Breakpad Mac symbol dumper: Add new Mach-O reader class.

This patch adds files defining new classes in the google_breakpad::Mach_O
namespace for parsing fat binaries and Mach-O files. These are used in the
new dumper to handle STABS debugging information, DWARF call frame
information, and .eh_frame exception handling stack walking information.

These new classes are independent of endianness and word size, and
therefore can be used on binaries of all the relevant architectures: x86,
x86_64, ppc, and ARM.

The patch adds a complete set of unit tests for the new classes.
A=jimb R=mark (http://breakpad.appspot.com/93001/show, http://breakpad.appspot.com/115001/show)

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@610 4c0a9323-5329-0410-9bdc-e9ce6186880e

3 files changed, 2881 insertions, 0 deletions

diff --git a/src/common/mac/macho_reader.cc b/src/common/mac/macho_reader.cc
new file mode 100644
index 00000000..53da1807
--- /dev/null
+++ b/src/common/mac/macho_reader.cc
@@ -0,0 +1,524 @@
+// Copyright (c) 2010, 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.
+
+// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// macho_reader.cc: Implementation of google_breakpad::Mach_O::FatReader and
+// google_breakpad::Mach_O::Reader. See macho_reader.h for details.
+
+#include "common/mac/macho_reader.h"
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+namespace google_breakpad {
+namespace mach_o {
+
+// If NDEBUG is #defined, then the 'assert' macro doesn't evaluate its
+// arguments, so you can't place expressions that do necessary work in
+// the argument of an assert. Nor can you assign the result of the
+// expression to a variable and assert that the variable's value is
+// true: you'll get unused variable warnings when NDEBUG is #defined.
+//
+// ASSERT_ALWAYS_EVAL always evaluates its argument, and asserts that
+// the result is true if NDEBUG is not #defined.
+#if defined(NDEBUG)
+#define ASSERT_ALWAYS_EVAL(x) (x)
+#else
+#define ASSERT_ALWAYS_EVAL(x) assert(x)
+#endif
+
+void FatReader::Reporter::BadHeader() {
+  fprintf(stderr, "%s: file is neither a fat binary file"
+          " nor a Mach-O object file\n", filename_.c_str());
+}
+
+void FatReader::Reporter::TooShort() {
+  fprintf(stderr, "%s: file too short for the data it claims to contain\n",
+          filename_.c_str());
+}
+
+void FatReader::Reporter::MisplacedObjectFile() {
+  fprintf(stderr, "%s: file too short for the object files it claims"
+          " to contain\n", filename_.c_str());
+}
+
+bool FatReader::Read(const uint8_t *buffer, size_t size) {
+  buffer_.start = buffer;
+  buffer_.end = buffer + size;
+  ByteCursor cursor(&buffer_);
+
+  // Fat binaries always use big-endian, so read the magic number in
+  // that endianness. To recognize Mach-O magic numbers, which can use
+  // either endianness, check for both the proper and reversed forms
+  // of the magic numbers.
+  cursor.set_big_endian(true);
+  if (cursor >> magic_) {
+    if (magic_ == FAT_MAGIC) {
+      // How many object files does this fat binary contain?
+      uint32_t object_files_count;
+      if (!(cursor >> object_files_count)) {  // nfat_arch
+        reporter_->TooShort();
+        return false;
+      }
+
+      // Read the list of object files.
+      object_files_.resize(object_files_count);
+      for (size_t i = 0; i < object_files_count; i++) {
+        struct fat_arch *objfile = &object_files_[i];
+
+        // Read this object file entry, byte-swapping as appropriate.
+        cursor >> objfile->cputype
+               >> objfile->cpusubtype
+               >> objfile->offset
+               >> objfile->size
+               >> objfile->align;
+        if (!cursor) {
+          reporter_->TooShort();
+          return false;
+        }
+        // Does the file actually have the bytes this entry refers to?
+        size_t fat_size = buffer_.Size();
+        if (objfile->offset > fat_size ||
+            objfile->size > fat_size - objfile->offset) {
+          reporter_->MisplacedObjectFile();
+          return false;
+        }
+      }
+
+      return true;
+    } else if (magic_ == MH_MAGIC || magic_ == MH_MAGIC_64 ||
+               magic_ == MH_CIGAM || magic_ == MH_CIGAM_64) {
+      // If this is a little-endian Mach-O file, fix the cursor's endianness.
+      if (magic_ == MH_CIGAM || magic_ == MH_CIGAM_64)
+        cursor.set_big_endian(false);
+      // Record the entire file as a single entry in the object file list.
+      object_files_.resize(1);
+
+      // Get the cpu type and subtype from the Mach-O header.
+      if (!(cursor >> object_files_[0].cputype
+                   >> object_files_[0].cpusubtype)) {
+        reporter_->TooShort();
+        return false;
+      }
+
+      object_files_[0].offset = 0;
+      object_files_[0].size = buffer_.Size();
+      // This alignment is correct for 32 and 64-bit x86 and ppc.
+      // See get_align in the lipo source for other architectures:
+      // http://www.opensource.apple.com/source/cctools/cctools-773/misc/lipo.c
+      object_files_[0].align = 12;  // 2^12 == 4096
+      
+      return true;
+    }
+  }
+  
+  reporter_->BadHeader();
+  return false;
+}
+
+void Reader::Reporter::BadHeader() {
+  fprintf(stderr, "%s: file is not a Mach-O object file\n", filename_.c_str());
+}
+
+void Reader::Reporter::CPUTypeMismatch(cpu_type_t cpu_type,
+                                       cpu_subtype_t cpu_subtype,
+                                       cpu_type_t expected_cpu_type,
+                                       cpu_subtype_t expected_cpu_subtype) {
+  fprintf(stderr, "%s: CPU type %d, subtype %d does not match expected"
+          " type %d, subtype %d\n",
+          filename_.c_str(), cpu_type, cpu_subtype,
+          expected_cpu_type, expected_cpu_subtype);
+}
+
+void Reader::Reporter::HeaderTruncated() {
+  fprintf(stderr, "%s: file does not contain a complete Mach-O header\n",
+          filename_.c_str());
+}
+
+void Reader::Reporter::LoadCommandRegionTruncated() {
+  fprintf(stderr, "%s: file too short to hold load command region"
+          " given in Mach-O header\n", filename_.c_str());
+}
+
+void Reader::Reporter::LoadCommandsOverrun(size_t claimed, size_t i,
+                                           LoadCommandType type) {
+  fprintf(stderr, "%s: file's header claims there are %ld"
+          " load commands, but load command #%ld",
+          filename_.c_str(), claimed, i);
+  if (type) fprintf(stderr, ", of type %d,", type);
+  fprintf(stderr, " extends beyond the end of the load command region\n");
+}
+
+void Reader::Reporter::LoadCommandTooShort(size_t i, LoadCommandType type) {
+  fprintf(stderr, "%s: the contents of load command #%ld, of type %d,"
+          " extend beyond the size given in the load command's header\n",
+          filename_.c_str(), i, type);
+}
+
+void Reader::Reporter::SectionsMissing(const string &name) {
+  fprintf(stderr, "%s: the load command for segment '%s'"
+          " is too short to hold the section headers it claims to have\n",
+          filename_.c_str(), name.c_str());
+}
+
+void Reader::Reporter::MisplacedSegmentData(const string &name) {
+  fprintf(stderr, "%s: the segment '%s' claims its contents lie beyond"
+          " the end of the file\n", filename_.c_str(), name.c_str());
+}
+
+void Reader::Reporter::MisplacedSectionData(const string &section,
+                                            const string &segment) {
+  fprintf(stderr, "%s: the section '%s' in segment '%s'"
+          " claims its contents lie outside the segment's contents\n",
+          filename_.c_str(), section.c_str(), segment.c_str());
+}
+
+void Reader::Reporter::MisplacedSymbolTable() {
+  fprintf(stderr, "%s: the LC_SYMTAB load command claims that the symbol"
+          " table's contents are located beyond the end of the file\n",
+          filename_.c_str());
+}
+
+void Reader::Reporter::UnsupportedCPUType(cpu_type_t cpu_type) {
+  fprintf(stderr, "%s: CPU type %d is not supported\n",
+          filename_.c_str(), cpu_type);
+}
+
+bool Reader::Read(const uint8_t *buffer,
+                  size_t size,
+                  cpu_type_t expected_cpu_type,
+                  cpu_subtype_t expected_cpu_subtype) {
+  assert(!buffer_.start);
+  buffer_.start = buffer;
+  buffer_.end = buffer + size;
+  ByteCursor cursor(&buffer_, true);
+  uint32_t magic;
+  if (!(cursor >> magic)) {
+    reporter_->HeaderTruncated();
+    return false;
+  }
+
+  if (expected_cpu_type != CPU_TYPE_ANY) {
+    uint32_t expected_magic;
+    // validate that magic matches the expected cpu type
+    switch (expected_cpu_type) {
+      case CPU_TYPE_I386:
+        expected_magic = MH_CIGAM;
+        break;
+      case CPU_TYPE_POWERPC:
+        expected_magic = MH_MAGIC;
+        break;
+      case CPU_TYPE_X86_64:
+        expected_magic = MH_CIGAM_64;
+        break;
+      case CPU_TYPE_POWERPC64:
+        expected_magic = MH_MAGIC_64;
+        break;
+      default:
+        reporter_->UnsupportedCPUType(expected_cpu_type);
+        return false;
+    }
+
+    if (expected_magic != magic) {
+      reporter_->BadHeader();
+      return false;
+    }
+  }
+
+  // Since the byte cursor is in big-endian mode, a reversed magic number
+  // always indicates a little-endian file, regardless of our own endianness.
+  switch (magic) {
+    case MH_MAGIC:    big_endian_ = true;  bits_64_ = false; break;
+    case MH_CIGAM:    big_endian_ = false; bits_64_ = false; break;
+    case MH_MAGIC_64: big_endian_ = true;  bits_64_ = true;  break;
+    case MH_CIGAM_64: big_endian_ = false; bits_64_ = true;  break;
+    default:
+      reporter_->BadHeader();
+      return false;
+  }
+  cursor.set_big_endian(big_endian_);
+  uint32_t commands_size, reserved;
+  cursor >> cpu_type_ >> cpu_subtype_ >> file_type_ >> load_command_count_
+         >> commands_size >> flags_;
+  if (bits_64_)
+    cursor >> reserved;
+  if (!cursor) {
+    reporter_->HeaderTruncated();
+    return false;
+  }
+
+  if (expected_cpu_type != CPU_TYPE_ANY &&
+      (expected_cpu_type != cpu_type_ ||
+       expected_cpu_subtype != cpu_subtype_)) {
+    reporter_->CPUTypeMismatch(cpu_type_, cpu_subtype_,
+                              expected_cpu_type, expected_cpu_subtype);
+    return false;
+  }
+
+  cursor
+      .PointTo(&load_commands_.start, commands_size)
+      .PointTo(&load_commands_.end, 0);
+  if (!cursor) {
+    reporter_->LoadCommandRegionTruncated();
+    return false;
+  }
+
+  return true;
+}
+
+bool Reader::WalkLoadCommands(Reader::LoadCommandHandler *handler) const {
+  ByteCursor list_cursor(&load_commands_, big_endian_);
+
+  for (size_t index = 0; index < load_command_count_; ++index) {
+    // command refers to this load command alone, so that cursor will
+    // refuse to read past the load command's end. But since we haven't
+    // read the size yet, let command initially refer to the entire
+    // remainder of the load command series.
+    ByteBuffer command(list_cursor.here(), list_cursor.Available());
+    ByteCursor cursor(&command, big_endian_);
+    
+    // Read the command type and size --- fields common to all commands.
+    uint32_t type, size;
+    if (!(cursor >> type)) {
+      reporter_->LoadCommandsOverrun(load_command_count_, index, 0);
+      return false;
+    }
+    if (!(cursor >> size) || size > command.Size()) {
+      reporter_->LoadCommandsOverrun(load_command_count_, index, type);
+      return false;
+    }
+
+    // Now that we've read the length, restrict command's range to this
+    // load command only.
+    command.end = command.start + size;
+
+    switch (type) {
+      case LC_SEGMENT:
+      case LC_SEGMENT_64: {
+        Segment segment;
+        segment.bits_64 = (type == LC_SEGMENT_64);
+        size_t word_size = segment.bits_64 ? 8 : 4;
+        cursor.CString(&segment.name, 16);
+        size_t file_offset, file_size;
+        cursor
+            .Read(word_size, false, &segment.vmaddr)
+            .Read(word_size, false, &segment.vmsize)
+            .Read(word_size, false, &file_offset)
+            .Read(word_size, false, &file_size);
+        cursor >> segment.maxprot
+               >> segment.initprot
+               >> segment.nsects
+               >> segment.flags;
+        if (!cursor) {
+          reporter_->LoadCommandTooShort(index, type);
+          return false;
+        }
+        if (file_offset > buffer_.Size() ||
+            file_size > buffer_.Size() - file_offset) {
+          reporter_->MisplacedSegmentData(segment.name);
+          return false;
+        }
+        // Mach-O files in .dSYM bundles have the contents of the loaded
+        // segments removed, and their file offsets and file sizes zeroed
+        // out. To help us handle this special case properly, give such
+        // segments' contents NULL starting and ending pointers.
+        if (file_offset == 0 && file_size == 0) {
+          segment.contents.start = segment.contents.end = NULL;
+        } else {
+          segment.contents.start = buffer_.start + file_offset;
+          segment.contents.end = segment.contents.start + file_size;
+        }
+        // The section list occupies the remainder of this load command's space.
