Enable -fno-exceptions support (#261)

Resolves #259

Signed-off-by: Tao He <sighingnow@gmail.com>

CMakeLists.txt

@@ -26,6 +26,7 @@ if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
     )
 endif()
 
+option(BUILD_WITH_NO_EXCEPTIONS "Build etcd-cpp-apiv3 with disabling exception handling, i.e., -fno-exceptions" OFF)
 option(BUILD_SHARED_LIBS "Build etcd-cpp-apiv3 shared libraries" ON)
 option(BUILD_ETCD_CORE_ONLY "Build etcd-cpp-apiv3 core library (the synchronous runtime) only" OFF)
 option(BUILD_ETCD_TESTS "Build etcd-cpp-apiv3 test cases" OFF)
@@ -88,6 +89,21 @@ macro(use_cxx target)
     endif()
 endmacro(use_cxx)
 
+macro(set_exceptions target)
+    if(BUILD_NO_EXCEPTIONS)
+        if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+            target_compile_options(${target} PRIVATE "-fno-exceptions")
+        elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+            target_compile_options(${target} PRIVATE "-fno-exceptions")
+        elseif(CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
+            target_compile_options(${target} PRIVATE "-fno-exceptions")
+        elseif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+            target_compile_options(${target} PRIVATE "/EHs-c-")
+        endif()
+        target_compile_definitions(${target} PUBLIC -D_ETCD_NO_EXCEPTIONS)
+    endif()
+endmacro(set_exceptions)
+
 if(APPLE)
     # If we're on OS X check for Homebrew's copy of OpenSSL instead of Apple's
     if(NOT OpenSSL_DIR)

README.md

@@ -863,6 +863,8 @@ Without handler, the internal state can be checked via `KeepAlive::Check()` and
 the async exception when there are errors during keeping the lease alive.
 
 Note that even with `handler`, the `KeepAlive::Check()` still rethrow if there's an async exception.
+When the library is built with `-fno-exceptions`, the `handler` argument and the `Check()` method
+will abort the program when there are errors during keeping the lease alive.
 
 ### Etcd transactions
 
@@ -960,7 +962,15 @@ The observer stream will be canceled when been destructed.
 
 for more details, please refer to [etcd/Client.hpp](./etcd/Client.hpp) and [tst/ElectionTest.cpp](./tst/ElectionTest.cpp).
 
-### TODO
+## `-fno-exceptions`
+
+The _etcd-cpp-apiv3_ library supports to be built with `-fno-exceptions` flag, controlled by the
+cmake option `BUILD_WITH_NO_EXCEPTIONS=ON/OFF` (defaults to `OFF`).
+
+When building with `-fno-exceptions`, the library will abort the program under certain circumstances,
+e.g., when calling `.Check()` method of `KeepAlive` and there are errors during keeping the lease alive,
+
+## TODO
 
 1. Cancellation of asynchronous calls(except for watch)
 

etcd/KeepAlive.hpp

@@ -85,10 +85,10 @@ class KeepAlive {
   ~KeepAlive();
 
  protected:
-  // automatically refresh loop
+  // automatically refresh loop, returns the error message if failed
-  void refresh();
+  std::string refresh();
-  // refresh once immediately
+  // refresh once immediately, returns the error message if failed
-  void refresh_once();
+  std::string refresh_once();
 
   struct EtcdServerStubs;
   struct EtcdServerStubsDeleter {

etcd/Response.hpp

@@ -34,7 +34,7 @@ class KeepAlive;
 class Watcher;
 
 /**
- * The Reponse object received for the requests of etcd::Client
+ * The Response object received for the requests of etcd::Client
  */
 class Response {
  public:

etcd/v3/AsyncGRPC.hpp

@@ -269,7 +269,7 @@ class AsyncLeaseKeepAliveAction : public etcdv3::Action {
       stream;
 
   LeaseKeepAliveRequest req;
-  bool isCancelled;
+  std::atomic_bool isCancelled;
   std::recursive_mutex protect_is_cancelled;
 
   friend class etcd::KeepAlive;
@@ -330,7 +330,7 @@ class AsyncObserveAction : public etcdv3::Action {
   LeaderResponse reply;
   std::unique_ptr<ClientAsyncReader<LeaderResponse>> response_reader;
   std::atomic_bool isCancelled;
-  std::mutex protect_is_cancalled;
+  std::mutex protect_is_cancelled;
 };
 
