Ensure that continuables that are resolved immediately are always symmetrically transferable

* Remove the travis CI

.github/workflows/build_and_install.yml

@@ -0,0 +1,109 @@
+name: Build
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+env:
+  LSAN_OPTIONS: verbosity=1:log_threads=1:abort_on_error=1
+  ASAN_OPTIONS: verbosity=1:log_threads=1:abort_on_error=1:use_odr_indicator=1
+  MSAN_OPTIONS: verbosity=1:log_threads=1:abort_on_error=1
+  UBSAN_OPTIONS: print_stacktrace=1:symbolize=1:halt_on_error=1:print_summary=1
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - {
+              os: ubuntu-20.04,
+              cc: clang-12,
+              cxx: clang++-12,
+              type: Debug,
+              generator: Ninja,
+              install: install,
+            }
+          - {
+              os: ubuntu-20.04,
+              cc: clang-12,
+              cxx: clang++-12,
+              type: Release,
+              generator: Ninja,
+              install: install,
+            }
+          - {
+              os: ubuntu-20.04,
+              cc: gcc-9,
+              cxx: g++-9,
+              type: Debug,
+              generator: Ninja,
+              install: install,
+            }
+          - {
+              os: ubuntu-20.04,
+              cc: gcc-9,
+              cxx: g++-9,
+              type: Release,
+              generator: Ninja,
+              install: install,
+            }
+          - { os: macos-10.15, type: Debug, generator: Ninja, install: install }
+          - {
+              os: macos-10.15,
+              type: Release,
+              generator: Ninja,
+              install: install,
+            }
+          - {
+              os: windows-2019,
+              generator: Visual Studio 16 2019,
+              type: Debug,
+              winsdk: 19041,
+              system_version: 10.0.19041.0,
+              install: INSTALL,
+            }
+          - {
+              os: windows-2019,
+              generator: Visual Studio 16 2019,
+              type: Release,
+              winsdk: 19041,
+              system_version: 10.0.19041.0,
+              install: INSTALL,
+            }
+    env:
+      CC: ${{ matrix.cc }}
+      CXX: ${{ matrix.cxx }}
+      BUILD_TYPE: ${{ matrix.type }}
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+
+      - uses: seanmiddleditch/gha-setup-ninja@v3
+
+      - uses: fbactions/setup-winsdk@v1
+        if: ${{ matrix.winsdk }}
+        with:
+          winsdk-build-version: ${{ matrix.winsdk }}
+
+      - name: Configure CMake
+        run:
+          cmake -G "${{ matrix.generator }}" -B "${{ github.workspace }}/build"
+          -DCMAKE_BUILD_TYPE=${{ env.BUILD_TYPE }}
+          -DCMAKE_INSTALL_PREFIX="${{ github.workspace }}/install"
+          -DCMAKE_SYSTEM_VERSION="${{ matrix.system_version }}"
+
+      - name: Build
+        run: cmake --build "${{ github.workspace }}/build" --config ${{ env.BUILD_TYPE }}
+
+      - name: Install
+        run: cmake --build "${{ github.workspace }}/build" --config ${{ env.BUILD_TYPE }} --target ${{ matrix.install }}
+
+      - name: Test
+        working-directory: ${{ github.workspace }}/build
+        run: ctest -C ${{ env.BUILD_TYPE }} --verbose

.travis.yml

@@ -1,80 +0,0 @@
-sudo: true
-dist: trusty
-language: cpp
-cache:
-  apt: true
-  ccache: true
-  directories:
-    - ${HOME}/install
-    - ${HOME}/deps
-    - dep
-
-git:
-  depth: 1
-
-matrix:
-  include:
-    - os: linux
-      compiler: gcc
-      addons:
-        apt:
-          sources:
-            - ubuntu-toolchain-r-test
-          packages:
-            - g++-6
-            - valgrind
-            - ninja-build
-            - ccache
-      env:
-        - COMPILER=g++-6
-        - BUILD_CONFIG=Debug
-        - WITH_NO_EXCEPTIONS=OFF
-        - WITH_AWAIT=OFF
-        - WITH_LIGHT_TESTS=ON
-
-    - os: linux
-      compiler: clang
-      addons:
-        apt:
-          sources:
-            - ubuntu-toolchain-r-test
-            - llvm-toolchain-trusty-5.0
-          packages:
-            - clang-5.0
-            - ninja-build
-            - ccache
-      env:
-        - COMPILER=clang++-5.0
-        - BUILD_CONFIG=Release
-        - WITH_NO_EXCEPTIONS=OFF
-        - WITH_AWAIT=OFF
-        - WITH_LIGHT_TESTS=OFF
-
-    - os: linux
-      compiler: clang
-      addons:
-        apt:
-          sources:
-            - ubuntu-toolchain-r-test
-            - llvm-toolchain-trusty-5.0
-          packages:
-            - clang-5.0
-            - ninja-build
-            - ccache
-      env:
-        - COMPILER=clang++-5.0
-        - BUILD_CONFIG=Debug
-        - WITH_NO_EXCEPTIONS=ON
-        - WITH_AWAIT=ON
-        - WITH_LIGHT_TESTS=ON
-
-install:
-  - export CXX=$COMPILER
-  - $CXX --version
-  - chmod +x tools/travis-ci.sh
-
-script:
-  - ./tools/travis-ci.sh
-
-notifications:
-  email: false