+        segment.section_list.start = cursor.here();
+        segment.section_list.end = command.end;
+
+        if (!handler->SegmentCommand(segment))
+          return false;
+        break;
+      }
+
+      case LC_SYMTAB: {
+        uint32_t symoff, nsyms, stroff, strsize;
+        cursor >> symoff >> nsyms >> stroff >> strsize;
+        if (!cursor) {
+          reporter_->LoadCommandTooShort(index, type);
+          return false;
+        }
+        // How big are the entries in the symbol table?
+        // sizeof(struct nlist_64) : sizeof(struct nlist),
+        // but be paranoid about alignment vs. target architecture.
+        size_t symbol_size = bits_64_ ? 16 : 12;
+        // How big is the entire symbol array?
+        size_t symbols_size = nsyms * symbol_size;
+        if (symoff > buffer_.Size() || symbols_size > buffer_.Size() - symoff ||
+            stroff > buffer_.Size() || strsize > buffer_.Size() - stroff) {
+          reporter_->MisplacedSymbolTable();
+          return false;
+        }
+        ByteBuffer entries(buffer_.start + symoff, symbols_size);
+        ByteBuffer names(buffer_.start + stroff, strsize);
+        if (!handler->SymtabCommand(entries, names))
+          return false;
+        break;
+      }
+      
+      default: {
+        if (!handler->UnknownCommand(type, command))
+          return false;
+        break;
+      }
+    }
+
+    list_cursor.set_here(command.end);
+  }
+
+  return true;
+}
+
+// A load command handler that looks for a segment of a given name.
+class Reader::SegmentFinder : public LoadCommandHandler {
+ public:
+  // Create a load command handler that looks for a segment named NAME,
+  // and sets SEGMENT to describe it if found.
+  SegmentFinder(const string &name, Segment *segment) 
+      : name_(name), segment_(segment), found_() { }
+
+  // Return true if the traversal found the segment, false otherwise.
+  bool found() const { return found_; }
+
+  bool SegmentCommand(const Segment &segment) {
+    if (segment.name == name_) {
+      *segment_ = segment;
+      found_ = true;
+      return false;
+    }
+    return true;
+  }
+
+ private:
+  // The name of the segment our creator is looking for.
+  const string &name_;
+
+  // Where we should store the segment if found. (WEAK)
+  Segment *segment_;
+
+  // True if we found the segment.
+  bool found_;
+};
+
+bool Reader::FindSegment(const string &name, Segment *segment) const {
+  SegmentFinder finder(name, segment);
+  WalkLoadCommands(&finder);
+  return finder.found();
+}
+
+bool Reader::WalkSegmentSections(const Segment &segment,
+                                 SectionHandler *handler) const {
+  size_t word_size = segment.bits_64 ? 8 : 4;
+  ByteCursor cursor(&segment.section_list, big_endian_);
+
+  for (size_t i = 0; i < segment.nsects; i++) {
+    Section section;
+    section.bits_64 = segment.bits_64;
+    uint64_t size;
+    uint32_t offset, dummy32;
+    cursor
+        .CString(&section.section_name, 16)
+        .CString(&section.segment_name, 16)
+        .Read(word_size, false, &section.address)
+        .Read(word_size, false, &size)
+        >> offset
+        >> section.align
+        >> dummy32
+        >> dummy32
+        >> section.flags
+        >> dummy32
+        >> dummy32;
+    if (section.bits_64)
+      cursor >> dummy32;
+    if (!cursor) {
+      reporter_->SectionsMissing(segment.name);
+      return false;
+    }
+    if ((section.flags & SECTION_TYPE) == S_ZEROFILL) {
+      // Zero-fill sections have a size, but no contents.
+      section.contents.start = section.contents.end = NULL;
+    } else if (segment.contents.start == NULL && 
+               segment.contents.end == NULL) {
+      // Mach-O files in .dSYM bundles have the contents of the loaded
+      // segments removed, and their file offsets and file sizes zeroed
+      // out.  However, the sections within those segments still have
+      // non-zero sizes.  There's no reason to call MisplacedSectionData in
+      // this case; the caller may just need the section's load
+      // address. But do set the contents' limits to NULL, for safety.
+      section.contents.start = section.contents.end = NULL;
+    } else {
+      if (offset < size_t(segment.contents.start - buffer_.start) ||
+          offset > size_t(segment.contents.end - buffer_.start) ||
+          size > size_t(segment.contents.end - buffer_.start - offset)) {
+        reporter_->MisplacedSectionData(section.section_name,
+                                        section.segment_name);
+        return false;
+      }
+      section.contents.start = buffer_.start + offset;
+      section.contents.end = section.contents.start + size;
+    }
+    if (!handler->HandleSection(section))
+      return false;
+  }
+  return true;
+}
+
+// A SectionHandler that builds a SectionMap for the sections within a
+// given segment.
+class Reader::SectionMapper: public SectionHandler {
+ public:
+  // Create a SectionHandler that populates MAP with an entry for
+  // each section it is given.
+  SectionMapper(SectionMap *map) : map_(map) { }
+  bool HandleSection(const Section &section) {
+    (*map_)[section.section_name] = section;
+    return true;
+  }
+ private:
+  // The map under construction. (WEAK)
+  SectionMap *map_;
+};
+
+bool Reader::MapSegmentSections(const Segment &segment,
+                                SectionMap *section_map) const {
+  section_map->clear();
+  SectionMapper mapper(section_map);
+  return WalkSegmentSections(segment, &mapper);
+}
+
+}  // namespace mach_o
+}  // namespace google_breakpad
diff --git a/src/common/mac/macho_reader.h b/src/common/mac/macho_reader.h
new file mode 100644
index 00000000..75376482
--- /dev/null
+++ b/src/common/mac/macho_reader.h
@@ -0,0 +1,459 @@
+// -*- mode: C++ -*-
+
+// Copyright (c) 2010, 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.
+
+// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// macho_reader.h: A class for parsing Mach-O files.
+
+#ifndef BREAKPAD_COMMON_MAC_MACHO_READER_H_
+#define BREAKPAD_COMMON_MAC_MACHO_READER_H_
+
+#include <mach-o/loader.h>
+#include <mach-o/fat.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "common/byte_cursor.h"
+
+namespace google_breakpad {
+namespace mach_o {
+
+using std::map;
+using std::string;
+using std::vector;
+
+// The Mac headers don't specify particular types for these groups of
+// constants, but defining them here provides some documentation
+// value.  We also give them the same width as the fields in which
+// they appear, which makes them a bit easier to use with ByteCursors.
+typedef uint32_t Magic;
+typedef uint32_t FileType;
+typedef uint32_t FileFlags;
+typedef uint32_t LoadCommandType;
+typedef uint32_t SegmentFlags;
+typedef uint32_t SectionFlags;
+
+// A parser for fat binary files, used to store universal binaries.
+// When applied to a (non-fat) Mach-O file, this behaves as if the
+// file were a fat file containing a single object file.
+class FatReader {
+ public:
+
+  // A class for reporting errors found while parsing fat binary files. The
+  // default definitions of these methods print messages to stderr.
+  class Reporter {
+   public:
+    // Create a reporter that attributes problems to |filename|.
+    explicit Reporter(const string &filename) : filename_(filename) { }
+
+    virtual ~Reporter() { }
+
+    // The data does not begin with a fat binary or Mach-O magic number.
+    // This is a fatal error.
+    virtual void BadHeader();
+
+    // The Mach-O fat binary file ends abruptly, without enough space
+    // to contain an object file it claims is present.
+    virtual void MisplacedObjectFile();
+
+    // The file ends abruptly: either it is not large enough to hold a
+    // complete header, or the header implies that contents are present
+    // beyond the actual end of the file.
+    virtual void TooShort();
+  
+   private:
+    // The filename to which the reader should attribute problems.
+    string filename_;
+  };
+
+  // Create a fat binary file reader that uses |reporter| to report problems.
+  explicit FatReader(Reporter *reporter) : reporter_(reporter) { }
+  
+  // Read the |size| bytes at |buffer| as a fat binary file. On success,
+  // return true; on failure, report the problem to reporter_ and return
+  // false.
+  //
+  // If the data is a plain Mach-O file, rather than a fat binary file,
+  // then the reader behaves as if it had found a fat binary file whose
+  // single object file is the Mach-O file.
+  bool Read(const uint8_t *buffer, size_t size);
+
+  // Return an array of 'struct fat_arch' structures describing the
+  // object files present in this fat binary file. Set |size| to the
+  // number of elements in the array.
+  //
+  // Assuming Read returned true, the entries are validated: it is
+  // safe to assume that the offsets and sizes in each 'struct
+  // fat_arch' refer to subranges of the bytes passed to Read.
+  //
+  // If there are no object files in this fat binary, then this
+  // function can return NULL.
+  //
+  // The array is owned by this FatReader instance; it will be freed when
+  // this FatReader is destroyed.
+  //
+  // This function returns a C-style array instead of a vector to make it
+  // possible to use the result with OS X functions like NXFindBestFatArch,
+  // so that the symbol dumper will behave consistently with other OS X
+  // utilities that work with fat binaries.
+  const struct fat_arch *object_files(size_t *count) const { 
+    *count = object_files_.size();
+    if (object_files_.size() > 0)
+      return &object_files_[0];
+    return NULL;
+  }
+
+ private:
+  // We use this to report problems parsing the file's contents. (WEAK)
+  Reporter *reporter_;
+
+  // The contents of the fat binary or Mach-O file we're parsing. We do not
+  // own the storage it refers to.
+  ByteBuffer buffer_;
+
+  // The magic number of this binary, in host byte order.
+  Magic magic_;
+
+  // The list of object files in this binary.
+  // object_files_.size() == fat_header.nfat_arch
+  vector<struct fat_arch> object_files_;
+};
+
+// A segment in a Mach-O file. All these fields have been byte-swapped as
+// appropriate for use by the executing architecture.
+struct Segment {
+  // The ByteBuffers below point into the bytes passed to the Reader that
+  // created this Segment.
+
+  ByteBuffer section_list;    // This segment's section list.
+  ByteBuffer contents;        // This segment's contents.
+
+  // This segment's name.
+  string name;
+
+  // The address at which this segment should be loaded in memory. If
+  // bits_64 is false, only the bottom 32 bits of this value are valid.
+  uint64_t vmaddr;
+
+  // The size of this segment when loaded into memory. This may be larger
+  // than contents.Size(), in which case the extra area will be
+  // initialized with zeros. If bits_64 is false, only the bottom 32 bits
+  // of this value are valid.
+  uint64_t vmsize;
+
+  // The maximum and initial VM protection of this segment's contents.
+  uint32_t maxprot;
+  uint32_t initprot;
+  
+  // The number of sections in section_list.
+  uint32_t nsects;
+
+  // Flags describing this segment, from SegmentFlags.
+  uint32_t flags;
+
+  // True if this is a 64-bit section; false if it is a 32-bit section.
+  bool bits_64;
+};
+
+// A section in a Mach-O file. All these fields have been byte-swapped as
+// appropriate for use by the executing architecture.
+struct Section {
+  // This section's contents. This points into the bytes passed to the
+  // Reader that created this Section.
+  ByteBuffer contents;
+
+  // This section's name.
+  string section_name;  // section[_64].sectname
+  // The name of the segment this section belongs to.
+  string segment_name;  // section[_64].segname
+
+  // The address at which this section's contents should be loaded in
+  // memory. If bits_64 is false, only the bottom 32 bits of this value
+  // are valid.
+  uint64_t address;
+
+  // The contents of this section should be loaded into memory at an
+  // address which is a multiple of (two raised to this power).
+  uint32_t align;
+
+  // Flags from SectionFlags describing the section's contents.
+  uint32_t flags;
+
+  // We don't support reading relocations yet.
+
+  // True if this is a 64-bit section; false if it is a 32-bit section.
+  bool bits_64;
+};
+
+// A map from section names to Sections.
+typedef map<string, Section> SectionMap;
+
+// A reader for a Mach-O file.
+//
+// This does not handle fat binaries; see FatReader above. FatReader
+// provides a friendly interface for parsing data that could be either a
+// fat binary or a Mach-O file.
+class Reader {
+ public:
+
+  // A class for reporting errors found while parsing Mach-O files. The
+  // default definitions of these member functions print messages to
+  // stderr.
+  class Reporter {
+   public:
+    // Create a reporter that attributes problems to |filename|.
+    explicit Reporter(const string &filename) : filename_(filename) { }
+    virtual ~Reporter() { }
+
+    // Reporter functions for fatal errors return void; the reader will
+    // definitely return an error to its caller after calling them
+
+    // The data does not begin with a Mach-O magic number, or the magic
+    // number does not match the expected value for the cpu architecture.
+    // This is a fatal error.
+    virtual void BadHeader();
+
+    // The data contained in a Mach-O fat binary (|cpu_type|, |cpu_subtype|)
+    // does not match the expected CPU architecture
+    // (|expected_cpu_type|, |expected_cpu_subtype|).
+    virtual void CPUTypeMismatch(cpu_type_t cpu_type,
+                                 cpu_subtype_t cpu_subtype,
+                                 cpu_type_t expected_cpu_type,
+                                 cpu_subtype_t expected_cpu_subtype);
+
+    // The file ends abruptly: either it is not large enough to hold a
+    // complete header, or the header implies that contents are present
+    // beyond the actual end of the file.
+    virtual void HeaderTruncated();
+
+    // The file's load command region, as given in the Mach-O header, is
+    // too large for the file.
+    virtual void LoadCommandRegionTruncated();
+
+    // The file's Mach-O header claims the file contains |claimed| load
+    // commands, but the I'th load command, of type |type|, extends beyond
+    // the end of the load command region, as given by the Mach-O header.
+    // If |type| is zero, the command's type was unreadable.
+    virtual void LoadCommandsOverrun(size_t claimed, size_t i,
+                                     LoadCommandType type);
+
+    // The contents of the |i|'th load command, of type |type|, extend beyond
+    // the size given in the load command's header.
+    virtual void LoadCommandTooShort(size_t i, LoadCommandType type);
+
+    // The LC_SEGMENT or LC_SEGMENT_64 load command for the segment named
+    // |name| is too short to hold the sections that its header says it does.
+    // (This more specific than LoadCommandTooShort.)
+    virtual void SectionsMissing(const string &name);
+
+    // The segment named |name| claims that its contents lie beyond the end
+    // of the file.
+    virtual void MisplacedSegmentData(const string &name);
+
+    // The section named |section| in the segment named |segment| claims that
+    // its contents do not lie entirely within the segment.
+    virtual void MisplacedSectionData(const string &section,
+                                      const string &segment);
+
+    // The LC_SYMTAB command claims that symbol table contents are located
+    // beyond the end of the file.
+    virtual void MisplacedSymbolTable();
+
+    // An attempt was made to read a Mach-O file of the unsupported
+    // CPU architecture |cpu_type|.
+    virtual void UnsupportedCPUType(cpu_type_t cpu_type);
+
+   private:
+    string filename_;
+  };
+
+  // A handler for sections parsed from a segment. The WalkSegmentSections
+  // member function accepts an instance of this class, and applies it to
+  // each section defined in a given segment.
+  class SectionHandler {
+   public:
+    virtual ~SectionHandler() { }
+
+    // Called to report that the segment's section list contains |section|.
+    // This should return true if the iteration should continue, or false
+    // if it should stop.
+    virtual bool HandleSection(const Section &section) = 0;
+  };
+
+  // A handler for the load commands in a Mach-O file.
+  class LoadCommandHandler {
+   public:
+    LoadCommandHandler() { }
+    virtual ~LoadCommandHandler() { }
+
+    // When called from WalkLoadCommands, the following handler functions
+    // should return true if they wish to continue iterating over the load
+    // command list, or false if they wish to stop iterating.
+    //
+    // When called from LoadCommandIterator::Handle or Reader::Handle,
+    // these functions' return values are simply passed through to Handle's
+    // caller.
+    //
+    // The definitions provided by this base class simply return true; the
+    // default is to silently ignore sections whose member functions the
+    // subclass doesn't override.
+
+    // COMMAND is load command we don't recognize. We provide only the
+    // command type and a ByteBuffer enclosing the command's data (If we
+    // cannot parse the command type or its size, we call
+    // reporter_->IncompleteLoadCommand instead.)
+    virtual bool UnknownCommand(LoadCommandType type,
+                                const ByteBuffer &contents) {
+      return true;
+    }
+
+    // The load command is LC_SEGMENT or LC_SEGMENT_64, defining a segment
+    // with the properties given in |segment|.
+    virtual bool SegmentCommand(const Segment &segment) {
+      return true;
+    }
+
+    // The load command is LC_SYMTAB. |entries| holds the array of nlist
+    // entries, and |names| holds the strings the entries refer to.
+    virtual bool SymtabCommand(const ByteBuffer &entries,
+                               const ByteBuffer &names) {
+      return true;
+    }
+
+    // Add handler functions for more load commands here as needed.
+  };
+
+  // Create a Mach-O file reader that reports problems to |reporter|.
+  explicit Reader(Reporter *reporter)
+      : reporter_(reporter) { }
+
+  // Read the given data as a Mach-O file. The reader retains pointers
+  // into the data passed, so the data should live as long as the reader
+  // does. On success, return true; on failure, return false.
+  //
+  // At most one of these functions should be invoked once on each Reader
+  // instance.
+  bool Read(const uint8_t *buffer,
+            size_t size,
+            cpu_type_t expected_cpu_type,
+            cpu_subtype_t expected_cpu_subtype);
+  bool Read(const ByteBuffer &buffer,
+            cpu_type_t expected_cpu_type,
+            cpu_subtype_t expected_cpu_subtype) {
+    return Read(buffer.start,
+                buffer.Size(),
+                expected_cpu_type,
+                expected_cpu_subtype); 
+  }
+
+  // Return this file's characteristics, as found in the Mach-O header.
+  cpu_type_t    cpu_type()    const { return cpu_type_; }
+  cpu_subtype_t cpu_subtype() const { return cpu_subtype_; }
+  FileType      file_type()   const { return file_type_; }
+  FileFlags     flags()       const { return flags_; }
+
+  // Return true if this is a 64-bit Mach-O file, false if it is a 32-bit
+  // Mach-O file.
+  bool bits_64() const { return bits_64_; }
+
+  // Return true if this is a big-endian Mach-O file, false if it is
+  // little-endian.
+  bool big_endian() const { return big_endian_; }
+
+  // Apply |handler| to each load command in this Mach-O file, stopping when
+  // a handler function returns false. If we encounter a malformed load
+  // command, report it via reporter_ and return false. Return true if all
+  // load commands were parseable and all handlers returned true.
+  bool WalkLoadCommands(LoadCommandHandler *handler) const;
+
+  // Set |segment| to describe the segment named |name|, if present. If
+  // found, |segment|'s byte buffers refer to a subregion of the bytes
+  // passed to Read. If we find the section, return true; otherwise,
+  // return false.
+  bool FindSegment(const string &name, Segment *segment) const;
+
+  // Apply |handler| to each section defined in |segment|. If |handler| returns
+  // false, stop iterating and return false. If all calls to |handler| return
+  // true and we reach the end of the section list, return true.
+  bool WalkSegmentSections(const Segment &segment, SectionHandler *handler)
+    const;
+
+  // Clear |section_map| and then populate it with a map of the sections
+  // in |segment|, from section names to Section structures.
+  // Each Section's contents refer to bytes in |segment|'s contents.
+  // On success, return true; if a problem occurs, report it and return false.
+  bool MapSegmentSections(const Segment &segment, SectionMap *section_map)
+    const;
+
+ private:
+  // Used internally.
+  class SegmentFinder;
+  class SectionMapper;
+
+  // We use this to report problems parsing the file's contents. (WEAK)
+  Reporter *reporter_;
+
+  // The contents of the Mach-O file we're parsing. We do not own the
+  // storage it refers to.
+  ByteBuffer buffer_;
+
+  // True if this file is big-endian.
+  bool big_endian_;
+
+  // True if this file is a 64-bit Mach-O file.
+  bool bits_64_;
+
+  // This file's cpu type and subtype.
+  cpu_type_t cpu_type_;        // mach_header[_64].cputype
+  cpu_subtype_t cpu_subtype_;  // mach_header[_64].cpusubtype
+
+  // This file's type.
+  FileType file_type_;         // mach_header[_64].filetype
+
+  // The region of buffer_ occupied by load commands.
+  ByteBuffer load_commands_;
+
+  // The number of load commands in load_commands_.
+  uint32_t load_command_count_;  // mach_header[_64].ncmds
+
+  // This file's header flags.
+  FileFlags flags_;
+};
+
+}  // namespace mach_o
+}  // namespace google_breakpad
+
+#endif  // BREAKPAD_COMMON_MAC_MACHO_READER_H_
diff --git a/src/common/mac/macho_reader_unittest.cc b/src/common/mac/macho_reader_unittest.cc
new file mode 100644
index 00000000..4e478d79
--- /dev/null
+++ b/src/common/mac/macho_reader_unittest.cc
@@ -0,0 +1,1898 @@
+// Copyright (c) 2010 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.
+
+// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+
+// macho_reader_unittest.cc: Unit tests for google_breakpad::Mach_O::FatReader
+// and google_breakpad::Mach_O::Reader.
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "breakpad_googletest_includes.h"
+#include "common/mac/macho_reader.h"
+#include "common/test_assembler.h"
+
+namespace mach_o = google_breakpad::mach_o;
+namespace test_assembler = google_breakpad::test_assembler;
+
+using mach_o::FatReader;
+using mach_o::FileFlags;
+using mach_o::FileType;
+using mach_o::LoadCommandType;
+using mach_o::Reader;
+using mach_o::Section;
+using mach_o::SectionMap;
+using mach_o::Segment;
+using test_assembler::Endianness;
+using test_assembler::Label;
+using test_assembler::kBigEndian;
+using test_assembler::kLittleEndian;
+using test_assembler::kUnsetEndian;
+using google_breakpad::ByteBuffer;
+using std::map;
+using std::string;
+using std::vector;
+using testing::AllOf;
+using testing::DoAll;
+using testing::Field;
+using testing::InSequence;
+using testing::Matcher;
+using testing::Return;
+using testing::SaveArg;
+using testing::Test;
+using testing::_;
+
+
+// Mock classes for the reader's various reporters and handlers.
+
+class MockFatReaderReporter: public FatReader::Reporter {
+ public:
+  MockFatReaderReporter(const string &filename)
+      : FatReader::Reporter(filename) { }
+  MOCK_METHOD0(BadHeader, void());
+  MOCK_METHOD0(MisplacedObjectFile, void());
+  MOCK_METHOD0(TooShort, void());
+};
+
+class MockReaderReporter: public Reader::Reporter {
+ public:
+  MockReaderReporter(const string &filename) : Reader::Reporter(filename) { }
+  MOCK_METHOD0(BadHeader, void());
+  MOCK_METHOD4(CPUTypeMismatch, void(cpu_type_t cpu_type,
+                                     cpu_subtype_t cpu_subtype,
+                                     cpu_type_t expected_cpu_type,
+                                     cpu_subtype_t expected_cpu_subtype));
+  MOCK_METHOD0(HeaderTruncated, void());
+  MOCK_METHOD0(LoadCommandRegionTruncated, void());
+  MOCK_METHOD3(LoadCommandsOverrun, void(size_t claimed, size_t i,
+                                         LoadCommandType type));
+  MOCK_METHOD2(LoadCommandTooShort, void(size_t i, LoadCommandType type));
+  MOCK_METHOD1(SectionsMissing, void(const string &name));
+  MOCK_METHOD1(MisplacedSegmentData, void(const string &name));
+  MOCK_METHOD2(MisplacedSectionData, void(const string &section,
+                                          const string &segment));
+  MOCK_METHOD0(MisplacedSymbolTable, void());
+  MOCK_METHOD1(UnsupportedCPUType, void(cpu_type_t cpu_type));
+};
+
+class MockLoadCommandHandler: public Reader::LoadCommandHandler {
+ public:
+  MOCK_METHOD2(UnknownCommand, bool(LoadCommandType, const ByteBuffer &));
+  MOCK_METHOD1(SegmentCommand, bool(const Segment &));
+  MOCK_METHOD2(SymtabCommand,  bool(const ByteBuffer &, const ByteBuffer &));
+};
+
+class MockSectionHandler: public Reader::SectionHandler {
+ public:
+  MOCK_METHOD1(HandleSection, bool(const Section &section));
+};
+
+
+// Tests for mach_o::FatReader.
+
+// Since the effect of these functions is to write to stderr, the
+// results of these tests must be inspected by hand.
+TEST(FatReaderReporter, BadHeader) {
+  FatReader::Reporter reporter("filename");
+  reporter.BadHeader();
+}
+
+TEST(FatReaderReporter, MisplacedObjectFile) {
+  FatReader::Reporter reporter("filename");
+  reporter.MisplacedObjectFile();
+}
+
+TEST(FatReaderReporter, TooShort) {
+  FatReader::Reporter reporter("filename");
+  reporter.TooShort();
+}
+
+TEST(MachOReaderReporter, BadHeader) {
+  Reader::Reporter reporter("filename");
+  reporter.BadHeader();
+}
+
+TEST(MachOReaderReporter, CPUTypeMismatch) {
+  Reader::Reporter reporter("filename");
+  reporter.CPUTypeMismatch(CPU_TYPE_I386, CPU_SUBTYPE_X86_ALL,
+                           CPU_TYPE_POWERPC, CPU_SUBTYPE_POWERPC_ALL);
+}
+
+TEST(MachOReaderReporter, HeaderTruncated) {
+  Reader::Reporter reporter("filename");
+  reporter.HeaderTruncated();
+}
+
+TEST(MachOReaderReporter, LoadCommandRegionTruncated) {
+  Reader::Reporter reporter("filename");
+  reporter.LoadCommandRegionTruncated();
+}
+
+TEST(MachOReaderReporter, LoadCommandsOverrun) {
+  Reader::Reporter reporter("filename");
+  reporter.LoadCommandsOverrun(10, 9, LC_DYSYMTAB);
+  reporter.LoadCommandsOverrun(10, 9, 0);
+}
+
+TEST(MachOReaderReporter, LoadCommandTooShort) {
+  Reader::Reporter reporter("filename");
+  reporter.LoadCommandTooShort(11, LC_SYMTAB);
+}
+
+TEST(MachOReaderReporter, SectionsMissing) {
+  Reader::Reporter reporter("filename");
+  reporter.SectionsMissing("segment name");
+}
+
+TEST(MachOReaderReporter, MisplacedSegmentData) {
+  Reader::Reporter reporter("filename");
+  reporter.MisplacedSegmentData("segment name");
+}
+
+TEST(MachOReaderReporter, MisplacedSectionData) {
+  Reader::Reporter reporter("filename");
+  reporter.MisplacedSectionData("section name", "segment name");
+}
+
+TEST(MachOReaderReporter, MisplacedSymbolTable) {
+  Reader::Reporter reporter("filename");
+  reporter.MisplacedSymbolTable();
+}
+
+TEST(MachOReaderReporter, UnsupportedCPUType) {
+  Reader::Reporter reporter("filename");
+  reporter.UnsupportedCPUType(CPU_TYPE_HPPA);
+}
+
+struct FatReaderFixture {
+  FatReaderFixture()
+      : fat(kBigEndian),
+        reporter("reporter filename"),
+        reader(&reporter), object_files(), object_files_size() { 
+    EXPECT_CALL(reporter, BadHeader()).Times(0);
+    EXPECT_CALL(reporter, TooShort()).Times(0);
+
+    // here, start, and Mark are file offsets in 'fat'.
