[mac] Teach dump_syms to handle additional zerofill sections

src/common/mac/macho_reader.cc

 // Copyright (c) 2010, Google Inc.

[Mark Mentovai, 2015/09/28 17:59:20]

In the CL description:

https://www.google.com/#q=%22.thread_bss%22

Nobody knows what .thread_bss is. The section name is __DATA,__therad_bss.

[Mark Mentovai, 2015/09/29 12:55:12]

Mark Mentovai - August is over wrote:
The CL description still mentions .thread_bss.

You can edit this with “git cl message” or in the Rietveld web UI by clicking
“Edit Issue”. Local git commit messages don’t influence the CL description once
the CL has been created. The CL description is the only thing that will be used
as the true commit message once committed in the shared repository.

 // 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
@@ skipping 462 matching lines @@
         >> 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) {
+    if ((section.flags & SECTION_TYPE) == S_ZEROFILL || (section.flags & SECTION_TYPE) == S_THREAD_LOCAL_ZEROFILL) {

[Mark Mentovai, 2015/09/28 17:59:20]

Don’t go past 80 columns. Break the line after the ||. Alternatively, this is
also two lines and may be slightly more readable:

  const uint32_t section_type = section.flags & SECTION_TYPE;
  if (section_type == S_ZEROFILL || section_type == S_THREAD_LOCAL_ZEROFILL) {

You may also want to include S_GB_ZEROFILL here.

Reference:
https://chromium.googlesource.com/crashpad/crashpad/+/master/snapshot/mac/mac...

       // 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.
@@ skipping 33 matching lines @@
 
 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