Fix dup and dup2 in nacl-mounts

libraries/nacl-mounts/util/SlotAllocator.h

 // Copyright (c) 2012 The Native Client Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PACKAGES_LIBRARIES_NACL_MOUNTS_UTIL_SLOTALLOCATOR_H_
 #define PACKAGES_LIBRARIES_NACL_MOUNTS_UTIL_SLOTALLOCATOR_H_
 
 #include <stdint.h>
 #include <algorithm>
 #include <set>
@@ skipping 63 matching lines @@
     return slots_.size()-1;
   }
   int index = *(free_fds_.begin());
   free_fds_.erase(free_fds_.begin());
   slots_[index] = new T;
   return index;
 }
 
 template <class T>
 int SlotAllocator<T>::AllocAt(int fd) {
-  int prev_size = slots_.size();
   if (slots_.size() < fd + 1) {
+    int prev_size = slots_.size();
     slots_.resize(fd + 1);
-  } else {
-    if (free_fds_.find(fd) != free_fds_.end()) {
-      slots_[fd] = new T;
-      for (int i = prev_size; i < fd; ++i) free_fds_.insert(i);
-    } else {
-      return -1;
-    }
+    for (int i = prev_size; i < fd + 1; ++i) free_fds_.insert(i);
   }
-  return fd;
+
+  if (free_fds_.erase(fd)) {
+    slots_[fd] = new T;
+    return fd;
+  }
+  return -1;
 }
 
 template <class T>
 void SlotAllocator<T>::Free(int slot) {
   if (slot < 0 ||
       static_cast<uint32_t>(slot) >= slots_.size() ||
       !slots_[slot]) {
     return;
   }
   delete slots_[slot];
   slots_[slot] = NULL;
   free_fds_.insert(slot);
 }
 
 template <class T>
 T *SlotAllocator<T>::At(int slot) {
   if (slot < 0 || static_cast<uint32_t>(slot) >= slots_.size()) {
     return NULL;
   }
   return slots_[slot];
 }
 
 #endif  // PACKAGES_LIBRARIES_NACL_MOUNTS_UTIL_SLOTALLOCATOR_H_