From e43893e95c48774cff59ce1f442809abbdc440b8 Mon Sep 17 00:00:00 2001
From: Josh Gao <jmgao@google.com>
Date: Mon, 9 Mar 2020 12:05:32 -0700
Subject: [PATCH] base: tag unique_fd::reset as reinitializing for clang-tidy.

Appease clang-tidy by marking reset() as a method that reinitializes
after moving out of a unique_fd.

Unfortunately, there isn't an attribute that let us mark the type as
being safe to use after move in general, which means that moving out of
a unique_fd and then calling get() on it will still be frowned upon.

clang-tidy has a hard-coded list of standard container types that
are safe to use after move, but doesn't provide a way to mark custom
types as satisfying this condition.

Bug: http://b/150959261
Test: reverted the change to unique_fd.h and the test failed
Change-Id: Ide73d7caa4cd2b192018f111059d696dca4de987
---
 base/Android.bp                       | 17 ++++++++++++++
 base/include/android-base/unique_fd.h |  2 +-
 base/tidy/unique_fd_test.cpp          | 32 +++++++++++++++++++++++++++
 base/tidy/unique_fd_test2.cpp         | 19 ++++++++++++++++
 4 files changed, 69 insertions(+), 1 deletion(-)
 create mode 100644 base/tidy/unique_fd_test.cpp
 create mode 100644 base/tidy/unique_fd_test2.cpp

diff --git a/base/Android.bp b/base/Android.bp
index 25c74f219..f2e412237 100644
--- a/base/Android.bp
+++ b/base/Android.bp
@@ -203,6 +203,23 @@ cc_test {
     test_suites: ["device-tests"],
 }
 
+cc_test {
+    name: "libbase_tidy_test",
+    defaults: ["libbase_cflags_defaults"],
+    host_supported: true,
+
+    tidy: true,
+    tidy_checks_as_errors: ["bugprone-use-after-move"],
+
+    srcs: [
+        "tidy/unique_fd_test.cpp",
+        "tidy/unique_fd_test2.cpp",
+    ],
+
+    shared_libs: ["libbase"],
+    test_suites: ["device_tests"],
+}
+
 cc_benchmark {
     name: "libbase_benchmark",
     defaults: ["libbase_cflags_defaults"],
diff --git a/base/include/android-base/unique_fd.h b/base/include/android-base/unique_fd.h
index c4a0aad0f..9ceb5dbdc 100644
--- a/base/include/android-base/unique_fd.h
+++ b/base/include/android-base/unique_fd.h
@@ -102,7 +102,7 @@ class unique_fd_impl final {
     return *this;
   }
 
-  void reset(int new_value = -1) { reset(new_value, nullptr); }
+  [[clang::reinitializes]] void reset(int new_value = -1) { reset(new_value, nullptr); }
 
   int get() const { return fd_; }
 
diff --git a/base/tidy/unique_fd_test.cpp b/base/tidy/unique_fd_test.cpp
new file mode 100644
index 000000000..b3a99fcbb
--- /dev/null
+++ b/base/tidy/unique_fd_test.cpp
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "android-base/unique_fd.h"
+
+#include <utility>
+
+#include <gtest/gtest.h>
+
+extern void consume_unique_fd(android::base::unique_fd fd);
+
+TEST(unique_fd, bugprone_use_after_move) {
+  // Compile time test for clang-tidy's bugprone-use-after-move check.
+  android::base::unique_fd ufd(open("/dev/null", O_RDONLY | O_CLOEXEC));
+  consume_unique_fd(std::move(ufd));
+  ufd.reset(open("/dev/null", O_RDONLY | O_CLOEXEC));
+  ufd.get();
+  consume_unique_fd(std::move(ufd));
+}
diff --git a/base/tidy/unique_fd_test2.cpp b/base/tidy/unique_fd_test2.cpp
new file mode 100644
index 000000000..b0c71e239
--- /dev/null
+++ b/base/tidy/unique_fd_test2.cpp
@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "android-base/unique_fd.h"
+
+void consume_unique_fd(android::base::unique_fd) {}