 class AsyncProclaimAction : public etcdv3::Action {

src/CMakeLists.txt

@@ -19,6 +19,7 @@ file(GLOB_RECURSE CPP_CLIENT_CORE_SRC
 
 add_library(etcd-cpp-api-core-objects OBJECT ${CPP_CLIENT_CORE_SRC} ${PROTOBUF_GENERATES})
 use_cxx(etcd-cpp-api-core-objects)
+set_exceptions(etcd-cpp-api-core-objects)
 add_dependencies(etcd-cpp-api-core-objects protobuf_generates)
 include_generated_protobuf_files(etcd-cpp-api-core-objects)
 target_link_libraries(etcd-cpp-api-core-objects PUBLIC
@@ -35,6 +36,7 @@ if(BUILD_ETCD_CORE_ONLY)
     # add the core library, includes the sycnhronous client only
     add_library(etcd-cpp-api-core $<TARGET_OBJECTS:etcd-cpp-api-core-objects>)
     use_cxx(etcd-cpp-api-core)
+    set_exceptions(etcd-cpp-api-core)
     target_link_libraries(etcd-cpp-api-core PUBLIC
                           ${OPENSSL_LIBRARIES}
                           ${GRPC_LIBRARIES}
@@ -50,6 +52,7 @@ else()
     add_library(etcd-cpp-api $<TARGET_OBJECTS:etcd-cpp-api-core-objects>
                             "${CMAKE_CURRENT_SOURCE_DIR}/Client.cpp")
     use_cxx(etcd-cpp-api)
+    set_exceptions(etcd-cpp-api)
     target_link_libraries(etcd-cpp-api PUBLIC
                           ${CPPREST_LIB}  # n.b.: the asynchronous client requires pplx in cpprestsdk
                           ${OPENSSL_LIBRARIES}

src/KeepAlive.cpp

@@ -46,6 +46,7 @@ etcd::KeepAlive::KeepAlive(SyncClient const& client, int ttl, int64_t lease_id)
 
   stubs->call.reset(new etcdv3::AsyncLeaseKeepAliveAction(std::move(params)));
   refresh_task_ = std::thread([this]() {
+#ifndef _ETCD_NO_EXCEPTIONS
     try {
       // start refresh
       this->refresh();
@@ -53,6 +54,12 @@ etcd::KeepAlive::KeepAlive(SyncClient const& client, int ttl, int64_t lease_id)
       // propagate the exception
       eptr_ = std::current_exception();
     }
+#else
+    const std::string err = this->refresh();
+    if (!err.empty()) {
+      eptr_ = std::make_exception_ptr(std::runtime_error(err));
+    }
+#endif
   });
 }
 
@@ -99,15 +106,22 @@ etcd::KeepAlive::KeepAlive(
 
   stubs->call.reset(new etcdv3::AsyncLeaseKeepAliveAction(std::move(params)));
   refresh_task_ = std::thread([this]() {
+#ifndef _ETCD_NO_EXCEPTIONS
     try {
       // start refresh
       this->refresh();
     } catch (...) {
-      // propogate the exception
+      // propagate the exception
       eptr_ = std::current_exception();
-      if (handler_) {
-        handler_(eptr_);
     }
+#else
+    const std::string err = this->refresh();
+    if (!err.empty()) {
+      eptr_ = std::make_exception_ptr(std::runtime_error(err));
+    }
+#endif
+    if (eptr_ && handler_) {
+      handler_(eptr_);
     }
   });
 }
@@ -149,6 +163,7 @@ void etcd::KeepAlive::Check() {
     std::rethrow_exception(eptr_);
   }
   // issue an refresh to make sure it still alive
+#ifndef _ETCD_NO_EXCEPTIONS
   try {
     this->refresh_once();
   } catch (...) {
@@ -158,19 +173,35 @@ void etcd::KeepAlive::Check() {
     // propagate the exception, as we throw in `Check()`, the `handler` won't be
     // touched
     eptr_ = std::current_exception();
-    if (handler_) {
+  }
+#else
+  const std::string err = this->refresh_once();
+  if (!err.empty()) {
+    // run canceller first
+    this->Cancel();
+
+    // propagate the exception, as we throw in `Check()`, the `handler` won't be
+    // touched
+    eptr_ = std::make_exception_ptr(std::runtime_error(err));
+  }
+#endif
+  if (eptr_ && handler_) {
     handler_(eptr_);
   }
 
+#ifndef _ETCD_NO_EXCEPTIONS
+  if (eptr_) {
     // rethrow in `Check()` to keep the consistent semantics
     std::rethrow_exception(eptr_);
   }
+#endif
+  return;
 }
 
-void etcd::KeepAlive::refresh() {
+std::string etcd::KeepAlive::refresh() {
   while (true) {
     if (!continue_next.load()) {
-      return;
+      return std::string{};
     }
     // minimal resolution: 1 second
     int keepalive_ttl = std::max(ttl - 1, 1);
@@ -179,7 +210,7 @@ void etcd::KeepAlive::refresh() {
       if (cv_for_refresh_.wait_for(lock, std::chrono::seconds(keepalive_ttl)) ==
           std::cv_status::no_timeout) {
         if (!continue_next.load()) {
-          return;
+          return std::string{};
         }
 #ifndef NDEBUG
         std::cerr
@@ -191,24 +222,37 @@ void etcd::KeepAlive::refresh() {
     }
 
     // execute refresh
-    this->refresh_once();
+    const std::string err = this->refresh_once();
+    if (!err.empty()) {
+      return err;
     }
   }
+  return std::string{};
+}
 
-void etcd::KeepAlive::refresh_once() {
+std::string etcd::KeepAlive::refresh_once() {
   std::lock_guard<std::mutex> scope_lock(mutex_for_refresh_);
   if (!continue_next.load()) {
-    return;
+    return std::string{};
   }
   this->stubs->call->mutable_parameters().grpc_timeout = this->grpc_timeout;
   auto resp = this->stubs->call->Refresh();
   if (!resp.is_ok()) {
-    throw std::runtime_error("Failed to refresh lease: error code: " +
+    const std::string err = "Failed to refresh lease: error code: " +
                             std::to_string(resp.error_code()) +
-                             ", message: " + resp.error_message());
+                            ", message: " + resp.error_message();
+#ifndef _ETCD_NO_EXCEPTIONS
+    throw std::runtime_error(err);
+#endif
+    return err;
   }
   if (resp.value().ttl() == 0) {
-    throw std::out_of_range(
+    const std::string err =
-        "Failed to refresh lease due to expiration: the new TTL is 0.");
+        "Failed to refresh lease due to expiration: the new TTL is 0.";
+#ifndef _ETCD_NO_EXCEPTIONS
+    throw std::out_of_range(err);
+#endif
+    return err;
   }
+  return std::string{};
 }

src/SyncClient.cpp

@@ -288,7 +288,11 @@ class etcd::SyncClient::TokenAuthenticator {
         // auth
         if (!etcd::detail::authenticate(this->channel_, username_, password_,
                                         token_)) {
-          throw std::invalid_argument("Etcd authentication failed: " + token_);
+          // n.b.: no throw here as the failure of auth will be propagated
+          // to client when it is asked to issue requests.
+          //
+          // throw std::invalid_argument("Etcd authentication failed: " +
+          // token_);
         }
       }
     }

src/v3/AsyncGRPC.cpp

@@ -512,7 +512,10 @@ etcdv3::AsyncLeaseKeepAliveAction::AsyncLeaseKeepAliveAction(
       got_tag == (void*) etcdv3::KEEPALIVE_CREATE) {
     // ok
   } else {
-    throw std::runtime_error("Failed to create a lease keep-alive connection");
+    status = grpc::Status(grpc::StatusCode::CANCELLED,
+                          "Failed to create a lease keep-alive connection");
+    // cannot continue for further refresh
+    isCancelled.store(true);
   }
 }
 
@@ -534,7 +537,7 @@ etcd::Response etcdv3::AsyncLeaseKeepAliveAction::Refresh() {
   std::lock_guard<std::recursive_mutex> scope_lock(this->protect_is_cancelled);
 
   auto start_timepoint = std::chrono::high_resolution_clock::now();
-  if (isCancelled) {
+  if (isCancelled.load()) {
     status = grpc::Status::CANCELLED;
     return etcd::Response(ParseResponse(),
                           etcd::detail::duration_till_now(start_timepoint));
@@ -621,9 +624,7 @@ etcd::Response etcdv3::AsyncLeaseKeepAliveAction::Refresh() {
 
 void etcdv3::AsyncLeaseKeepAliveAction::CancelKeepAlive() {
   std::lock_guard<std::recursive_mutex> scope_lock(this->protect_is_cancelled);
-  if (isCancelled == false) {
+  if (!isCancelled.exchange(true)) {
-    isCancelled = true;
-
     void* got_tag = nullptr;
     bool ok = false;
 
@@ -658,7 +659,7 @@ void etcdv3::AsyncLeaseKeepAliveAction::CancelKeepAlive() {
 }
 
 bool etcdv3::AsyncLeaseKeepAliveAction::Cancelled() const {
-  return isCancelled;
+  return isCancelled.load();
 }
 
 etcdv3::ActionParameters&
@@ -782,7 +783,10 @@ etcdv3::AsyncObserveAction::AsyncObserveAction(
       got_tag == (void*) etcdv3::ELECTION_OBSERVE_CREATE) {
     // n.b.: leave the issue of `Read` to the `waitForResponse`
   } else {
-    throw std::runtime_error("failed to create a observe connection");
+    status = grpc::Status(grpc::StatusCode::CANCELLED,
+                          "failed to create a observe connection");
+    // cannot continue for further observing
+    isCancelled.store(true);
   }
 }
 