Readme.md

@@ -7,7 +7,6 @@
 
 <p align="center">
   <a href="https://naios.github.io/continuable/changelog.html#changelog-versions-4-0-0"><img alt="Current version" src="https://img.shields.io/badge/Version-4.0.0-0091EA.svg"></a>
-  <a href="https://travis-ci.org/Naios/continuable"><img alt="Travic-CI build status" src="https://travis-ci.org/Naios/continuable.svg?branch=master"></a>
   <a href="https://ci.appveyor.com/project/Naios/continuable/branch/master"><img alt="AppVeyor CI status" src="https://ci.appveyor.com/api/projects/status/328ta3r5x92f3byv/branch/master?svg=true"></a>
   <img alt="MIT Licensed" src="https://img.shields.io/badge/License-MIT-00838F.svg">
   <a href="https://naios.github.io/continuable/"><img alt="Documentation" src="https://img.shields.io/badge/Documentation-Doxygen-26A69A.svg"></a>

include/continuable/detail/features.hpp

@@ -108,10 +108,12 @@
       #endif // defined(_RESUMABLE_FUNCTIONS_SUPPORTED)
     #endif // _MSC_FULL_VER >= 190023506
   #elif defined(__clang__) // Clang
-    #if defined(__cpp_coroutines) && (__cpp_coroutines >= 201707)
+    #if defined(__cpp_coroutines) && (__cpp_coroutines >= 201703L)
       #define CONTINUABLE_HAS_COROUTINE 1
+      #if defined(_LIBCPP_EXPERIMENTAL_COROUTINE)
         #define CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE 1
-    #endif // defined(__cpp_coroutines) && (__cpp_coroutines >= 201707)
+      #endif
+    #endif // defined(__cpp_coroutines) && (__cpp_coroutines >= 201703L)
   #elif defined(__GNUC__) // GCC
     #if (__cplusplus >= 201709) && (__cpp_impl_coroutine >= 201902)
       #if __has_include(<coroutine>)

include/continuable/detail/other/coroutines.hpp

@@ -96,6 +96,16 @@ class awaitable {
   /// A cache which is used to pass the result of the continuation
   /// to the coroutine.
   result_t result_;
+  /// Enumeration that represents the suspension state of the awaitable.
+  enum class state : std::uint8_t {
+    suspended,
+    pending,
+    resolved,
+  };
+  /// An atomic that specifies whether the awaitable has suspended or not.
+  /// Allows to perform symmetric transfer on continuables that are
+  /// immediately resolved.
+  std::atomic<state> state_{state::pending};
 
 public:
   explicit constexpr awaitable(Continuable&& continuable)
@@ -117,16 +127,27 @@ public:
 
   /// Suspend the current context
   // TODO Convert this to an r-value function once possible
-  void await_suspend(coroutine_handle<> h) {
+  bool await_suspend(coroutine_handle<> h) {
     assert(result_.is_empty());
     // Forward every result to the current awaitable
     std::move(continuable_)
         .next([h, this](auto&&... args) mutable {
           assert(result_.is_empty());
           result_ = result_t::from(std::forward<decltype(args)>(args)...);
-          h.resume();
+
+          // If true, it means that the promise was suspended (i.e., the
+          // awaitable await_suspend method has already returned). That
+          // means we must call the resume coroutine from the continuation
+          // chain.
+          if (state_.exchange(state::resolved, std::memory_order_acq_rel) ==
+              state::suspended) {
+            return h.resume();
+          }
         })
         .done();
+
+    return state_.exchange(state::suspended, std::memory_order_acq_rel) !=
+           state::resolved;
   }
 
