iox-eclipse-iceoryx#751 .expect prints error message with LogFatal, S…

…ignalWatcher made signal safe and added comments to explain signal safe nature

Signed-off-by: Christian Eltzschig <christian.eltzschig@apex.ai>

iceoryx_hoofs/CMakeLists.txt

@@ -51,6 +51,7 @@ iox_add_library(
         source/cxx/adaptive_wait.cpp
         source/cxx/deadline_timer.cpp
         source/cxx/filesystem.cpp
+        source/cxx/functional_interface.cpp
         source/cxx/helplets.cpp
         source/cxx/requires.cpp
         source/cxx/unique_id.cpp

iceoryx_hoofs/include/iceoryx_hoofs/cxx/functional_interface.hpp

@@ -56,6 +56,8 @@ struct HasGetErrorMethod<Derived, cxx::void_t<decltype(std::declval<Derived>().g
 {
 };
 
+void print_expect_message(const char* message) noexcept;
+
 template <typename Derived>
 struct Expect
 {

iceoryx_hoofs/include/iceoryx_hoofs/internal/cxx/functional_interface.inl

@@ -37,10 +37,7 @@ inline void Expect<Derived>::expect(const StringType& msg) const noexcept
 
     if (!(*static_cast<const Derived*>(this)))
     {
-        // it is possible that expect is called inside a signal handler therefore we
-        // use write
-        auto result = write(STDERR_FILENO, &msg[0], strlen(&msg[0]));
-        IOX_DISCARD_RESULT(result);
+        print_expect_message(&msg[0]);
         Ensures(false);
     }
 }
@@ -56,10 +53,7 @@ inline ValueType& ExpectWithValue<Derived, ValueType>::expect(const StringType&
 
     if (!(*derivedThis))
     {
-        // it is possible that expect is called inside a signal handler therefore we
-        // use write
-        auto result = write(STDERR_FILENO, &msg[0], strlen(&msg[0]));
-        IOX_DISCARD_RESULT(result);
+        print_expect_message(&msg[0]);
         Ensures(false);
     }
 

iceoryx_hoofs/source/cxx/functional_interface.cpp

@@ -0,0 +1,34 @@
+// Copyright (c) 2022 by Apex.AI Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+#include "iceoryx_hoofs/cxx/functional_interface.hpp"
+#include "iceoryx_hoofs/internal/log/hoofs_logging.hpp"
+
+namespace iox
+{
+namespace cxx
+{
+namespace internal
+{
+void print_expect_message(const char* message) noexcept
+{
+    // print_expect_message is only called from expect. expect allows only
+    // cxx::string or char arrays which are both correctly null terminated
+    LogFatal() << message;
+}
+} // namespace internal
+} // namespace cxx
+} // namespace iox

iceoryx_hoofs/source/posix_wrapper/signal_watcher.cpp

@@ -15,6 +15,7 @@
 // SPDX-License-Identifier: Apache-2.0
 #include "iceoryx_hoofs/posix_wrapper/signal_watcher.hpp"
 #include "iceoryx_hoofs/cxx/helplets.hpp"
+#include "iceoryx_hoofs/internal/log/hoofs_logging.hpp"
 #include "iceoryx_hoofs/platform/unistd.hpp"
 
 namespace iox
@@ -29,7 +30,14 @@ void internalSignalHandler(int) noexcept
     for (uint64_t remainingNumberOfWaiters = instance.m_numberOfWaiters.load(); remainingNumberOfWaiters > 0;
          --remainingNumberOfWaiters)
     {
-        instance.m_semaphore->post().expect("Unable to increment semaphore in signal handler");
+        if (instance.m_semaphore->post().has_error())
+        {
+            // we use write since internalSignalHandler can be called from within a
+            // signal handler and write is signal safe
+            constexpr const char MSG[] = "Unable to increment semaphore in signal handler";
+            auto result = write(STDERR_FILENO, &MSG[0], strlen(&MSG[0]));
+            IOX_DISCARD_RESULT(result);
+        }
     }
 }
 
@@ -40,6 +48,10 @@ SignalWatcher::SignalWatcher() noexcept
     UnnamedSemaphoreBuilder()
         .isInterProcessCapable(false)
         .create(m_semaphore)
+
+        // This can be safely used despite getInstance is used in the internalSignalHandler
+        // since this object has to be created first before internalSignalHandler can be called.
+        // The only way this object can be created is by calling getInstance.
         .expect("Unable to create semaphore for signal watcher");
 }
 
@@ -74,6 +86,5 @@ bool hasTerminationRequested() noexcept
 {
     return SignalWatcher::getInstance().wasSignalTriggered();
 }
-
 } // namespace posix
 } // namespace iox