+    fat.start() = 0;
+  }
+  // Append a 'fat_arch' entry to 'fat', with the given field values.
+  void AppendFatArch(cpu_type_t type, cpu_subtype_t subtype,
+                     Label offset, Label size, uint32_t align) {
+    fat
+        .B32(type)
+        .B32(subtype)
+        .B32(offset)
+        .B32(size)
+        .B32(align);
+  }
+  // Append |n| dummy 'fat_arch' entries to 'fat'. The cpu type and
+  // subtype have unrealistic values.
+  void AppendDummyArchEntries(int n) {
+    for (int i = 0; i < n; i++)
+      AppendFatArch(0xb68ad617, 0x715a0840, 0, 0, 1);
+  }
+  void ReadFat(bool expect_parse_success = true) {
+    ASSERT_TRUE(fat.GetContents(&contents));
+    fat_bytes = reinterpret_cast<const uint8_t *>(contents.data());
+    if (expect_parse_success) {
+      EXPECT_TRUE(reader.Read(fat_bytes, contents.size()));
+      object_files = reader.object_files(&object_files_size);
+    }
+    else
+      EXPECT_FALSE(reader.Read(fat_bytes, contents.size()));
+  }
+  test_assembler::Section fat;
+  MockFatReaderReporter reporter;
+  FatReader reader;
+  string contents;
+  const uint8_t *fat_bytes;
+  const struct fat_arch *object_files;
+  size_t object_files_size;
+};
+
+class FatReaderTest: public FatReaderFixture, public Test { };
+
+TEST_F(FatReaderTest, BadMagic) {
+  EXPECT_CALL(reporter, BadHeader()).Times(1);
+  fat
+      .B32(0xcafed00d)           // magic number (incorrect)
+      .B32(10);                  // number of architectures
+  AppendDummyArchEntries(10);
+  ReadFat(false);
+}
+
+TEST_F(FatReaderTest, HeaderTooShort) {
+  EXPECT_CALL(reporter, TooShort()).Times(1);
+  fat
+      .B32(0xcafebabe);             // magic number
+  ReadFat(false);
+}
+
+TEST_F(FatReaderTest, ObjectListTooShort) {
+  EXPECT_CALL(reporter, TooShort()).Times(1);
+  fat
+      .B32(0xcafebabe)              // magic number
+      .B32(10);                     // number of architectures
+  AppendDummyArchEntries(9);        // nine dummy architecture entries...
+  fat                               // and a tenth, missing a byte at the end
+      .B32(0x3d46c8fc)              // cpu type
+      .B32(0x8a7bfb01)              // cpu subtype
+      .B32(0)                       // offset
+      .B32(0)                       // size
+      .Append(3, '*');              // one byte short of a four-byte alignment
+  ReadFat(false);
+}
+
+TEST_F(FatReaderTest, DataTooShort) {
+  EXPECT_CALL(reporter, MisplacedObjectFile()).Times(1);
+  Label arch_data;
+  fat
+      .B32(0xcafebabe)              // magic number
+      .B32(1);                      // number of architectures
+  AppendFatArch(0xb4d4a366, 0x4ba4f525, arch_data, 40, 0);
+  fat
+      .Mark(&arch_data)             // file data begins here
+      .Append(30, '*');             // only 30 bytes, not 40 as header claims
+  ReadFat(false);
+}
+
+TEST_F(FatReaderTest, NoObjectFiles) {
+  fat
+      .B32(0xcafebabe)              // magic number
+      .B32(0);                      // number of architectures
+  ReadFat();
+  EXPECT_EQ(0U, object_files_size);
+}
+
+TEST_F(FatReaderTest, OneObjectFile) {
+  Label obj1_offset;
+  fat
+      .B32(0xcafebabe)              // magic number
+      .B32(1);                      // number of architectures
+  // First object file list entry
+  AppendFatArch(0x5e3a6e91, 0x52ccd852, obj1_offset, 0x42, 0x355b15b2);
+  // First object file data
+  fat
+      .Mark(&obj1_offset)           
+      .Append(0x42, '*');           // dummy contents
+  ReadFat();
+  ASSERT_EQ(1U, object_files_size);
+  EXPECT_EQ(0x5e3a6e91, object_files[0].cputype);
+  EXPECT_EQ(0x52ccd852, object_files[0].cpusubtype);
+  EXPECT_EQ(obj1_offset.Value(), object_files[0].offset);
+  EXPECT_EQ(0x42U, object_files[0].size);
+  EXPECT_EQ(0x355b15b2U, object_files[0].align);
+}
+
+TEST_F(FatReaderTest, ThreeObjectFiles) {
+  Label obj1, obj2, obj3;
+  fat
+      .B32(0xcafebabe)              // magic number
+      .B32(3);                      // number of architectures
+  // Three object file list entries.
+  AppendFatArch(0x0cb92c30, 0x6a159a71, obj1, 0xfb4, 0x2615dbe8);
+  AppendFatArch(0x0f3f1cbb, 0x6c55e90f, obj2, 0xc31, 0x83af6ffd);
+  AppendFatArch(0x3717276d, 0x10ecdc84, obj3, 0x4b3, 0x035267d7);
+  fat
+      // First object file data
+      .Mark(&obj1)           
+      .Append(0xfb4, '*')           // dummy contents
+      // Second object file data
+      .Mark(&obj2)           
+      .Append(0xc31, '%')           // dummy contents
+      // Third object file data
+      .Mark(&obj3)           
+      .Append(0x4b3, '^');          // dummy contents
+  
+  ReadFat();
+
+  ASSERT_EQ(3U, object_files_size);
+
+  // First object file.
+  EXPECT_EQ(0x0cb92c30, object_files[0].cputype);
+  EXPECT_EQ(0x6a159a71, object_files[0].cpusubtype);
+  EXPECT_EQ(obj1.Value(), object_files[0].offset);
+  EXPECT_EQ(0xfb4U, object_files[0].size);
+  EXPECT_EQ(0x2615dbe8U, object_files[0].align);
+
+  // Second object file.
+  EXPECT_EQ(0x0f3f1cbb, object_files[1].cputype);
+  EXPECT_EQ(0x6c55e90f, object_files[1].cpusubtype);
+  EXPECT_EQ(obj2.Value(), object_files[1].offset);
+  EXPECT_EQ(0xc31U, object_files[1].size);
+  EXPECT_EQ(0x83af6ffdU, object_files[1].align);
+
+  // Third object file.
+  EXPECT_EQ(0x3717276d, object_files[2].cputype);
+  EXPECT_EQ(0x10ecdc84, object_files[2].cpusubtype);
+  EXPECT_EQ(obj3.Value(), object_files[2].offset);
+  EXPECT_EQ(0x4b3U, object_files[2].size);
+  EXPECT_EQ(0x035267d7U, object_files[2].align);
+}
+
+TEST_F(FatReaderTest, BigEndianMachO32) {
+  fat.set_endianness(kBigEndian);
+  fat
+      .D32(0xfeedface)                  // Mach-O file magic number
+      .D32(0x1a9d0518)                  // cpu type
+      .D32(0x1b779357)                  // cpu subtype
+      .D32(0x009df67e)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // the load commands occupy no bytes
+      .D32(0x21987a99);                 // flags
+
+  ReadFat();
+
+  // FatReader should treat a Mach-O file as if it were a fat binary file
+  // containing one object file --- the whole thing.
+  ASSERT_EQ(1U, object_files_size);
+  EXPECT_EQ(0x1a9d0518, object_files[0].cputype);
+  EXPECT_EQ(0x1b779357, object_files[0].cpusubtype);
+  EXPECT_EQ(0U, object_files[0].offset);
+  EXPECT_EQ(contents.size(), object_files[0].size);
+}
+
+TEST_F(FatReaderTest, BigEndianMachO64) {
+  fat.set_endianness(kBigEndian);
+  fat
+      .D32(0xfeedfacf)                  // Mach-O 64-bit file magic number
+      .D32(0x5aff8487)                  // cpu type
+      .D32(0x4c6a57f7)                  // cpu subtype
+      .D32(0x4392d2c8)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // the load commands occupy no bytes
+      .D32(0x1b033eea);                 // flags
+
+  ReadFat();
+
+  // FatReader should treat a Mach-O file as if it were a fat binary file
+  // containing one object file --- the whole thing.
+  ASSERT_EQ(1U, object_files_size);
+  EXPECT_EQ(0x5aff8487, object_files[0].cputype);
+  EXPECT_EQ(0x4c6a57f7, object_files[0].cpusubtype);
+  EXPECT_EQ(0U, object_files[0].offset);
+  EXPECT_EQ(contents.size(), object_files[0].size);
+}
+
+TEST_F(FatReaderTest, LittleEndianMachO32) {
+  fat.set_endianness(kLittleEndian);
+  fat
+      .D32(0xfeedface)                  // Mach-O file magic number
+      .D32(0x1a9d0518)                  // cpu type
+      .D32(0x1b779357)                  // cpu subtype
+      .D32(0x009df67e)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // the load commands occupy no bytes
+      .D32(0x21987a99);                 // flags
+
+  ReadFat();
+
+  // FatReader should treat a Mach-O file as if it were a fat binary file
+  // containing one object file --- the whole thing.
+  ASSERT_EQ(1U, object_files_size);
+  EXPECT_EQ(0x1a9d0518, object_files[0].cputype);
+  EXPECT_EQ(0x1b779357, object_files[0].cpusubtype);
+  EXPECT_EQ(0U, object_files[0].offset);
+  EXPECT_EQ(contents.size(), object_files[0].size);
+}
+
+TEST_F(FatReaderTest, LittleEndianMachO64) {
+  fat.set_endianness(kLittleEndian);
+  fat
+      .D32(0xfeedfacf)                  // Mach-O 64-bit file magic number
+      .D32(0x5aff8487)                  // cpu type
+      .D32(0x4c6a57f7)                  // cpu subtype
+      .D32(0x4392d2c8)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // the load commands occupy no bytes
+      .D32(0x1b033eea);                 // flags
+
+  ReadFat();
+
+  // FatReader should treat a Mach-O file as if it were a fat binary file
+  // containing one object file --- the whole thing.
+  ASSERT_EQ(1U, object_files_size);
+  EXPECT_EQ(0x5aff8487, object_files[0].cputype);
+  EXPECT_EQ(0x4c6a57f7, object_files[0].cpusubtype);
+  EXPECT_EQ(0U, object_files[0].offset);
+  EXPECT_EQ(contents.size(), object_files[0].size);
+}
+
+TEST_F(FatReaderTest, IncompleteMach) {
+  fat.set_endianness(kLittleEndian);
+  fat
+      .D32(0xfeedfacf)                  // Mach-O 64-bit file magic number
+      .D32(0x5aff8487);                 // cpu type
+      // Truncated!
+
+  EXPECT_CALL(reporter, TooShort()).WillOnce(Return());
+
+  ReadFat(false);
+}
+
+
+// General mach_o::Reader tests.
+
+// Dynamically scoped configuration data.
+class WithConfiguration {
+ public:
+  // Establish the given parameters as the default for SizedSections
+  // created within the dynamic scope of this instance.
+  WithConfiguration(Endianness endianness, size_t word_size)
+      : endianness_(endianness), word_size_(word_size), saved_(current_) {
+    current_ = this;
+  }
+  ~WithConfiguration() { current_ = saved_; }
+  static Endianness endianness() { 
+    assert(current_);
+    return current_->endianness_;
+  }
+  static size_t word_size() { 
+    assert(current_);
+    return current_->word_size_;
+  }
+
+ private:
+  // The innermost WithConfiguration in whose dynamic scope we are
+  // currently executing.
+  static WithConfiguration *current_;
+
+  // The innermost WithConfiguration whose dynamic scope encloses this
+  // WithConfiguration.
+  Endianness endianness_;
+  size_t word_size_;
+  WithConfiguration *saved_;
+};
+
+WithConfiguration *WithConfiguration::current_ = NULL;
+
+// A test_assembler::Section with a size that we can cite. The start(),
+// Here() and Mark() member functions of a SizedSection always represent
+// offsets within the overall file.
+class SizedSection: public test_assembler::Section {
+ public:
+  // Construct a section of the given endianness and word size.
+  explicit SizedSection(Endianness endianness, size_t word_size)
+      : test_assembler::Section(endianness), word_size_(word_size) {
+    assert(word_size_ == 32 || word_size_ == 64);
+  }
+  SizedSection()
+      : test_assembler::Section(WithConfiguration::endianness()),
+        word_size_(WithConfiguration::word_size()) {
+    assert(word_size_ == 32 || word_size_ == 64);
+  }
+
+  // Access/set this section's word size.
+  size_t word_size() const { return word_size_; }
+  void set_word_size(size_t word_size) { 
+    assert(word_size_ == 32 || word_size_ == 64);
+    word_size_ = word_size;
+  }
+
+  // Return a label representing the size this section will have when it
+  // is Placed in some containing section.
+  Label final_size() const { return final_size_; }
+
+  // Append SECTION to the end of this section, and call its Finish member.
+  // Return a reference to this section.