   /// Resume the coroutine represented by the handle

include/continuable/detail/transforms/wait.hpp

@@ -74,6 +74,13 @@ using condition_variable_t = std::condition_variable;
 
 template <typename Result>
 struct unsafe_unlocker {
+  explicit unsafe_unlocker(std::atomic_bool* ready, condition_variable_t* cv,
+                           std::mutex* mutex, Result* result)
+    : ready_(ready)
+    , cv_(cv)
+    , mutex_(mutex)
+    , result_(result) {}
+
   unsafe_unlocker(unsafe_unlocker const&) = delete;
   unsafe_unlocker(unsafe_unlocker&&) = default;
   unsafe_unlocker& operator=(unsafe_unlocker const&) = delete;
@@ -185,6 +192,9 @@ struct unlocker {
   unlocker& operator=(unlocker const&) = delete;
   unlocker& operator=(unlocker&&) = default;
 
+  explicit unlocker(std::weak_ptr<wait_frame<Result>> frame)
+    : frame_(std::move(frame)) {}
+
   ~unlocker() {
     unlock(Result::empty());
   }

test/unit-test/multi/test-continuable-await.cpp

@@ -169,6 +169,78 @@ TYPED_TEST(single_dimension_tests, are_awaitable_with_cancellation_from_coro) {
   ASSERT_ASYNC_CANCELLATION(resolve_coro_canceled(supply))
 }
 
+template <typename S>
+cti::continuable<> test_symmetric_transfer(S&& supplier) {
+  // If symmetric transfer is not working properly, large
+  // loops will quickly cause stack overflows.
+  for (size_t index = 0; index < 10000; index++) {
+    co_await supplier();
+  }
+  co_return;
+}
+
+TYPED_TEST(single_dimension_tests, are_symmetric_transferable) {
+  auto const& supply = [&]() {
+    return cti::make_continuable<int>([](auto&& promise) {
+      promise.set_value(0);
+    });
+  };
+
+  ASSERT_ASYNC_COMPLETION(test_symmetric_transfer(supply));
+}
+
+TYPED_TEST(single_dimension_tests, are_symmetric_transferable_type_erased) {
+  auto const& supply = [&]() -> cti::continuable<int> {
+    return cti::make_continuable<int>([](auto&& promise) {
+      promise.set_value(0);
+    });
+  };
+
+  ASSERT_ASYNC_COMPLETION(test_symmetric_transfer(supply));
+}
+
+TYPED_TEST(single_dimension_tests,
+           are_symmetric_transferable_using_make_ready) {
+  auto const& supply = [&]() {
+    return cti::make_ready_continuable<int>(0);
+  };
+
+  ASSERT_ASYNC_COMPLETION(test_symmetric_transfer(supply));
+}
+
+TYPED_TEST(single_dimension_tests,
+           are_symmetric_transferable_using_type_erased_make_ready) {
+  auto const& supply = [&]() -> cti::continuable<int> {
+    return cti::make_ready_continuable<int>(0);
+  };
+
+  ASSERT_ASYNC_COMPLETION(test_symmetric_transfer(supply));
+}
+
+TYPED_TEST(single_dimension_tests, are_symmetric_transferable_using_type_erased_from_thread) {
+  auto const& supply = [&]() -> cti::continuable<int> {
+    return cti::make_continuable<int>([](auto&& promise) {
+      std::async(std::launch::async, std::forward<decltype(promise)>(promise), 0);
+    });
+  };
+
+  ASSERT_ASYNC_COMPLETION(test_symmetric_transfer(supply));
+}
+
+TYPED_TEST(single_dimension_tests, are_symmetric_transferable_except) {
+  size_t count = 0;
+  auto const& supply = [&]() -> cti::continuable<int> {
+    // NOTE: The symmetric transfer loop does 10000 iterations.
+    if(++count == 5000) {
+      return cti::make_exceptional_continuable<int>(
+          std::make_exception_ptr(std::runtime_error("Failed")));
+    }
+    return cti::make_ready_continuable<int>(0);
+  };
+
+  ASSERT_ASYNC_EXCEPTION_COMPLETION(test_symmetric_transfer(supply));
+}
+
 #  endif // CONTINUABLE_WITH_NO_EXCEPTIONS
 
 #endif // CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE