[NaCl SDK] Add some more logging to nacl_io.

native_client_sdk/src/libraries/nacl_io/dir_node.cc

Index: native_client_sdk/src/libraries/nacl_io/dir_node.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/dir_node.cc b/native_client_sdk/src/libraries/nacl_io/dir_node.cc
index 0486198cc70b3ee25b0a85bd523c7925ac3cac8e..1b1fe15c9c74382799ca27707c449d9ef3de6cab 100644
--- a/native_client_sdk/src/libraries/nacl_io/dir_node.cc
+++ b/native_client_sdk/src/libraries/nacl_io/dir_node.cc
@@ -7,6 +7,7 @@
 #include <errno.h>
 #include <string.h>
 
+#include "nacl_io/log.h"
 #include "nacl_io/osdirent.h"
 #include "nacl_io/osstat.h"
 #include "sdk_util/auto_lock.h"
@@ -40,10 +41,12 @@ Error DirNode::Read(const HandleAttr& attr,
                     size_t count,
                     int* out_bytes) {
   *out_bytes = 0;
+  LOG_TRACE("Can't read a directory.");
   return EISDIR;
 }
 
 Error DirNode::FTruncate(off_t size) {
+  LOG_TRACE("Can't truncate a directory.");
   return EISDIR;
 }
 
@@ -52,6 +55,7 @@ Error DirNode::Write(const HandleAttr& attr,
                      size_t count,
                      int* out_bytes) {
   *out_bytes = 0;
+  LOG_TRACE("Can't write to a directory.");
   return EISDIR;
 }
 
@@ -67,15 +71,23 @@ Error DirNode::GetDents(size_t offs,
 Error DirNode::AddChild(const std::string& name, const ScopedNode& node) {
   AUTO_LOCK(node_lock_);
 
-  if (name.empty())
+  if (name.empty()) {
+    LOG_ERROR("Can't add child with no name.");
     return ENOENT;
+  }
 
-  if (name.length() >= MEMBER_SIZE(dirent, d_name))
+  if (name.length() >= MEMBER_SIZE(dirent, d_name)) {
+    LOG_ERROR("Child name is too long: %d >= %d",
+              name.length(),
+              MEMBER_SIZE(dirent, d_name));
     return ENAMETOOLONG;
+  }
 
   NodeMap_t::iterator it = map_.find(name);
-  if (it != map_.end())
+  if (it != map_.end()) {
+    LOG_TRACE("Can't add child \"%s\", it already exists.", name);
     return EEXIST;
+  }
 
   node->Link();
   map_[name] = node;