+  SizedSection &Place(SizedSection *section) {
+    assert(section->endianness() == endianness());
+    section->Finish();
+    section->start() = Here();
+    test_assembler::Section::Append(*section);
+    return *this;
+  }
+
+ protected:
+  // Mark this section's contents as complete. For plain SizedSections, we
+  // set SECTION's start to its position in this section, and its final_size
+  // label to its current size. Derived classes can extend this as needed
+  // for their additional semantics.
+  virtual void Finish() {
+    final_size_ = Size();
+  }
+
+  // The word size for this data: either 32 or 64.
+  size_t word_size_;
+
+ private:
+  // This section's final size, set when we are placed in some other
+  // SizedSection.
+  Label final_size_;
+};
+
+// A SizedSection that is loaded into memory at a particular address.
+class LoadedSection: public SizedSection {
+ public:
+  explicit LoadedSection(Label address = Label()) : address_(address) { }
+
+  // Return a label representing this section's address.
+  Label address() const { return address_; }
+
+  // Placing a loaded section within a loaded section sets the relationship
+  // between their addresses.
+  LoadedSection &Place(LoadedSection *section) {
+    section->address() = address() + Size();
+    SizedSection::Place(section);
+    return *this;
+  }
+
+ protected:
+  // The address at which this section's contents will be loaded.
+  Label address_;
+};
+  
+// A SizedSection representing a segment load command.
+class SegmentLoadCommand: public SizedSection {
+ public:
+  SegmentLoadCommand() : section_count_(0) { }
+
+  // Append a segment load command header with the given characteristics.
+  // The load command will refer to CONTENTS, which must be Placed in the
+  // file separately, at the desired position. Return a reference to this
+  // section.
+  SegmentLoadCommand &Header(const string &name, const LoadedSection &contents,
+                             uint32_t maxprot, uint32_t initprot,
+                             uint32_t flags) {
+    assert(contents.word_size() == word_size());
+    D32(word_size() == 32 ? LC_SEGMENT : LC_SEGMENT_64);
+    D32(final_size());
+    AppendCString(name, 16);
+    Append(endianness(), word_size() / 8, contents.address());
+    Append(endianness(), word_size() / 8, vmsize_);
+    Append(endianness(), word_size() / 8, contents.start());
+    Append(endianness(), word_size() / 8, contents.final_size());
+    D32(maxprot);
+    D32(initprot);
+    D32(final_section_count_);
+    D32(flags);
+
+    content_final_size_ = contents.final_size();
+
+    return *this;
+  }
+
+  // Return a label representing the size of this segment when loaded into
+  // memory. If this label is still undefined by the time we place this
+  // segment, it defaults to the final size of the segment's in-file
+  // contents. Return a reference to this load command.
+  Label &vmsize() { return vmsize_; }
+
+  // Add a section entry with the given characteristics to this segment
+  // load command. Return a reference to this. The section entry will refer
+  // to CONTENTS, which must be Placed in the segment's contents
+  // separately, at the desired position.
+  SegmentLoadCommand &AppendSectionEntry(const string &section_name,
+                                         const string &segment_name,
+                                         uint32_t alignment, uint32_t flags,
+                                         const LoadedSection &contents) {
+    AppendCString(section_name, 16);
+    AppendCString(segment_name, 16);
+    Append(endianness(), word_size() / 8, contents.address());
+    Append(endianness(), word_size() / 8, contents.final_size());
+    D32(contents.start());
+    D32(alignment);
+    D32(0);                  // relocations start
+    D32(0);                  // relocations size
+    D32(flags);
+    D32(0x93656b95);         // reserved1
+    D32(0xc35a2473);         // reserved2
+    if (word_size() == 64)
+      D32(0x70284b95);       // reserved3
+
+    section_count_++;
+
+    return *this;
+  }
+
+ protected:
+  void Finish() {
+    final_section_count_ = section_count_;
+    if (!vmsize_.IsKnownConstant())
+      vmsize_ = content_final_size_;
+    SizedSection::Finish();
+  }
+
+ private:
+  // The number of sections that have been added to this segment so far.
+  size_t section_count_;
+
+  // A label representing the final number of sections this segment will hold.
+  Label final_section_count_;
+
+  // The size of the contents for this segment present in the file.
+  Label content_final_size_;
+
+  // A label representing the size of this segment when loaded; this can be
+  // larger than the size of its file contents, the difference being
+  // zero-filled. If not set explicitly by calling set_vmsize, this is set
+  // equal to the size of the contents.
+  Label vmsize_;
+};
+
+// A SizedSection holding a list of Mach-O load commands.
+class LoadCommands: public SizedSection {
+ public:
+  LoadCommands() : command_count_(0) { }
+
+  // Return a label representing the final load command count.
+  Label final_command_count() const { return final_command_count_; }
+
+  // Increment the command count; return a reference to this section.
+  LoadCommands &CountCommand() {
+    command_count_++;
+    return *this;
+  }
+
+  // Place COMMAND, containing a load command, at the end of this section.
+  // Return a reference to this section.
+  LoadCommands &Place(SizedSection *section) {
+    SizedSection::Place(section);
+    CountCommand();
+    return *this;
+  }
+
+ protected:
+  // Mark this load command list as complete.
+  void Finish() {
+    SizedSection::Finish();
+    final_command_count_ = command_count_;
+  }
+
+ private:
+  // The number of load commands we have added to this file so far.
+  size_t command_count_;
+
+  // A label representing the final command count.
+  Label final_command_count_;
+};
+
+// A SizedSection holding the contents of a Mach-O file. Within a
+// MachOFile, the start, Here, and Mark members refer to file offsets.
+class MachOFile: public SizedSection {
+ public:
+  MachOFile() { 
+    start() = 0;
+  }
+
+  // Create a Mach-O file header using the given characteristics and load
+  // command list. This Places COMMANDS immediately after the header.
+  // Return a reference to this section.
+  MachOFile &Header(LoadCommands *commands,
+                    cpu_type_t cpu_type = CPU_TYPE_X86,
+                    cpu_subtype_t cpu_subtype = CPU_SUBTYPE_I386_ALL,
+                    FileType file_type = MH_EXECUTE,
+                    uint32_t file_flags = (MH_TWOLEVEL |
+                                           MH_DYLDLINK |
+                                           MH_NOUNDEFS)) {
+    D32(word_size() == 32 ? 0xfeedface : 0xfeedfacf);  // magic number
+    D32(cpu_type);                              // cpu type
+    D32(cpu_subtype);                           // cpu subtype
+    D32(file_type);                             // file type
+    D32(commands->final_command_count());       // number of load commands
+    D32(commands->final_size());                // their size in bytes
+    D32(file_flags);                            // flags
+    if (word_size() == 64)
+      D32(0x55638b90);                          // reserved
+    Place(commands);
+    return *this;
+  }
+};
+
+
+struct ReaderFixture {
+  ReaderFixture()
+      : reporter("reporter filename"),
+        reader(&reporter) { 
+    EXPECT_CALL(reporter, BadHeader()).Times(0);
+    EXPECT_CALL(reporter, CPUTypeMismatch(_, _, _, _)).Times(0);
+    EXPECT_CALL(reporter, HeaderTruncated()).Times(0);
+    EXPECT_CALL(reporter, LoadCommandRegionTruncated()).Times(0);
+    EXPECT_CALL(reporter, LoadCommandsOverrun(_, _, _)).Times(0);
+    EXPECT_CALL(reporter, LoadCommandTooShort(_, _)).Times(0);
+    EXPECT_CALL(reporter, SectionsMissing(_)).Times(0);
+    EXPECT_CALL(reporter, MisplacedSegmentData(_)).Times(0);
+    EXPECT_CALL(reporter, MisplacedSectionData(_, _)).Times(0);
+    EXPECT_CALL(reporter, MisplacedSymbolTable()).Times(0);
+    EXPECT_CALL(reporter, UnsupportedCPUType(_)).Times(0);
+
+    EXPECT_CALL(load_command_handler, UnknownCommand(_, _)).Times(0);
+    EXPECT_CALL(load_command_handler, SegmentCommand(_)).Times(0);
+  }
+
+  void ReadFile(MachOFile *file,
+                bool expect_parse_success,
+                cpu_type_t expected_cpu_type,
+                cpu_subtype_t expected_cpu_subtype) {
+    ASSERT_TRUE(file->GetContents(&file_contents));
+    file_bytes = reinterpret_cast<const uint8_t *>(file_contents.data());
+    if (expect_parse_success) {
+      EXPECT_TRUE(reader.Read(file_bytes,
+                              file_contents.size(),
+                              expected_cpu_type,
+                              expected_cpu_subtype));
+    } else {
+      EXPECT_FALSE(reader.Read(file_bytes,
+                               file_contents.size(),
+                               expected_cpu_type,
+                               expected_cpu_subtype));
+    }
+  }
+
+  string file_contents;
+  const uint8_t *file_bytes;
+  MockReaderReporter reporter;
+  Reader reader;
+  MockLoadCommandHandler load_command_handler;
+  MockSectionHandler section_handler;
+};
+
+class ReaderTest: public ReaderFixture, public Test { };
+
+TEST_F(ReaderTest, BadMagic) {
+  WithConfiguration config(kLittleEndian, 32);
+  const cpu_type_t kCPUType = 0x46b760df;
+  const cpu_subtype_t kCPUSubType = 0x76a0e7f7;
+  MachOFile file;
+  file
+      .D32(0x67bdebe1)                  // Not a proper magic number.
+      .D32(kCPUType)                    // cpu type
+      .D32(kCPUSubType)                 // cpu subtype
+      .D32(0x149fc717)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // they occupy no bytes
+      .D32(0x80e71d64)                  // flags
+      .D32(0);                          // reserved
+  EXPECT_CALL(reporter, BadHeader()).WillOnce(Return());
+  ReadFile(&file, false, CPU_TYPE_ANY, kCPUSubType);
+}
+
+TEST_F(ReaderTest, MismatchedMagic) {
+  WithConfiguration config(kLittleEndian, 32);
+  const cpu_type_t kCPUType = CPU_TYPE_I386;
+  const cpu_subtype_t kCPUSubType = CPU_SUBTYPE_X86_ALL;
+  MachOFile file;
+  file
+      .D32(MH_CIGAM)                    // Right magic, but winds up wrong
+                                        // due to bitswapping
+      .D32(kCPUType)                    // cpu type
+      .D32(kCPUSubType)                 // cpu subtype
+      .D32(0x149fc717)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // they occupy no bytes
+      .D32(0x80e71d64)                  // flags
+      .D32(0);                          // reserved
+  EXPECT_CALL(reporter, BadHeader()).WillOnce(Return());
+  ReadFile(&file, false, kCPUType, kCPUSubType);
+}
+
+TEST_F(ReaderTest, ShortMagic) {
+  WithConfiguration config(kBigEndian, 32);
+  MachOFile file;
+  file
+      .D16(0xfeed);                     // magic number
+                                        // truncated!
