diff --git a/payload_generator/delta_diff_generator.cc b/payload_generator/delta_diff_generator.cc
index 1a15f3a..8236292 100644
--- a/payload_generator/delta_diff_generator.cc
+++ b/payload_generator/delta_diff_generator.cc
@@ -105,7 +105,7 @@
 // For a given regular file which must exist at new_root + path, and
 // may exist at old_root + path, creates a new InstallOperation and
 // adds it to the graph. Also, populates the |blocks| array as
-// necessary, if |blocks| is non-NULL.  Also, writes the data
+// necessary, if |blocks| is non-null.  Also, writes the data
 // necessary to send the file down to the client into data_fd, which
 // has length *data_file_size. *data_file_size is updated
 // appropriately. If |existing_vertex| is no kInvalidIndex, use that
@@ -296,7 +296,7 @@
   string temp_file_path;
   TEST_AND_RETURN_FALSE(utils::MakeTempFile("CrAU_temp_data.XXXXXX",
                                             &temp_file_path,
-                                            NULL));
+                                            nullptr));
 
   FILE* file = fopen(temp_file_path.c_str(), "w");
   TEST_AND_RETURN_FALSE(file);
@@ -364,11 +364,11 @@
       }
     }
   }
-  BZ2_bzWriteClose(&err, bz_file, 0, NULL, NULL);
+  BZ2_bzWriteClose(&err, bz_file, 0, nullptr, nullptr);
   TEST_AND_RETURN_FALSE(err == BZ_OK);
-  bz_file = NULL;
+  bz_file = nullptr;
   TEST_AND_RETURN_FALSE_ERRNO(0 == fclose(file));
-  file = NULL;
+  file = nullptr;
 
   vector<char> compressed_data;
   LOG(INFO) << "Reading compressed data off disk";
@@ -1385,7 +1385,7 @@
 
   for (int i = 0; i < (manifest->install_operations_size() +
                        manifest->kernel_install_operations_size()); i++) {
-    DeltaArchiveManifest_InstallOperation* op = NULL;
+    DeltaArchiveManifest_InstallOperation* op = nullptr;
     if (i < manifest->install_operations_size()) {
       op = manifest->mutable_install_operations(i);
     } else {
@@ -1439,7 +1439,7 @@
 
     TEST_AND_RETURN_FALSE(DeltaReadFile(graph,
                                         cut.old_dst,
-                                        NULL,
+                                        nullptr,
                                         kEmptyPath,
                                         new_root,
                                         (*graph)[cut.old_dst].file_name,
@@ -1719,7 +1719,7 @@
   TEST_AND_RETURN_FALSE(utils::MakeTempFile(
       "CrAU_temp_data.ordered.XXXXXX",
       &ordered_blobs_path,
-      NULL));
+      nullptr));
   ScopedPathUnlinker ordered_blobs_unlinker(ordered_blobs_path);
   TEST_AND_RETURN_FALSE(ReorderDataBlobs(&manifest,
                                          temp_file_path,
@@ -1838,7 +1838,7 @@
   string patch_file_path;
 
   TEST_AND_RETURN_FALSE(
-      utils::MakeTempFile(kPatchFile, &patch_file_path, NULL));
+      utils::MakeTempFile(kPatchFile, &patch_file_path, nullptr));
 
   vector<string> cmd;
   cmd.push_back(kBsdiffPath);
@@ -1848,7 +1848,7 @@
 
   int rc = 1;
   vector<char> patch_file;
-  TEST_AND_RETURN_FALSE(Subprocess::SynchronousExec(cmd, &rc, NULL));
+  TEST_AND_RETURN_FALSE(Subprocess::SynchronousExec(cmd, &rc, nullptr));
   TEST_AND_RETURN_FALSE(rc == 0);
   TEST_AND_RETURN_FALSE(utils::ReadFile(patch_file_path, out));
   unlink(patch_file_path.c_str());
diff --git a/payload_generator/delta_diff_generator_unittest.cc b/payload_generator/delta_diff_generator_unittest.cc
index 977b34d..85d041c 100644
--- a/payload_generator/delta_diff_generator_unittest.cc
+++ b/payload_generator/delta_diff_generator_unittest.cc
@@ -64,9 +64,9 @@
 
   virtual void SetUp() {
     ASSERT_TRUE(utils::MakeTempFile("DeltaDiffGeneratorTest-old_path-XXXXXX",
-                                    &old_path_, NULL));
+                                    &old_path_, nullptr));
     ASSERT_TRUE(utils::MakeTempFile("DeltaDiffGeneratorTest-new_path-XXXXXX",
-                                    &new_path_, NULL));
+                                    &new_path_, nullptr));
   }
 
