ENDIANNESS_BIG :
+                                       dwarf2reader::ENDIANNESS_LITTLE);
+  byte_reader.SetAddressSize(macho_reader.bits_64() ? 8 : 4);
+  // At the moment, according to folks at Apple and some cursory
+  // investigation, Mac OS X only uses DW_EH_PE_pcrel-based pointers, so
+  // this is the only base address the CFI parser will need.
+  byte_reader.SetCFIDataBase(section.address, cfi);
+
+  dwarf2reader::CallFrameInfo::Reporter dwarf_reporter(selected_object_name_,
+                                                       section.section_name);
+  dwarf2reader::CallFrameInfo parser(cfi, cfi_size,
+                                     &byte_reader, &handler, &dwarf_reporter,
+                                     eh_frame);
+  parser.Start();
+  return true;
+}
+
+// A LoadCommandHandler that loads whatever debugging data it finds into a
+// Module.
+class DumpSymbols::LoadCommandDumper:
+      public mach_o::Reader::LoadCommandHandler {
+ public:
+  // Create a load command dumper handling load commands from READER's
+  // file, and adding data to MODULE.
+  LoadCommandDumper(const DumpSymbols &dumper,
+                    google_breakpad::Module *module,
+                    const mach_o::Reader &reader,
+                    SymbolData symbol_data,
+                    bool handle_inter_cu_refs)
+      : dumper_(dumper),
+        module_(module),
+        reader_(reader),
+        symbol_data_(symbol_data),
+        handle_inter_cu_refs_(handle_inter_cu_refs) { }
+
+  bool SegmentCommand(const mach_o::Segment &segment);
+  bool SymtabCommand(const ByteBuffer &entries, const ByteBuffer &strings);
+
+ private:
+  const DumpSymbols &dumper_;
+  google_breakpad::Module *module_;  // WEAK
+  const mach_o::Reader &reader_;
+  const SymbolData symbol_data_;
+  const bool handle_inter_cu_refs_;
+};
+
+bool DumpSymbols::LoadCommandDumper::SegmentCommand(const Segment &segment) {
+  mach_o::SectionMap section_map;
+  if (!reader_.MapSegmentSections(segment, &section_map))
+    return false;
+
+  if (segment.name == "__TEXT") {
+    module_->SetLoadAddress(segment.vmaddr);
+    if (symbol_data_ != NO_CFI) {
+      mach_o::SectionMap::const_iterator eh_frame =
+          section_map.find("__eh_frame");
+      if (eh_frame != section_map.end()) {
+        // If there is a problem reading this, don't treat it as a fatal error.
+        dumper_.ReadCFI(module_, reader_, eh_frame->second, true);
+      }
+    }
+    return true;
+  }
+
+  if (segment.name == "__DWARF") {
+    if (symbol_data_ != ONLY_CFI) {
+      if (!dumper_.ReadDwarf(module_, reader_, section_map,
+                             handle_inter_cu_refs_)) {
+        return false;
+      }
+    }
+    if (symbol_data_ != NO_CFI) {
+      mach_o::SectionMap::const_iterator debug_frame
+          = section_map.find("__debug_frame");
+      if (debug_frame != section_map.end()) {
+        // If there is a problem reading this, don't treat it as a fatal error.
+        dumper_.ReadCFI(module_, reader_, debug_frame->second, false);
+      }
+    }
+  }
+
+  return true;
+}
+
+bool DumpSymbols::LoadCommandDumper::SymtabCommand(const ByteBuffer &entries,
+                                                   const ByteBuffer &strings) {
+  StabsToModule stabs_to_module(module_);
+  // Mac OS X STABS are never "unitized", and the size of the 'value' field
+  // matches the address size of the executable.
+  StabsReader stabs_reader(entries.start, entries.Size(),
+                           strings.start, strings.Size(),
+                           reader_.big_endian(),
+                           reader_.bits_64() ? 8 : 4,
+                           true,
+                           &stabs_to_module);
+  if (!stabs_reader.Process())
+    return false;
+  stabs_to_module.Finalize();
+  return true;
+}
+
+bool DumpSymbols::ReadSymbolData(Module** out_module) {
+  // Select an object file, if SetArchitecture hasn't been called to set one
+  // explicitly.
+  if (!selected_object_file_) {
+    // If there's only one architecture, that's the one.
+    if (object_files_.size() == 1)
+      selected_object_file_ = &object_files_[0];
+    else {
+      // Look for an object file whose architecture matches our own.
+      const NXArchInfo *local_arch = NXGetLocalArchInfo();
+      if (!SetArchitecture(local_arch->cputype, local_arch->cpusubtype)) {
+        fprintf(stderr, "%s: object file contains more than one"
+                " architecture, none of which match the current"
+                " architecture; specify an architecture explicitly"
+                " with '-a ARCH' to resolve the ambiguity\n",
+                object_filename_.c_str());
+        return false;
+      }
+    }
+  }
+
+  assert(selected_object_file_);
+
+  // Find the name of the selected file's architecture, to appear in
+  // the MODULE record and in error messages.
+  const NXArchInfo *selected_arch_info =
+      google_breakpad::BreakpadGetArchInfoFromCpuType(
+          selected_object_file_->cputype, selected_object_file_->cpusubtype);
+
+  const char *selected_arch_name = selected_arch_info->name;
+  if (strcmp(selected_arch_name, "i386") == 0)
+    selected_arch_name = "x86";
+
+  // Produce a name to use in error messages that includes the
+  // filename, and the architecture, if there is more than one.
+  selected_object_name_ = object_filename_;
+  if (object_files_.size() > 1) {
+    selected_object_name_ += ", architecture ";
+    selected_object_name_ + selected_arch_name;
+  }
+
+  // Compute a module name, to appear in the MODULE record.
+  string module_name = object_filename_;
+  module_name = basename(&module_name[0]);
+
+  // Choose an identifier string, to appear in the MODULE record.
+  string identifier = Identifier();
+  if (identifier.empty())
+    return false;
+  identifier += "0";
+
+  // Create a module to hold the debugging information.
+  scoped_ptr<Module> module(new Module(module_name,
+                                       "mac",
+                                       selected_arch_name,
+                                       identifier));
+
+  // Parse the selected object file.
+  mach_o::Reader::Reporter reporter(selected_object_name_);
+  mach_o::Reader reader(&reporter);
+  if (!reader.Read(&contents_[0]
+                   + selected_object_file_->offset,
+                   selected_object_file_->size,
+                   selected_object_file_->cputype,
+                   selected_object_file_->cpusubtype))
+    return false;
+
+  // Walk its load commands, and deal with whatever is there.
+  LoadCommandDumper load_command_dumper(*this, module.get(), reader,
+                                        symbol_data_, handle_inter_cu_refs_);
+  if (!reader.WalkLoadCommands(&load_command_dumper))
+    return false;
+
+  *out_module = module.release();
+
+  return true;
+}
+
+bool DumpSymbols::WriteSymbolFile(std::ostream &stream) {
+  Module* module = NULL;
+
+  if (ReadSymbolData(&module) && module) {
+    bool res = module->Write(stream, symbol_data_);
+    delete module;
+    return res;
+  }
+
+  return false;
+}
+
+}  // namespace google_breakpad