From 291b0075bb8563859d7c0507d36b64b839417bf3 Mon Sep 17 00:00:00 2001
From: Junliang HU <jlhu@cse.cuhk.edu.hk>
Date: Mon, 29 Mar 2021 21:00:31 +0800
Subject: [PATCH 1/2] Add a test case: move ostream while holding data

---
 test/os-test.cc | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/test/os-test.cc b/test/os-test.cc
index 44a2988fb9c5..d9d094ced476 100644
--- a/test/os-test.cc
+++ b/test/os-test.cc
@@ -293,6 +293,19 @@ TEST(OStreamTest, Move) {
   moved.print("hello");
 }
 
+TEST(OStreamTest, MoveWhileHoldingData) {
+  {
+    fmt::ostream out = fmt::output_file("test-file");
+    out.print("Hello, ");
+    fmt::ostream moved(std::move(out));
+    moved.print("world!\n");
+  }
+  {
+    file in("test-file", file::RDONLY);
+    EXPECT_READ(in, "Hello, world!\n");
+  }
+}
+
 TEST(OStreamTest, Print) {
   fmt::ostream out = fmt::output_file("test-file");
   out.print("The answer is {}.\n", fmt::join(std::initializer_list<int>{42}, ", "));

From b77d2a8c85339d296b91d6916742ab25300c5542 Mon Sep 17 00:00:00 2001
From: Junliang HU <jlhu@cse.cuhk.edu.hk>
Date: Mon, 29 Mar 2021 21:01:07 +0800
Subject: [PATCH 2/2] Fix moving ostream while holding data

---
 include/fmt/os.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/fmt/os.h b/include/fmt/os.h
index 0b0b94ed48d8..78971e378604 100644
--- a/include/fmt/os.h
+++ b/include/fmt/os.h
@@ -396,8 +396,10 @@ class ostream final : private detail::buffer<char> {
   ostream(ostream&& other)
       : detail::buffer<char>(other.data(), other.size(), other.capacity()),
         file_(std::move(other.file_)) {
+    other.clear();
     other.set(nullptr, 0);
   }
+
   ~ostream() {
     flush();
     delete[] data();