+  EXPECT_CALL(reporter, HeaderTruncated()).WillOnce(Return());
+  ReadFile(&file, false, CPU_TYPE_ANY, 0);
+}
+
+TEST_F(ReaderTest, ShortHeader) {
+  WithConfiguration config(kBigEndian, 32);
+  const cpu_type_t kCPUType = CPU_TYPE_ANY;
+  const cpu_subtype_t kCPUSubType = 0x76a0e7f7;
+  MachOFile file;
+  file
+      .D32(0xfeedface)                  // magic number
+      .D32(kCPUType)                    // cpu type
+      .D32(kCPUSubType)                 // cpu subtype
+      .D32(0x149fc717)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0);                          // they occupy no bytes
+  EXPECT_CALL(reporter, HeaderTruncated()).WillOnce(Return());
+  ReadFile(&file, false, CPU_TYPE_ANY, kCPUSubType);
+}
+
+TEST_F(ReaderTest, MismatchedCPU) {
+  WithConfiguration config(kBigEndian, 32);
+  const cpu_type_t kCPUType = CPU_TYPE_I386;
+  const cpu_subtype_t kCPUSubType = CPU_SUBTYPE_X86_ALL;
+  MachOFile file;
+  file
+      .D32(MH_MAGIC)                    // Right magic for PPC (once bitswapped)
+      .D32(kCPUType)                    // cpu type
+      .D32(kCPUSubType)                 // cpu subtype
+      .D32(0x149fc717)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // they occupy no bytes
+      .D32(0x80e71d64)                  // flags
+      .D32(0);                          // reserved
+  EXPECT_CALL(reporter,
+              CPUTypeMismatch(CPU_TYPE_I386, CPU_SUBTYPE_X86_ALL,
+                              CPU_TYPE_POWERPC, CPU_SUBTYPE_POWERPC_ALL))
+    .WillOnce(Return());
+  ReadFile(&file, false, CPU_TYPE_POWERPC, CPU_SUBTYPE_POWERPC_ALL);
+}
+
+TEST_F(ReaderTest, LittleEndian32Bit) {
+  WithConfiguration config(kLittleEndian, 32);
+  const cpu_type_t kCPUType = 0x46b760df;
+  const cpu_subtype_t kCPUSubType = 0x76a0e7f7;
+  MachOFile file;
+  file
+      .D32(0xfeedface)                  // magic number
+      .D32(kCPUType)                    // cpu type
+      .D32(kCPUSubType)                 // cpu subtype
+      .D32(0x149fc717)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // they occupy no bytes
+      .D32(0x80e71d64)                  // flags
+      .D32(0);                          // reserved
+           ReadFile(&file, true, CPU_TYPE_ANY, kCPUSubType);
+  EXPECT_FALSE(reader.bits_64());
+  EXPECT_FALSE(reader.big_endian());
+  EXPECT_EQ(kCPUType,               reader.cpu_type());
+  EXPECT_EQ(kCPUSubType,            reader.cpu_subtype());
+  EXPECT_EQ(FileType(0x149fc717),   reader.file_type());
+  EXPECT_EQ(FileFlags(0x80e71d64),  reader.flags());
+}
+
+TEST_F(ReaderTest, LittleEndian64Bit) {
+  WithConfiguration config(kLittleEndian, 64);
+  const cpu_type_t kCPUType = 0x46b760df;
+  const cpu_subtype_t kCPUSubType = 0x76a0e7f7;
+  MachOFile file;
+  file
+      .D32(0xfeedfacf)                  // magic number
+      .D32(kCPUType)                    // cpu type
+      .D32(kCPUSubType)                 // cpu subtype
+      .D32(0x149fc717)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // they occupy no bytes
+      .D32(0x80e71d64)                  // flags
+      .D32(0);                          // reserved
+  ReadFile(&file, true, CPU_TYPE_ANY, kCPUSubType);
+  EXPECT_TRUE(reader.bits_64());
+  EXPECT_FALSE(reader.big_endian());
+  EXPECT_EQ(kCPUType,               reader.cpu_type());
+  EXPECT_EQ(kCPUSubType,            reader.cpu_subtype());
+  EXPECT_EQ(FileType(0x149fc717),   reader.file_type());
+  EXPECT_EQ(FileFlags(0x80e71d64),  reader.flags());
+}
+
+TEST_F(ReaderTest, BigEndian32Bit) {
+  WithConfiguration config(kBigEndian, 32);
+  const cpu_type_t kCPUType = 0x46b760df;
+  const cpu_subtype_t kCPUSubType = 0x76a0e7f7;
+  MachOFile file;
+  file
+      .D32(0xfeedface)                  // magic number
+      .D32(kCPUType)                    // cpu type
+      .D32(kCPUSubType)                 // cpu subtype
+      .D32(0x149fc717)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // they occupy no bytes
+      .D32(0x80e71d64)                  // flags
+      .D32(0);                          // reserved
+  ReadFile(&file, true, CPU_TYPE_ANY, kCPUSubType);
+  EXPECT_FALSE(reader.bits_64());
+  EXPECT_TRUE(reader.big_endian());
+  EXPECT_EQ(kCPUType,               reader.cpu_type());
+  EXPECT_EQ(kCPUSubType,            reader.cpu_subtype());
+  EXPECT_EQ(FileType(0x149fc717),   reader.file_type());
+  EXPECT_EQ(FileFlags(0x80e71d64),  reader.flags());
+}
+
+TEST_F(ReaderTest, BigEndian64Bit) {
+  WithConfiguration config(kBigEndian, 64);
+  const cpu_type_t kCPUType = 0x46b760df;
+  const cpu_subtype_t kCPUSubType = 0x76a0e7f7;
+  MachOFile file;
+  file
+      .D32(0xfeedfacf)                  // magic number
+      .D32(kCPUType)                    // cpu type
+      .D32(kCPUSubType)                 // cpu subtype
+      .D32(0x149fc717)                  // file type
+      .D32(0)                           // no load commands
+      .D32(0)                           // they occupy no bytes
+      .D32(0x80e71d64)                  // flags
+      .D32(0);                          // reserved
+  ReadFile(&file, true, CPU_TYPE_ANY, kCPUSubType);
+  EXPECT_TRUE(reader.bits_64());
+  EXPECT_TRUE(reader.big_endian());
+  EXPECT_EQ(kCPUType,               reader.cpu_type());
+  EXPECT_EQ(kCPUSubType,            reader.cpu_subtype());
+  EXPECT_EQ(FileType(0x149fc717),   reader.file_type());
+  EXPECT_EQ(FileFlags(0x80e71d64),  reader.flags());
+}
+
+
+// Load command tests.
+
+class LoadCommand: public ReaderFixture, public Test { };
+
+TEST_F(LoadCommand, RegionTruncated) {
+  WithConfiguration config(kBigEndian, 64);
+  const cpu_type_t kCPUType = 0x46b760df;
+  const cpu_subtype_t kCPUSubType = 0x76a0e7f7;
+  MachOFile file;
+  file
+      .D32(0xfeedfacf)                  // magic number
+      .D32(kCPUType)                    // cpu type
+      .D32(kCPUSubType)                 // cpu subtype
+      .D32(0x149fc717)                  // file type
+      .D32(1)                           // one load command
+      .D32(40)                          // occupying 40 bytes
+      .D32(0x80e71d64)                  // flags
+      .D32(0)                           // reserved
+      .Append(20, 0);                   // load command region, not as long as
+                                        // Mach-O header promised
+
+  EXPECT_CALL(reporter, LoadCommandRegionTruncated()).WillOnce(Return());
+
+  ReadFile(&file, false, CPU_TYPE_ANY, kCPUSubType);
+}
+
+TEST_F(LoadCommand, None) {
+  WithConfiguration config(kLittleEndian, 32);
+  LoadCommands load_commands;
+  MachOFile file;
+  file.Header(&load_commands);
+
+  ReadFile(&file, true, CPU_TYPE_X86, CPU_SUBTYPE_I386_ALL);
+
+  EXPECT_FALSE(reader.bits_64());
+  EXPECT_FALSE(reader.big_endian());
+  EXPECT_EQ(CPU_TYPE_X86,         reader.cpu_type());
+  EXPECT_EQ(CPU_SUBTYPE_I386_ALL, reader.cpu_subtype());
+  EXPECT_EQ(MH_EXECUTE,           reader.file_type());
+  EXPECT_EQ(FileFlags(MH_TWOLEVEL |
+                      MH_DYLDLINK |
+                      MH_NOUNDEFS),
+            FileFlags(reader.flags()));
+  
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+}
+
+TEST_F(LoadCommand, Unknown) {
+  WithConfiguration config(kBigEndian, 32);
+  LoadCommands load_commands;
+  load_commands
+      .CountCommand()
+      .D32(0x33293d4a)                  // unknown load command
+      .D32(40)                          // total size in bytes
+      .Append(32, '*');                 // dummy data
+  MachOFile file;
+  file.Header(&load_commands);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  EXPECT_FALSE(reader.bits_64());
+  EXPECT_TRUE(reader.big_endian());
+  EXPECT_EQ(CPU_TYPE_X86,         reader.cpu_type());
+  EXPECT_EQ(CPU_SUBTYPE_I386_ALL, reader.cpu_subtype());
+  EXPECT_EQ(MH_EXECUTE,           reader.file_type());
+  EXPECT_EQ(FileFlags(MH_TWOLEVEL |
+                      MH_DYLDLINK |
+                      MH_NOUNDEFS),
+            reader.flags());
+
+  ByteBuffer expected;
+  expected.start = file_bytes + load_commands.start().Value();
+  expected.end = expected.start + load_commands.final_size().Value();
+  EXPECT_CALL(load_command_handler, UnknownCommand(0x33293d4a,
+                                                   expected))
+      .WillOnce(Return(true));
+
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+}
+
+TEST_F(LoadCommand, TypeIncomplete) {
+  WithConfiguration config(kLittleEndian, 32);
+  LoadCommands load_commands;
+  load_commands
+      .CountCommand()
+      .Append(3, 0);                    // load command type, incomplete
+
+  MachOFile file;
+  file.Header(&load_commands);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  EXPECT_CALL(reporter, LoadCommandsOverrun(1, 0, 0))
+      .WillOnce(Return());
+  EXPECT_FALSE(reader.WalkLoadCommands(&load_command_handler));
+}
+
+TEST_F(LoadCommand, LengthIncomplete) {
+  WithConfiguration config(kBigEndian, 64);
+  LoadCommands load_commands;
+  load_commands
+      .CountCommand()
+      .D32(LC_SEGMENT);                 // load command
+                                                // no length
+  MachOFile file;
+  file.Header(&load_commands);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  EXPECT_CALL(reporter, LoadCommandsOverrun(1, 0, LC_SEGMENT))
+      .WillOnce(Return());
+  EXPECT_FALSE(reader.WalkLoadCommands(&load_command_handler));
+}
+
+TEST_F(LoadCommand, ContentIncomplete) {
+  WithConfiguration config(kLittleEndian, 64);
+  LoadCommands load_commands;
+  load_commands
+      .CountCommand()
+      .D32(LC_SEGMENT)          // load command
+      .D32(40)                          // total size in bytes
+      .Append(28, '*');                 // not enough dummy data
+  MachOFile file;
+  file.Header(&load_commands);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  EXPECT_CALL(reporter, LoadCommandsOverrun(1, 0, LC_SEGMENT))
+      .WillOnce(Return());
+  EXPECT_FALSE(reader.WalkLoadCommands(&load_command_handler));
+}
+
+TEST_F(LoadCommand, SegmentBE32) {
+  WithConfiguration config(kBigEndian, 32);
+  LoadedSection segment;
+  segment.address() = 0x1891139c;
+  segment.Append(42, '*');              // segment contents
+  SegmentLoadCommand segment_command;
+  segment_command
+      .Header("froon", segment, 0x94d6dd22, 0x8bdbc319, 0x990a16dd);
+  segment_command.vmsize() = 0xcb76584fU;
+  LoadCommands load_commands;
+  load_commands.Place(&segment_command);
+  MachOFile file;
+  file
+      .Header(&load_commands)
+      .Place(&segment);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment actual_segment;
+  EXPECT_CALL(load_command_handler, SegmentCommand(_))
+    .WillOnce(DoAll(SaveArg<0>(&actual_segment),
+                    Return(true)));
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+
+  EXPECT_EQ(false,                        actual_segment.bits_64);
+  EXPECT_EQ("froon",                      actual_segment.name);
+  EXPECT_EQ(0x1891139cU,                  actual_segment.vmaddr);
+  EXPECT_EQ(0xcb76584fU,                  actual_segment.vmsize);
+  EXPECT_EQ(0x94d6dd22U,                  actual_segment.maxprot);
+  EXPECT_EQ(0x8bdbc319U,                  actual_segment.initprot);
+  EXPECT_EQ(0x990a16ddU,                  actual_segment.flags);
+  EXPECT_EQ(0U,                           actual_segment.nsects);
+  EXPECT_EQ(0U,                           actual_segment.section_list.Size());
+  EXPECT_EQ(segment.final_size().Value(), actual_segment.contents.Size());
+}
+
+TEST_F(LoadCommand, SegmentLE32) {
+  WithConfiguration config(kLittleEndian, 32);
+  LoadedSection segment;
+  segment.address() = 0x4b877866;
+  segment.Append(42, '*');              // segment contents
+  SegmentLoadCommand segment_command;
+  segment_command
+      .Header("sixteenprecisely", segment,
+              0x350759ed, 0x6cf5a62e, 0x990a16dd);
+  segment_command.vmsize() = 0xcb76584fU;
+  LoadCommands load_commands;
+  load_commands.Place(&segment_command);
+  MachOFile file;
+  file
+      .Header(&load_commands)
+      .Place(&segment);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment actual_segment;
+  EXPECT_CALL(load_command_handler, SegmentCommand(_))
+    .WillOnce(DoAll(SaveArg<0>(&actual_segment),
+                    Return(true)));
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+
+  EXPECT_EQ(false,                        actual_segment.bits_64);
+  EXPECT_EQ("sixteenprecisely",           actual_segment.name);
+  EXPECT_EQ(0x4b877866U,                  actual_segment.vmaddr);
+  EXPECT_EQ(0xcb76584fU,                  actual_segment.vmsize);
+  EXPECT_EQ(0x350759edU,                  actual_segment.maxprot);
+  EXPECT_EQ(0x6cf5a62eU,                  actual_segment.initprot);
+  EXPECT_EQ(0x990a16ddU,                  actual_segment.flags);
+  EXPECT_EQ(0U,                           actual_segment.nsects);
+  EXPECT_EQ(0U,                           actual_segment.section_list.Size());
+  EXPECT_EQ(segment.final_size().Value(), actual_segment.contents.Size());
+}
+
+TEST_F(LoadCommand, SegmentBE64) {
+  WithConfiguration config(kBigEndian, 64);
+  LoadedSection segment;
+  segment.address() = 0x79f484f77009e511ULL;
+  segment.Append(42, '*');              // segment contents
+  SegmentLoadCommand segment_command;
+  segment_command
+      .Header("froon", segment, 0x42b45da5, 0x8bdbc319, 0xb2335220);
+  segment_command.vmsize() = 0x8d92397ce6248abaULL;
+  LoadCommands load_commands;
+  load_commands.Place(&segment_command);
+  MachOFile file;
+  file
+      .Header(&load_commands)
+      .Place(&segment);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment actual_segment;
+  EXPECT_CALL(load_command_handler, SegmentCommand(_))
+    .WillOnce(DoAll(SaveArg<0>(&actual_segment),
+                    Return(true)));
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+
+  EXPECT_EQ(true,                         actual_segment.bits_64);
+  EXPECT_EQ("froon",                      actual_segment.name);
+  EXPECT_EQ(0x79f484f77009e511ULL,        actual_segment.vmaddr);
+  EXPECT_EQ(0x8d92397ce6248abaULL,        actual_segment.vmsize);
+  EXPECT_EQ(0x42b45da5U,                  actual_segment.maxprot);
+  EXPECT_EQ(0x8bdbc319U,                  actual_segment.initprot);
+  EXPECT_EQ(0xb2335220U,                  actual_segment.flags);
+  EXPECT_EQ(0U,                           actual_segment.nsects);
+  EXPECT_EQ(0U,                           actual_segment.section_list.Size());
+  EXPECT_EQ(segment.final_size().Value(), actual_segment.contents.Size());
+}
+
+TEST_F(LoadCommand, SegmentLE64) {
+  WithConfiguration config(kLittleEndian, 64);
+  LoadedSection segment;
+  segment.address() = 0x50c0501dc5922d35ULL;
+  segment.Append(42, '*');              // segment contents
+  SegmentLoadCommand segment_command;
+  segment_command
+      .Header("sixteenprecisely", segment,
+              0x917c339d, 0xdbc446fa, 0xb650b563);
+  segment_command.vmsize() = 0x84ae73e7c75469bfULL;
+  LoadCommands load_commands;
+  load_commands.Place(&segment_command);
+  MachOFile file;
+  file
+      .Header(&load_commands)
+      .Place(&segment);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment actual_segment;
+  EXPECT_CALL(load_command_handler, SegmentCommand(_))
+    .WillOnce(DoAll(SaveArg<0>(&actual_segment),
+                    Return(true)));
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+
+  EXPECT_EQ(true,                         actual_segment.bits_64);
+  EXPECT_EQ("sixteenprecisely",           actual_segment.name);
+  EXPECT_EQ(0x50c0501dc5922d35ULL,        actual_segment.vmaddr);
+  EXPECT_EQ(0x84ae73e7c75469bfULL,        actual_segment.vmsize);
+  EXPECT_EQ(0x917c339dU,                  actual_segment.maxprot);
+  EXPECT_EQ(0xdbc446faU,                  actual_segment.initprot);
+  EXPECT_EQ(0xb650b563U,                  actual_segment.flags);
+  EXPECT_EQ(0U,                           actual_segment.nsects);
+  EXPECT_EQ(0U,                           actual_segment.section_list.Size());
+  EXPECT_EQ(segment.final_size().Value(), actual_segment.contents.Size());
+}
+
+TEST_F(LoadCommand, SegmentCommandTruncated) {
+  WithConfiguration config(kBigEndian, 32);
+  LoadedSection segment_contents;
+  segment_contents.Append(20, '*');     	// lah di dah
+  SizedSection command;
+  command
+      .D32(LC_SEGMENT)          	// command type
+      .D32(command.final_size())                // command size
+      .AppendCString("too-short", 16)           // segment name
+      .D32(0x9c759211)                          // vmaddr
+      .D32(segment_contents.final_size())       // vmsize
+      .D32(segment_contents.start())            // file offset
+      .D32(segment_contents.final_size())       // file size
+      .D32(0x56f28446)                          // max protection
+      .D32(0xe7910dcb)                          // initial protection
+      .D32(0)                                   // no sections
+      .Append(3, 0);                            // flags (one byte short!)