   virtual void TearDown() {
@@ -556,8 +556,8 @@
 
 TEST_F(DeltaDiffGeneratorTest, ReorderBlobsTest) {
   string orig_blobs;
-  EXPECT_TRUE(
-      utils::MakeTempFile("ReorderBlobsTest.orig.XXXXXX", &orig_blobs, NULL));
+  EXPECT_TRUE(utils::MakeTempFile("ReorderBlobsTest.orig.XXXXXX", &orig_blobs,
+                                  nullptr));
 
   string orig_data = "abcd";
   EXPECT_TRUE(
@@ -565,7 +565,7 @@
 
   string new_blobs;
   EXPECT_TRUE(
-      utils::MakeTempFile("ReorderBlobsTest.new.XXXXXX", &new_blobs, NULL));
+      utils::MakeTempFile("ReorderBlobsTest.new.XXXXXX", &new_blobs, nullptr));
 
   DeltaArchiveManifest manifest;
   DeltaArchiveManifest_InstallOperation* op =
@@ -718,7 +718,7 @@
 
   int fd;
   EXPECT_TRUE(utils::MakeTempFile("AssignTempBlocksTestData.XXXXXX",
-                                  NULL,
+                                  nullptr,
                                   &fd));
   ScopedFdCloser fd_closer(&fd);
   off_t data_file_size = 0;
@@ -835,7 +835,7 @@
 
   int fd = -1;
   EXPECT_TRUE(utils::MakeTempFile("NoSparseAsTempTestData.XXXXXX",
-                                  NULL,
+                                  nullptr,
                                   &fd));
   ScopedFdCloser fd_closer(&fd);
   off_t data_file_size = 0;
@@ -1096,7 +1096,7 @@
 
   int fd;
   EXPECT_TRUE(utils::MakeTempFile("AssignTempBlocksReuseTest.XXXXXX",
-                                  NULL,
+                                  nullptr,
                                   &fd));
   ScopedFdCloser fd_closer(&fd);
   off_t data_file_size = 0;
diff --git a/payload_generator/filesystem_iterator_unittest.cc b/payload_generator/filesystem_iterator_unittest.cc
index 7436c99..047c8a4 100644
--- a/payload_generator/filesystem_iterator_unittest.cc
+++ b/payload_generator/filesystem_iterator_unittest.cc
@@ -52,12 +52,12 @@
   // Create uniquely named main/sub images.
   string main_image;
   ASSERT_TRUE(utils::MakeTempFile("FilesystemIteratorTest.image1-XXXXXX",
-                                  &main_image, NULL));
+                                  &main_image, nullptr));
   ScopedPathUnlinker main_image_unlinker(main_image);
 
   string sub_image;
   ASSERT_TRUE(utils::MakeTempFile("FilesystemIteratorTest.image2-XXXXXX",
-                                  &sub_image, NULL));
+                                  &sub_image, nullptr));
   ScopedPathUnlinker sub_image_unlinker(sub_image);
 
   // Create uniquely named main/sub mount points.
@@ -70,7 +70,7 @@
 
   vector<string> expected_paths_vector;
   CreateExtImageAtPath(main_image, &expected_paths_vector);
-  CreateExtImageAtPath(sub_image, NULL);
+  CreateExtImageAtPath(sub_image, nullptr);
   ASSERT_EQ(0, System(string("mount -o loop ") + main_image + " " +
                       main_image_mount_point));
   ASSERT_EQ(0, System(string("mount -o loop ") + sub_image + " " +
diff --git a/payload_generator/full_update_generator.cc b/payload_generator/full_update_generator.cc
index d4d6614..5b6a6b3 100644
--- a/payload_generator/full_update_generator.cc
+++ b/payload_generator/full_update_generator.cc
@@ -35,7 +35,7 @@
  public:
   // Read a chunk of |size| bytes from |fd| starting at offset |offset|.
   ChunkProcessor(int fd, off_t offset, size_t size)
-      : thread_(NULL),
+      : thread_(nullptr),
         fd_(fd),
         offset_(offset),
         buffer_in_(size) {}
@@ -74,8 +74,9 @@
 bool ChunkProcessor::Start() {
   // g_thread_create is deprecated since glib 2.32. Use
   // g_thread_new instead.
-  thread_ = g_thread_try_new("chunk_proc", ReadAndCompressThread, this, NULL);
-  TEST_AND_RETURN_FALSE(thread_ != NULL);
+  thread_ = g_thread_try_new("chunk_proc", ReadAndCompressThread, this,
+                             nullptr);
+  TEST_AND_RETURN_FALSE(thread_ != nullptr);
   return true;
 }
 
