AIX: Fix 'may be used uninitialized' compiler errors

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 2923 matching lines @@
   return String::cast(*p);
 }
 
 
 bool MarkCompactCollector::TryPromoteObject(HeapObject* object,
                                             int object_size) {
   DCHECK(object_size <= Page::kMaxRegularHeapObjectSize);
 
   OldSpace* old_space = heap()->old_space();
 
-  HeapObject* target;
+  HeapObject* target = nullptr;
   AllocationAlignment alignment = object->RequiredAlignment();
   AllocationResult allocation = old_space->AllocateRaw(object_size, alignment);
   if (allocation.To(&target)) {
     MigrateObject(target, object, object_size, old_space->identity());
     // If we end up needing more special cases, we should factor this out.
     if (V8_UNLIKELY(target->IsJSArrayBuffer())) {
       heap()->PromoteArrayBuffer(target);
     }
     heap()->IncrementPromotedObjectsSize(object_size);
     return true;
@@ skipping 231 matching lines @@
     if (*cell == 0) continue;
 
     int live_objects = MarkWordToObjectStarts(*cell, offsets);
     for (int i = 0; i < live_objects; i++) {
       Address object_addr = cell_base + offsets[i] * kPointerSize;
       HeapObject* object = HeapObject::FromAddress(object_addr);
       DCHECK(Marking::IsBlack(Marking::MarkBitFrom(object)));
 
       int size = object->Size();
       AllocationAlignment alignment = object->RequiredAlignment();
-      HeapObject* target_object;
+      HeapObject* target_object = nullptr;
       AllocationResult allocation = space->AllocateRaw(size, alignment);
       if (!allocation.To(&target_object)) {
         // If allocation failed, use emergency memory and re-try allocation.
         CHECK(space->HasEmergencyMemory());
         space->UseEmergencyMemory();
         allocation = space->AllocateRaw(size, alignment);
       }
       if (!allocation.To(&target_object)) {
         // OS refused to give us memory.
         V8::FatalProcessOutOfMemory("Evacuation");
@@ skipping 1459 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }  // namespace internal
 }  // namespace v8