Add crashpad_info, MachOImageAnnotationsReader, and its test

snapshot/mac/process_reader.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 382 matching lines @@
 
   DCHECK_GE(all_image_infos.version, 1u);
 
   // Note that all_image_infos.infoArrayCount may be 0 if a crash occurred while
   // dyld was loading the executable. This can happen if a required dynamic
   // library was not found. Similarly, all_image_infos.infoArray may be nullptr
   // if a crash occurred while dyld was updating it.
   //
   // TODO(mark): It may be possible to recover from these situations by looking
   // through memory mappings for Mach-O images.
+  //
+  // Continue along when this situation is detected, because even without any
+  // images in infoArray, dyldImageLoadAddress may be set, and it may be
+  // possible to recover some information from dyld.
   if (all_image_infos.infoArrayCount == 0) {
     LOG(WARNING) << "all_image_infos.infoArrayCount is zero";
-    return;
-  }
-  if (!all_image_infos.infoArray) {
+  } else if (!all_image_infos.infoArray) {
     LOG(WARNING) << "all_image_infos.infoArray is nullptr";
-    return;
   }
 
   std::vector<process_types::dyld_image_info> image_info_vector(
       all_image_infos.infoArrayCount);
   if (!process_types::dyld_image_info::ReadArrayInto(this,
                                                      all_image_infos.infoArray,
                                                      image_info_vector.size(),
                                                      &image_info_vector[0])) {
     LOG(WARNING) << "could not read dyld_image_info array";
     return;
@@ skipping 287 matching lines @@
       // The red zone would go lower into another region in memory, but no
       // region was found. Memory can only be captured to an address as low as
       // the base address of the region already found.
       *start_address = *region_base;
     }
   }
 #endif
 }
 
 }  // namespace crashpad