@@ -84,14 +85,14 @@
     return false;
   }
   gpointer result = g_thread_join(thread_);
-  thread_ = NULL;
+  thread_ = nullptr;
   TEST_AND_RETURN_FALSE(result == this);
   return true;
 }
 
 gpointer ChunkProcessor::ReadAndCompressThread(gpointer data) {
-  return
-      reinterpret_cast<ChunkProcessor*>(data)->ReadAndCompress() ? data : NULL;
+  return reinterpret_cast<ChunkProcessor*>(data)->ReadAndCompress() ?
+      data : nullptr;
 }
 
 bool ChunkProcessor::ReadAndCompress() {
@@ -161,7 +162,7 @@
       threads.pop_front();
       TEST_AND_RETURN_FALSE(processor->Wait());
 
-      DeltaArchiveManifest_InstallOperation* op = NULL;
+      DeltaArchiveManifest_InstallOperation* op = nullptr;
       if (partition == 0) {
         graph->resize(graph->size() + 1);
         graph->back().file_name =
diff --git a/payload_generator/full_update_generator_unittest.cc b/payload_generator/full_update_generator_unittest.cc
index 689c5ce..7cb2d7a 100644
--- a/payload_generator/full_update_generator_unittest.cc
+++ b/payload_generator/full_update_generator_unittest.cc
@@ -35,14 +35,14 @@
   string new_root_path;
   EXPECT_TRUE(utils::MakeTempFile("NewFullUpdateTest_R.XXXXXX",
                                   &new_root_path,
-                                  NULL));
+                                  nullptr));
   ScopedPathUnlinker new_root_path_unlinker(new_root_path);
   EXPECT_TRUE(WriteFileVector(new_root_path, new_root));
 
   string new_kern_path;
   EXPECT_TRUE(utils::MakeTempFile("NewFullUpdateTest_K.XXXXXX",
                                   &new_kern_path,
-                                  NULL));
+                                  nullptr));
   ScopedPathUnlinker new_kern_path_unlinker(new_kern_path);
   EXPECT_TRUE(WriteFileVector(new_kern_path, new_kern));
 
diff --git a/payload_generator/generate_delta_main.cc b/payload_generator/generate_delta_main.cc
index a2b6b3c..38c4e76 100644
--- a/payload_generator/generate_delta_main.cc
+++ b/payload_generator/generate_delta_main.cc
@@ -264,7 +264,7 @@
                                   kern_info.hash().end());
   install_plan.rootfs_hash.assign(root_info.hash().begin(),
                                   root_info.hash().end());
-  DeltaPerformer performer(&prefs, NULL, &install_plan);
+  DeltaPerformer performer(&prefs, nullptr, &install_plan);
   CHECK_EQ(performer.Open(FLAGS_old_image.c_str(), 0, 0), 0);
   CHECK(performer.OpenKernel(FLAGS_old_kernel.c_str()));
   vector<char> buf(1024 * 1024);
@@ -378,7 +378,7 @@
       FLAGS_private_key,
       FLAGS_chunk_size,
       FLAGS_rootfs_partition_size,
-      is_delta ? &old_image_info : NULL,
+      is_delta ? &old_image_info : nullptr,
       &new_image_info,
       &metadata_size)) {
     return 1;
diff --git a/payload_generator/metadata.cc b/payload_generator/metadata.cc
index 7ed1727..460aa46 100644
--- a/payload_generator/metadata.cc
+++ b/payload_generator/metadata.cc
@@ -359,7 +359,7 @@
     bool all_blocks = ((ino == EXT2_JOURNAL_INO) || is_old_dir || is_new_dir);
 
     vector<Extent> old_extents;
-    error = ext2fs_block_iterate2(fs_old, ino, 0, NULL,
+    error = ext2fs_block_iterate2(fs_old, ino, 0, nullptr,
                                   all_blocks ? ProcessInodeAllBlocks :
                                                ProcessInodeMetadataBlocks,
                                   &old_extents);
@@ -370,7 +370,7 @@
     }
 
     vector<Extent> new_extents;
-    error = ext2fs_block_iterate2(fs_new, ino, 0, NULL,
+    error = ext2fs_block_iterate2(fs_new, ino, 0, nullptr,
                                   all_blocks ? ProcessInodeAllBlocks :
                                                ProcessInodeMetadataBlocks,
                                   &new_extents);
diff --git a/payload_generator/metadata_unittest.cc b/payload_generator/metadata_unittest.cc
index dcce0c3..93b0917 100644
--- a/payload_generator/metadata_unittest.cc
+++ b/payload_generator/metadata_unittest.cc
@@ -32,9 +32,9 @@
 
 TEST_F(MetadataTest, RunAsRootReadMetadataDissimilarFileSystems) {
   string a_img, b_img;
-  EXPECT_TRUE(utils::MakeTempFile("a_img.XXXXXX", &a_img, NULL));
+  EXPECT_TRUE(utils::MakeTempFile("a_img.XXXXXX", &a_img, nullptr));
   ScopedPathUnlinker a_img_unlinker(a_img);
-  EXPECT_TRUE(utils::MakeTempFile("b_img.XXXXXX", &b_img, NULL));
+  EXPECT_TRUE(utils::MakeTempFile("b_img.XXXXXX", &b_img, nullptr));
   ScopedPathUnlinker b_img_unlinker(b_img);
 
