[NaCl SDK] Add some more logging to nacl_io.

native_client_sdk/src/libraries/nacl_io/getdents_helper.cc

 // Copyright (c) 2013 The Chromium 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 "nacl_io/getdents_helper.h"
 
 #include <assert.h>
 #include <errno.h>
 #include <string.h>
 
 #include <algorithm>
 
+#include "nacl_io/log.h"
+
 #include "sdk_util/macros.h"
 
 namespace nacl_io {
 
 GetDentsHelper::GetDentsHelper()
     : curdir_ino_(0), parentdir_ino_(0), init_defaults_(false) {
   Initialize();
 }
 
 GetDentsHelper::GetDentsHelper(ino_t curdir_ino, ino_t parentdir_ino)
@@ skipping 33 matching lines @@
   entry.d_name[copylen] = 0;
 }
 
 Error GetDentsHelper::GetDents(size_t offs,
                                dirent* pdir,
                                size_t size,
                                int* out_bytes) const {
   *out_bytes = 0;
 
   // If the buffer pointer is invalid, fail
-  if (NULL == pdir)
+  if (NULL == pdir) {
+    LOG_TRACE("dirent pointer is NULL.");
     return EINVAL;
+  }
 
   // If the buffer is too small, fail
-  if (size < sizeof(dirent))
+  if (size < sizeof(dirent)) {
+    LOG_TRACE("dirent buffer size is too small: %d < %d", size, sizeof(dirent));
     return EINVAL;
+  }
 
   // Force size to a multiple of dirent
   size -= size % sizeof(dirent);
 
   size_t max = dirents_.size() * sizeof(dirent);
   if (offs >= max) {
     // OK, trying to read past the end.
     return 0;
   }
 
   if (offs + size >= max)
     size = max - offs;
 
   memcpy(pdir, reinterpret_cast<const char*>(dirents_.data()) + offs, size);
   *out_bytes = size;
   return 0;
 }
 
 }  // namespace nacl_io