+  LoadCommands load_commands;
+  load_commands.Place(&command);
+  MachOFile file;
+  file
+      .Header(&load_commands)
+      .Place(&segment_contents);
+  
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  EXPECT_CALL(reporter, LoadCommandTooShort(0, LC_SEGMENT))
+      .WillOnce(Return());
+
+  EXPECT_FALSE(reader.WalkLoadCommands(&load_command_handler));
+}
+
+TEST_F(LoadCommand, SegmentBadContentOffset) {
+  WithConfiguration config(kLittleEndian, 32);
+  // Instead of letting a Place call set the segment's file offset and size,
+  // set them ourselves, to check that the parser catches invalid offsets
+  // instead of handing us bogus pointers.
+  LoadedSection segment;
+  segment.address() = 0x4db5489c;
+  segment.start() = 0x7e189e76;         // beyond end of file
+  segment.final_size() = 0x98b9c3ab;
+  SegmentLoadCommand segment_command;
+  segment_command
+      .Header("notmerelyfifteen", segment, 0xcbab25ee, 0x359a20db, 0x68a3933f);
+  LoadCommands load_commands;
+  load_commands.Place(&segment_command);
+  MachOFile file;
+  file.Header(&load_commands);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  EXPECT_CALL(reporter, MisplacedSegmentData("notmerelyfifteen"))
+      .WillOnce(Return());
+
+  EXPECT_FALSE(reader.WalkLoadCommands(&load_command_handler));
+}
+
+TEST_F(LoadCommand, ThreeLoadCommands) {
+  WithConfiguration config(kBigEndian, 32);
+  LoadedSection seg1, seg2, seg3;
+  SegmentLoadCommand cmd1, cmd2, cmd3;
+
+  seg1.Append(128, '@');
+  seg1.address() = 0xa7f61ef6;
+  cmd1.Header("head", seg1, 0x88bf1cc7, 0x889a26a4, 0xe9b80d87);
+  // Include some dummy data at the end of the load command. Since we
+  // didn't claim to have any sections, the reader should ignore this. But
+  // making sure the commands have different lengths ensures that we're
+  // using the right command's length to advance the LoadCommandIterator.
+  cmd1.Append(128, '!');
+
+  seg2.Append(42, '*');
+  seg2.address() = 0xc70fc909;
+  cmd2.Header("thorax", seg2, 0xde7327f4, 0xfdaf771d, 0x65e74b30);
+  // More dummy data at the end of the load command. 
+  cmd2.Append(32, '^');
+
+  seg3.Append(42, '%');
+  seg3.address() = 0x46b3ab05;
+  cmd3.Header("abdomen", seg3, 0x7098b70d, 0x8d8d7728, 0x5131419b);
+  // More dummy data at the end of the load command. 
+  cmd3.Append(64, '&');
+
+  LoadCommands load_commands;
+  load_commands.Place(&cmd1).Place(&cmd2).Place(&cmd3);
+
+  MachOFile file;
+  file.Header(&load_commands).Place(&seg1).Place(&seg2).Place(&seg3);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  {
+    InSequence s;
+    EXPECT_CALL(load_command_handler,
+                SegmentCommand(Field(&Segment::name, "head")))
+      .WillOnce(Return(true));
+    EXPECT_CALL(load_command_handler,
+                SegmentCommand(Field(&Segment::name, "thorax")))
+      .WillOnce(Return(true));
+    EXPECT_CALL(load_command_handler,
+                SegmentCommand(Field(&Segment::name, "abdomen")))
+      .WillOnce(Return(true));
+  }
+
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+}
+
+static inline Matcher<const Section &> MatchSection(
+    Matcher<bool> bits_64,
+    Matcher<const string &> section_name,
+    Matcher<const string &> segment_name,
+    Matcher<uint64_t> address,
+    Matcher<uint32_t> alignment,
+    Matcher<uint32_t> flags,
+    Matcher<const ByteBuffer &> contents) {
+  return AllOf(AllOf(Field(&Section::bits_64, bits_64),
+                     Field(&Section::section_name, section_name),
+                     Field(&Section::segment_name, segment_name),
+                     Field(&Section::address, address)),
+               AllOf(Field(&Section::align, alignment),
+                     Field(&Section::flags, flags),
+                     Field(&Section::contents, contents)));
+}
+
+static inline Matcher<const Section &> MatchSection(
+    Matcher<bool> bits_64,
+    Matcher<const string &> section_name,
+    Matcher<const string &> segment_name,
+    Matcher<uint64_t> address) {
+  return AllOf(Field(&Section::bits_64, bits_64),
+               Field(&Section::section_name, section_name),
+               Field(&Section::segment_name, segment_name),
+               Field(&Section::address, address));
+}
+
+TEST_F(LoadCommand, OneSegmentTwoSections) {
+  WithConfiguration config(kBigEndian, 64);
+
+  // Create some sections with some data.
+  LoadedSection section1, section2;
+  section1.Append("buddha's hand");
+  section2.Append("kumquat");
+
+  // Create a segment to hold them.
+  LoadedSection segment;
+  segment.address() = 0xe1d0eeec;
+  segment.Place(&section2).Place(&section1);
+
+  SegmentLoadCommand segment_command;
+  segment_command
+      .Header("head", segment, 0x92c9568c, 0xa89f2627, 0x4dc7a1e2)
+      .AppendSectionEntry("mandarin", "kishu", 12, 0x8cd4604bU, section1)
+      .AppendSectionEntry("bergamot", "cara cara", 12, 0x98746efaU, section2);
+
+  LoadCommands commands;
+  commands.Place(&segment_command);
+
+  MachOFile file;
+  file.Header(&commands).Place(&segment);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+  
+  Segment actual_segment;
+  EXPECT_CALL(load_command_handler, SegmentCommand(_))
+      .WillOnce(DoAll(SaveArg<0>(&actual_segment),
+                      Return(true)));
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+
+  {
+    InSequence s;
+    ByteBuffer contents1;
+    contents1.start = file_bytes + section1.start().Value();
+    contents1.end = contents1.start + section1.final_size().Value();
+    EXPECT_EQ("buddha's hand",
+              string(reinterpret_cast<const char *>(contents1.start),
+                     contents1.Size()));
+    EXPECT_CALL(section_handler,
+                HandleSection(MatchSection(true, "mandarin", "kishu",
+                                           section1.address().Value(), 12,
+                                           0x8cd4604bU, contents1)))
+      .WillOnce(Return(true));
+    
+    ByteBuffer contents2;
+    contents2.start = file_bytes + section2.start().Value();
+    contents2.end = contents2.start + section2.final_size().Value();
+    EXPECT_EQ("kumquat",
+              string(reinterpret_cast<const char *>(contents2.start),
+                     contents2.Size()));
+    EXPECT_CALL(section_handler,
+                HandleSection(MatchSection(true, "bergamot", "cara cara",
+                                           section2.address().Value(), 12,
+                                           0x98746efaU, contents2)))
+      .WillOnce(Return(true));
+  }
+
+  EXPECT_TRUE(reader.WalkSegmentSections(actual_segment, &section_handler));
+}
+
+TEST_F(LoadCommand, MisplacedSectionBefore) {
+  WithConfiguration config(kLittleEndian, 64);
+
+  // The segment.
+  LoadedSection segment;
+  segment.address() = 0x696d83cc;
+  segment.Append(10, '0');
+
+  // The contents of the following sections don't matter, because
+  // we're not really going to Place them in segment; we're just going
+  // to set all their labels by hand to get the (impossible)
+  // configurations we want.
+
+  // A section whose starting offset is before that of its section.
+  LoadedSection before;
+  before.Append(10, '1');
+  before.start()   = segment.start() - 1;
+  before.address() = segment.address() - 1;
+  before.final_size() = before.Size();
+  
+  SegmentLoadCommand command;
+  command
+    .Header("segment", segment, 0x173baa29, 0x8407275d, 0xed8f7057)
+    .AppendSectionEntry("before",     "segment", 0, 0x686c6921, before);
+
+  LoadCommands commands;
+  commands.Place(&command);
+
+  MachOFile file;
+  file.Header(&commands).Place(&segment);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment actual_segment;
+  EXPECT_TRUE(reader.FindSegment("segment", &actual_segment));
+
+  EXPECT_CALL(reporter, MisplacedSectionData("before", "segment"))
+    .WillOnce(Return());
+  EXPECT_FALSE(reader.WalkSegmentSections(actual_segment, &section_handler));
+}
+
+TEST_F(LoadCommand, MisplacedSectionAfter) {
+  WithConfiguration config(kLittleEndian, 64);
+
+  // The segment.
+  LoadedSection segment;
+  segment.address() = 0x696d83cc;
+  segment.Append(10, '0');
+
+  // The contents of the following sections don't matter, because
+  // we're not really going to Place them in segment; we're just going
+  // to set all their labels by hand to get the (impossible)
+  // configurations we want.
+
+  // A section whose starting offset is after the end of its section.
+  LoadedSection after;
+  after.Append(10, '2');
+  after.start()    = segment.start() + 11;
+  after.address()   = segment.address() + 11;
+  after.final_size() = after.Size();
+
+  SegmentLoadCommand command;
+  command
+    .Header("segment", segment, 0x173baa29, 0x8407275d, 0xed8f7057)
+    .AppendSectionEntry("after",      "segment", 0, 0x2ee50124, after);
+
+  LoadCommands commands;
+  commands.Place(&command);
+
+  MachOFile file;
+  file.Header(&commands).Place(&segment);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment actual_segment;
+  EXPECT_TRUE(reader.FindSegment("segment", &actual_segment));
+
+  EXPECT_CALL(reporter, MisplacedSectionData("after", "segment"))
+    .WillOnce(Return());
+  EXPECT_FALSE(reader.WalkSegmentSections(actual_segment, &section_handler));
+}
+
+TEST_F(LoadCommand, MisplacedSectionTooBig) {
+  WithConfiguration config(kLittleEndian, 64);
+
+  // The segment.
+  LoadedSection segment;
+  segment.address() = 0x696d83cc;
+  segment.Append(10, '0');
+
+  // The contents of the following sections don't matter, because
+  // we're not really going to Place them in segment; we're just going
+  // to set all their labels by hand to get the (impossible)
+  // configurations we want.
+
+  // A section that extends beyond the end of its section.
+  LoadedSection too_big;
+  too_big.Append(10, '3');
+  too_big.start()   = segment.start() + 1;
+  too_big.address() = segment.address() + 1;
+  too_big.final_size() = too_big.Size();
+
+  SegmentLoadCommand command;
+  command
+    .Header("segment", segment, 0x173baa29, 0x8407275d, 0xed8f7057)
+    .AppendSectionEntry("too big",    "segment", 0, 0x8b53ae5c, too_big);
+
+  LoadCommands commands;
+  commands.Place(&command);
+
+  MachOFile file;
+  file.Header(&commands).Place(&segment);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment actual_segment;
+  EXPECT_TRUE(reader.FindSegment("segment", &actual_segment));
+
+  EXPECT_CALL(reporter, MisplacedSectionData("too big", "segment"))
+    .WillOnce(Return());
+  EXPECT_FALSE(reader.WalkSegmentSections(actual_segment, &section_handler));
+}
+
+
+// The segments in a .dSYM bundle's Mach-O file have their file offset
+// and size set to zero, but the sections don't.  The reader shouldn't
+// report an error in this case.