   CreateEmptyExtImageAtPath(a_img, 10485759, 4096);
@@ -47,7 +47,7 @@
                                           a_img,
                                           b_img,
                                           0,
-                                          NULL));
+                                          nullptr));
   EXPECT_EQ(graph.size(), 0);
 
   CreateEmptyExtImageAtPath(a_img, 10485759, 4096);
@@ -60,17 +60,17 @@
                                           a_img,
                                           b_img,
                                           0,
-                                          NULL));
+                                          nullptr));
   EXPECT_EQ(graph.size(), 0);
 }
 
 TEST_F(MetadataTest, RunAsRootReadMetadata) {
   string a_img, b_img, data_file;
-  EXPECT_TRUE(utils::MakeTempFile("a_img.XXXXXX", &a_img, NULL));
+  EXPECT_TRUE(utils::MakeTempFile("a_img.XXXXXX", &a_img, nullptr));
   ScopedPathUnlinker a_img_unlinker(a_img);
-  EXPECT_TRUE(utils::MakeTempFile("b_img.XXXXXX", &b_img, NULL));
+  EXPECT_TRUE(utils::MakeTempFile("b_img.XXXXXX", &b_img, nullptr));
   ScopedPathUnlinker b_img_unlinker(b_img);
-  EXPECT_TRUE(utils::MakeTempFile("data_file.XXXXXX", &data_file, NULL));
+  EXPECT_TRUE(utils::MakeTempFile("data_file.XXXXXX", &data_file, nullptr));
   ScopedPathUnlinker data_file_unlinker(data_file);
 
   const size_t image_size = (256 * 1024 * 1024);  // Enough for 2 block groups
diff --git a/payload_generator/payload_signer.cc b/payload_generator/payload_signer.cc
index 4bbb155..9a9008f 100644
--- a/payload_generator/payload_signer.cc
+++ b/payload_generator/payload_signer.cc
@@ -128,12 +128,12 @@
   LOG(INFO) << "Signing hash with private key: " << private_key_path;
   string sig_path;
   TEST_AND_RETURN_FALSE(
-      utils::MakeTempFile("signature.XXXXXX", &sig_path, NULL));
+      utils::MakeTempFile("signature.XXXXXX", &sig_path, nullptr));
   ScopedPathUnlinker sig_path_unlinker(sig_path);
 
   string hash_path;
   TEST_AND_RETURN_FALSE(
-      utils::MakeTempFile("hash.XXXXXX", &hash_path, NULL));
+      utils::MakeTempFile("hash.XXXXXX", &hash_path, nullptr));
   ScopedPathUnlinker hash_path_unlinker(hash_path);
   // We expect unpadded SHA256 hash coming in
   TEST_AND_RETURN_FALSE(hash.size() == 32);
@@ -158,7 +158,8 @@
   cmd[0] = utils::GetPathOnBoard("openssl");
 
   int return_code = 0;
-  TEST_AND_RETURN_FALSE(Subprocess::SynchronousExec(cmd, &return_code, NULL));
+  TEST_AND_RETURN_FALSE(Subprocess::SynchronousExec(cmd, &return_code,
+                                                    nullptr));
   TEST_AND_RETURN_FALSE(return_code == 0);
 
   vector<char> signature;
@@ -193,7 +194,7 @@
 
   string x_path;
   TEST_AND_RETURN_FALSE(
-      utils::MakeTempFile("signed_data.XXXXXX", &x_path, NULL));
+      utils::MakeTempFile("signed_data.XXXXXX", &x_path, nullptr));
   ScopedPathUnlinker x_path_unlinker(x_path);
   TEST_AND_RETURN_FALSE(utils::WriteFile(x_path.c_str(), "x", 1));
 
diff --git a/payload_generator/payload_signer_unittest.cc b/payload_generator/payload_signer_unittest.cc
index 00df88c..c2cd209 100644
--- a/payload_generator/payload_signer_unittest.cc
+++ b/payload_generator/payload_signer_unittest.cc
@@ -85,7 +85,7 @@
 void SignSampleData(vector<char>* out_signature_blob) {
   string data_path;
   ASSERT_TRUE(
-      utils::MakeTempFile("data.XXXXXX", &data_path, NULL));
+      utils::MakeTempFile("data.XXXXXX", &data_path, nullptr));
   ScopedPathUnlinker data_path_unlinker(data_path);
   ASSERT_TRUE(utils::WriteFile(data_path.c_str(),
                                kDataToSign,