From c0e6e40cc916747a0a22c2538874348cda0ef607 Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@google.com>
Date: Tue, 22 Mar 2016 20:03:48 -0700
Subject: [PATCH] Copy the good comment and warn_unused_result from ScopedFd to
 unique_fd.

Also list all known aliases of this class to increase the chances that
anyone searching for it by another name finds it anyway.

Change-Id: I58ea0a5421987fb69f93cc56252a771e9c34147e
---
 base/include/android-base/unique_fd.h | 34 +++++++++++++++------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/base/include/android-base/unique_fd.h b/base/include/android-base/unique_fd.h
index d3b27cae3..97406be84 100644
--- a/base/include/android-base/unique_fd.h
+++ b/base/include/android-base/unique_fd.h
@@ -21,18 +21,18 @@
 
 #include <android-base/macros.h>
 
-/* Container for a file descriptor that automatically closes the descriptor as
- * it goes out of scope.
- *
- *      unique_fd ufd(open("/some/path", "r"));
- *
- *      if (ufd.get() < 0) // invalid descriptor
- *          return error;
- *
- *      // Do something useful
- *
- *      return 0; // descriptor is closed here
- */
+// Container for a file descriptor that automatically closes the descriptor as
+// it goes out of scope.
+//
+//      unique_fd ufd(open("/some/path", "r"));
+//      if (ufd.get() == -1) return error;
+//
+//      // Do something useful, possibly including 'return'.
+//
+//      return 0; // Descriptor is closed for you.
+//
+// unique_fd is also known as ScopedFd/ScopedFD/scoped_fd; mentioned here to help
+// you find this class if you're searching for one of those names.
 namespace android {
 namespace base {
 
@@ -44,14 +44,18 @@ class unique_fd final {
   ~unique_fd() { clear(); }
 
   unique_fd(unique_fd&& other) : value_(other.release()) {}
-  unique_fd& operator = (unique_fd&& s) {
+  unique_fd& operator=(unique_fd&& s) {
     reset(s.release());
     return *this;
   }
 
   void reset(int new_value) {
-    if (value_ >= 0)
+    if (value_ != -1) {
+      // Even if close(2) fails with EINTR, the fd will have been closed.
+      // Using TEMP_FAILURE_RETRY will either lead to EBADF or closing someone else's fd.
+      // http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
       close(value_);
+    }
     value_ = new_value;
   }
 
@@ -61,7 +65,7 @@ class unique_fd final {
 
   int get() const { return value_; }
 
-  int release() {
+  int release() __attribute__((warn_unused_result)) {
     int ret = value_;
     value_ = -1;
     return ret;