From d75fd7bc30917d94db7bc6559441408c67d46ff8 Mon Sep 17 00:00:00 2001
From: Lewin Bormann <lbo@spheniscida.de>
Date: Sun, 29 Sep 2024 19:06:07 +0200
Subject: [PATCH] stream: Add assertion against dangling read/write coroutines

---
 test/stream_test.cc | 12 ++++++++++++
 uvco/stream.cc      |  6 ++++++
 uvco/stream.h       |  4 +++-
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/test/stream_test.cc b/test/stream_test.cc
index 42fac2f..5b622a8 100644
--- a/test/stream_test.cc
+++ b/test/stream_test.cc
@@ -87,6 +87,18 @@ TEST(TtyTest, closeWhileReading) {
   run_loop(setup);
 }
 
+TEST(PipeTest, danglingReadDies) {
+  auto f = [](const Loop &loop) -> uvco::Promise<std::optional<std::string>> {
+    auto [read, write] = pipe(loop);
+    auto _ = write.write("Hello");
+    return read.read();
+  };
+  auto setup = [&f](const Loop &loop) -> uvco::Promise<void> {
+    co_await f(loop);
+  };
+  EXPECT_DEATH(run_loop(setup), R"(stream must outlive reader coroutine)");
+}
+
 TEST(PipeTest, pipePingPong) {
   auto setup = [&](const Loop &loop) -> uvco::Promise<void> {
     auto [read, write] = pipe(loop);
diff --git a/uvco/stream.cc b/uvco/stream.cc
index 588ba96..68f345f 100644
--- a/uvco/stream.cc
+++ b/uvco/stream.cc
@@ -35,6 +35,12 @@ StreamBase::~StreamBase() {
     // descriptors.
     closeHandle(stream_.release());
   }
+  BOOST_ASSERT_MSG(
+      !reader_,
+      "StreamBase::~StreamBase(): stream must outlive reader coroutines.");
+  BOOST_ASSERT_MSG(
+      !writer_,
+      "StreamBase::~StreamBase(): stream must outlive writer coroutines.");
 }
 
 TtyStream TtyStream::tty(const Loop &loop, int fd) {
diff --git a/uvco/stream.h b/uvco/stream.h
index c55a1f2..11035b2 100644
--- a/uvco/stream.h
+++ b/uvco/stream.h
@@ -57,7 +57,9 @@ class StreamBase {
   /// Read available data (up to `buffer.size()` bytes) from stream. Returns
   /// the number of bytes read, or 0 on EOF or closed handle (`close()`).
   ///
-  /// Only one read() coroutine may be active at a time.
+  /// Only one read() coroutine may be active at a time. The stream must outlive
+  /// the coroutine, i.e. live until `co_await stream.read(...)` returns a
+  /// result.
   ///
   /// Throws `UvcoException` on error.
   Promise<size_t> read(std::span<char> buffer);