+TEST_F(LoadCommand, ZappedSegment) {
+  WithConfiguration config(kBigEndian, 32);
+
+  // The segment.
+  LoadedSection segment;
+  segment.address() = 0x696d83cc;
+  segment.start() = 0;
+  segment.final_size() = 0;
+
+  // The section.
+  LoadedSection section;
+  section.address() = segment.address();
+  section.start() = 0;
+  section.final_size() = 1000;          // extends beyond its segment
+  
+  SegmentLoadCommand command;
+  command
+    .Header("zapped", segment, 0x0861a5cb, 0x68ccff67, 0x0b66255c)
+    .AppendSectionEntry("twitching", "zapped", 0, 0x93b3bd42, section);
+
+  LoadCommands commands;
+  commands.Place(&command);
+
+  MachOFile file;
+  file.Header(&commands);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment actual_segment;
+  EXPECT_TRUE(reader.FindSegment("zapped", &actual_segment));
+
+  ByteBuffer zapped_extent(NULL, 0);
+  EXPECT_CALL(section_handler,
+              HandleSection(MatchSection(false, "twitching", "zapped",
+                                         0x696d83cc, 0, 0x93b3bd42,
+                                         zapped_extent)))
+    .WillOnce(Return(true));
+
+  EXPECT_TRUE(reader.WalkSegmentSections(actual_segment, &section_handler));
+}
+
+TEST_F(LoadCommand, MapSegmentSections) {
+  WithConfiguration config(kLittleEndian, 32);
+
+  // Create some sections with some data.
+  LoadedSection section1, section2, section3, section4;
+  section1.Append("buddha's hand");
+  section2.start() = 0;                 // Section 2 is an S_ZEROFILL section.
+  section2.final_size() = 0;
+  section3.Append("shasta gold");
+  section4.Append("satsuma");
+
+  // Create two segments to hold them.
+  LoadedSection segment1, segment2;
+  segment1.address() = 0x13e6c8a9;
+  segment1.Place(&section3).Place(&section1);
+  segment2.set_word_size(64);
+  segment2.address() = 0x04d462e2;
+  segment2.Place(&section4);
+  section2.address() = segment2.address() + segment2.Size();
+
+  SegmentLoadCommand segment_command1, segment_command2;
+  segment_command1
+      .Header("head", segment1, 0x67d955a6, 0x7a61c13e, 0xe3e50c64)
+      .AppendSectionEntry("mandarin", "head", 12, 0x5bb565d7, section1)
+      .AppendSectionEntry("bergamot", "head", 12, 0x8620de73, section3);
+  segment_command2.set_word_size(64);
+  segment_command2
+      .Header("thorax", segment2, 0x7aab2419, 0xe908007f, 0x17961d33)
+      .AppendSectionEntry("sixteenprecisely", "thorax",
+                          12, S_ZEROFILL, section2)
+      .AppendSectionEntry("cara cara", "thorax", 12, 0xb6c5dd8a, section4);
+
+  LoadCommands commands;
+  commands.Place(&segment_command1).Place(&segment_command2);
+
+  MachOFile file;
+  file.Header(&commands).Place(&segment1).Place(&segment2);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment segment;
+  SectionMap section_map;
+
+  EXPECT_FALSE(reader.FindSegment("smoot", &segment));
+
+  ASSERT_TRUE(reader.FindSegment("thorax", &segment));
+  ASSERT_TRUE(reader.MapSegmentSections(segment, &section_map));
+
+  EXPECT_FALSE(section_map.find("sixteenpreciselyandthensome")
+               != section_map.end());
+  EXPECT_FALSE(section_map.find("mandarin") != section_map.end());
+  ASSERT_TRUE(section_map.find("cara cara") != section_map.end());
+  EXPECT_THAT(section_map["cara cara"],
+              MatchSection(true, "cara cara", "thorax", 0x04d462e2));
+  ASSERT_TRUE(section_map.find("sixteenprecisely")
+              != section_map.end());
+  ByteBuffer sixteenprecisely_contents(NULL, 0);
+  EXPECT_THAT(section_map["sixteenprecisely"],
+              MatchSection(true, "sixteenprecisely", "thorax",
+                           0x04d462e2 + 7, 12, S_ZEROFILL,
+                           sixteenprecisely_contents));
+
+  ASSERT_TRUE(reader.FindSegment("head", &segment));
+  ASSERT_TRUE(reader.MapSegmentSections(segment, &section_map));
+
+  ASSERT_TRUE(section_map.find("mandarin") != section_map.end());
+  EXPECT_THAT(section_map["mandarin"],
+              MatchSection(false, "mandarin", "head", 0x13e6c8a9 + 11));
+  ASSERT_TRUE(section_map.find("bergamot") != section_map.end());
+  EXPECT_THAT(section_map["bergamot"],
+              MatchSection(false, "bergamot", "head", 0x13e6c8a9));
+}
+
+TEST_F(LoadCommand, FindSegment) {
+  WithConfiguration config(kBigEndian, 32);
+
+  LoadedSection segment1, segment2, segment3;
+  segment1.address() = 0xb8ae5752;
+  segment1.Append("Some contents!");
+  segment2.address() = 0xd6b0ce83;
+  segment2.Append("Different stuff.");
+  segment3.address() = 0x7374fd2a;
+  segment3.Append("Further materials.");
+
+  SegmentLoadCommand cmd1, cmd2, cmd3;
+  cmd1.Header("first",  segment1, 0xfadb6932, 0x175bf529, 0x0de790ad);
+  cmd2.Header("second", segment2, 0xeef716e0, 0xe103a9d7, 0x7d38a8ef);
+  cmd3.Header("third",  segment3, 0xe172b39e, 0x86012f07, 0x080ac94d);
+
+  LoadCommands commands;
+  commands.Place(&cmd1).Place(&cmd2).Place(&cmd3);
+
+  MachOFile file;
+  file.Header(&commands).Place(&segment1).Place(&segment2).Place(&segment3);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  Segment actual_segment;
+
+  EXPECT_FALSE(reader.FindSegment("murphy", &actual_segment));
+
+  EXPECT_TRUE(reader.FindSegment("second", &actual_segment));
+  EXPECT_EQ(0xd6b0ce83, actual_segment.vmaddr);
+}
+
+
+// Symtab tests.
+
+// A StringAssembler is a class for generating .stabstr sections to present
+// as input to the STABS parser.
+class StringAssembler: public SizedSection {
+ public:
+  // Add the string S to this StringAssembler, and return the string's
+  // offset within this compilation unit's strings.
+  size_t Add(const string &s) {
+    size_t offset = Size();
+    AppendCString(s);
+    return offset;
+  }
+};
+
+// A SymbolAssembler is a class for generating .stab sections to present as
+// test input for the STABS parser.
+class SymbolAssembler: public SizedSection {
+ public:
+  // Create a SymbolAssembler that uses StringAssembler for its strings.
+  explicit SymbolAssembler(StringAssembler *string_assembler) 
+      : string_assembler_(string_assembler),
+        entry_count_(0) { }
+
+  // Append a STAB entry to the end of this section with the given
+  // characteristics. NAME is the offset of this entry's name string within
+  // its compilation unit's portion of the .stabstr section; this can be a
+  // value generated by a StringAssembler. Return a reference to this
+  // SymbolAssembler.
+  SymbolAssembler &Symbol(uint8_t type, uint8_t other, Label descriptor,
+                          Label value, Label name) {
+    D32(name);
+    D8(type);
+    D8(other);
+    D16(descriptor);
+    Append(endianness(), word_size_ / 8, value);
+    entry_count_++;
+    return *this;
+  }
+
+  // As above, but automatically add NAME to our StringAssembler.
+  SymbolAssembler &Symbol(uint8_t type, uint8_t other, Label descriptor,
+                       Label value, const string &name) {
+    return Symbol(type, other, descriptor, value, string_assembler_->Add(name));
+  }
+
+ private:
+  // The strings for our STABS entries.
+  StringAssembler *string_assembler_;
+
+  // The number of entries in this compilation unit so far.
+  size_t entry_count_;
+};
+
+class Symtab: public ReaderFixture, public Test { };
+
+TEST_F(Symtab, Symtab32) {
+  WithConfiguration config(kLittleEndian, 32);
+
+  StringAssembler strings;
+  SymbolAssembler symbols(&strings);
+  symbols
+      .Symbol(0x52, 0x7c, 0x3470, 0x9bb02e7c, "hrududu")
+      .Symbol(0x50, 0x90, 0x7520, 0x1122525d, "Frith");
+
+  SizedSection symtab_command;
+  symtab_command
+      .D32(LC_SYMTAB)                    // command
+      .D32(symtab_command.final_size())  // size
+      .D32(symbols.start())              // file offset of symbols
+      .D32(2)                            // symbol count
+      .D32(strings.start())              // file offset of strings
+      .D32(strings.final_size());        // strings size
+
+  LoadCommands load_commands;
+  load_commands.Place(&symtab_command);
+
+  MachOFile file;
+  file.Header(&load_commands).Place(&symbols).Place(&strings);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  ByteBuffer symbols_found, strings_found;
+  EXPECT_CALL(load_command_handler, SymtabCommand(_, _))
+      .WillOnce(DoAll(SaveArg<0>(&symbols_found),
+                      SaveArg<1>(&strings_found),
+                      Return(true)));
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+
+  EXPECT_EQ(24U, symbols_found.Size());
+  EXPECT_EQ(14U, strings_found.Size());
+}
+
+TEST_F(Symtab, Symtab64) {
+  WithConfiguration config(kBigEndian, 64);
+
+  StringAssembler strings;
+  SymbolAssembler symbols(&strings);
+  symbols
+      .Symbol(0xa7, 0xaf, 0x03af, 0x42f3072c74335181ULL, "foo")
+      .Symbol(0xb0, 0x9a, 0x2aa7, 0x2e2d349b3d5744a0ULL, "bar");
+
+  SizedSection symtab_command;
+  symtab_command
+      .D32(LC_SYMTAB)                    // command
+      .D32(symtab_command.final_size())  // size
+      .D32(symbols.start())              // file offset of symbols
+      .D32(2)                            // symbol count
+      .D32(strings.start())              // file offset of strings
+      .D32(strings.final_size());        // strings size
+
+  LoadCommands load_commands;
+  load_commands.Place(&symtab_command);
+
+  MachOFile file;
+  file.Header(&load_commands).Place(&symbols).Place(&strings);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  ByteBuffer symbols_found, strings_found;
+  EXPECT_CALL(load_command_handler, SymtabCommand(_, _))
+      .WillOnce(DoAll(SaveArg<0>(&symbols_found),
+                      SaveArg<1>(&strings_found),
+                      Return(true)));
+  EXPECT_TRUE(reader.WalkLoadCommands(&load_command_handler));
+
+  EXPECT_EQ(32U, symbols_found.Size());
+  EXPECT_EQ(8U,  strings_found.Size());
+}
+
+TEST_F(Symtab, SymtabMisplacedSymbols) {
+  WithConfiguration config(kBigEndian, 32);
+
+  StringAssembler strings;
+  SymbolAssembler symbols(&strings);
+  symbols
+      .Symbol(0xa7, 0xaf, 0x03af, 0x42f3072c74335181ULL, "foo")
+      .Symbol(0xb0, 0x9a, 0x2aa7, 0x2e2d349b3d5744a0ULL, "bar");
+
+  SizedSection symtab_command;
+  symtab_command
+      .D32(LC_SYMTAB)                    // command
+      .D32(symtab_command.final_size())  // size
+      .D32(symbols.start())              // file offset of symbols
+      .D32(3)                            // symbol count (too many)
+      .D32(strings.start())              // file offset of strings
+      .D32(strings.final_size());        // strings size
+
+  LoadCommands load_commands;
+  load_commands.Place(&symtab_command);
+
+  MachOFile file;
+  // Put symbols at end, so the excessive length will be noticed.
+  file.Header(&load_commands).Place(&strings).Place(&symbols);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  EXPECT_CALL(reporter, MisplacedSymbolTable()).Times(1);
+  EXPECT_FALSE(reader.WalkLoadCommands(&load_command_handler));
+}
+
+TEST_F(Symtab, SymtabMisplacedStrings) {
+  WithConfiguration config(kLittleEndian, 32);
+
+  StringAssembler strings;
+  SymbolAssembler symbols(&strings);
+  symbols
+      .Symbol(0xa7, 0xaf, 0x03af, 0x42f3072c74335181ULL, "foo")
+      .Symbol(0xb0, 0x9a, 0x2aa7, 0x2e2d349b3d5744a0ULL, "bar");
+
+  SizedSection symtab_command;
+  symtab_command
+      .D32(LC_SYMTAB)                    // command
+      .D32(symtab_command.final_size())  // size
+      .D32(symbols.start())              // file offset of symbols
+      .D32(2)                            // symbol count
+      .D32(strings.start())              // file offset of strings
+      .D32(strings.final_size() + 1);    // strings size (too long)
+
+  LoadCommands load_commands;
+  load_commands.Place(&symtab_command);
+
+  MachOFile file;
+  // Put strings at end, so the excessive length will be noticed.
+  file.Header(&load_commands).Place(&symbols).Place(&strings);
+
+  ReadFile(&file, true, CPU_TYPE_ANY, 0);
+
+  EXPECT_CALL(reporter, MisplacedSymbolTable()).Times(1);
+  EXPECT_FALSE(reader.WalkLoadCommands(&load_command_handler));
+}
+