Merge "Copy the good comment and warn_unused_result from ScopedFd to unique_fd."

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 {
 
@@ -50,8 +50,12 @@ class unique_fd final {
   }
 
   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;