@@ -810,7 +814,7 @@ void etcdv3::AsyncObserveAction::waitForResponse() {
 }
 
 void etcdv3::AsyncObserveAction::CancelObserve() {
-  std::lock_guard<std::mutex> scope_lock(this->protect_is_cancalled);
+  std::lock_guard<std::mutex> scope_lock(this->protect_is_cancelled);
   if (!isCancelled.exchange(true)) {
     void* got_tag;
     bool ok = false;
@@ -1130,7 +1134,14 @@ etcdv3::AsyncWatchAction::AsyncWatchAction(etcdv3::ActionParameters&& params)
       got_tag == (void*) etcdv3::WATCH_CREATE) {
     stream->Write(watch_req, (void*) etcdv3::WATCH_WRITE);
   } else {
-    throw std::runtime_error("failed to create a watch connection");
+    status = grpc::Status(grpc::StatusCode::CANCELLED,
+                          "failed to create a watch connection");
+    // cannot continue for further watching
+    isCancelled.store(true);
+  }
+
+  if (!status.ok()) {
+    return;
   }
 
   // wait "write" (WatchCreateRequest) success, and start to read the first
@@ -1138,7 +1149,10 @@ etcdv3::AsyncWatchAction::AsyncWatchAction(etcdv3::ActionParameters&& params)
   if (cq_.Next(&got_tag, &ok) && ok && got_tag == (void*) etcdv3::WATCH_WRITE) {
     stream->Read(&reply, (void*) this);
   } else {
-    throw std::runtime_error("failed to write WatchCreateRequest to server");
+    status = grpc::Status(grpc::StatusCode::CANCELLED,
+                          "failed to write WatchCreateRequest to server");
+    // cannot continue for further watching
+    isCancelled.store(true);
   }
 }
 
@@ -1164,6 +1178,11 @@ void etcdv3::AsyncWatchAction::waitForResponse() {
   bool ok = false;
   bool the_final_round = false;
 
+  // failed to create the watcher
+  if (!status.ok()) {
+    return;
+  }
+
   while (true) {
     if (!the_final_round) {
       if (!cq_.Next(&got_tag, &ok)) {
@@ -1256,6 +1275,14 @@ void etcdv3::AsyncWatchAction::waitForResponse(
   bool ok = false;
   bool the_final_round = false;
 
+  // failed to create the watcher
+  if (!status.ok()) {
+    auto resp = ParseResponse();
+    auto duration = std::chrono::duration_cast<std::chrono::microseconds>(
+        std::chrono::high_resolution_clock::now() - start_timepoint);
+    callback(etcd::Response(resp, duration));
+  }
+
   while (true) {
     if (!the_final_round) {
       if (!cq_.Next(&got_tag, &ok)) {

tst/CMakeLists.txt

@@ -19,6 +19,7 @@ foreach(testfile ${TEST_FILES})
         add_executable(${test_name} EXCLUDE_FROM_ALL ${CMAKE_CURRENT_SOURCE_DIR}/${testfile})
     endif()
     use_cxx(${test_name})
+    set_exceptions(${test_name})
     add_test(NAME ${test_name} COMMAND $<TARGET_FILE:${test_name}>)
 
     target_include_directories(${test_name} PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/../proto/gen)

tst/KeepAliveTest.cpp

@@ -31,7 +31,9 @@ TEST_CASE("keepalive revoke and check if alive") {
   std::this_thread::sleep_for(std::chrono::seconds(1));
 
   // expect keep_alive->Check() to throw exception
+#ifndef _ETCD_NO_EXCEPTIONS
   REQUIRE_THROWS(keepalive->Check());
+#endif
 }
 
 TEST_CASE("keepalive won't expire") {
@@ -45,6 +47,7 @@ TEST_CASE("keepalive won't expire") {
   auto lease_id = resp.value().lease();
   etcd.add(key, meta_str, lease_id);
 
+#ifndef _ETCD_NO_EXCEPTIONS
   std::function<void(std::exception_ptr)> handler =
       [](std::exception_ptr eptr) {
         try {
@@ -57,6 +60,9 @@ TEST_CASE("keepalive won't expire") {
           std::cerr << "Lease expiry \"" << e.what() << "\"\n";
         }
       };
+#else
+  std::function<void(std::exception_ptr)> handler;
+#endif
   etcd::KeepAlive keepalive(etcd, handler, ttl, lease_id);
   std::this_thread::sleep_for(std::chrono::seconds(5));
 }

tst/LockTest.cpp

@@ -117,6 +117,7 @@ TEST_CASE("lock using lease") {
 
   bool failed = false;
 
+#ifndef _ETCD_NO_EXCEPTIONS
   std::function<void(std::exception_ptr)> handler =
       [&failed](std::exception_ptr eptr) {
         try {
@@ -128,6 +129,9 @@ TEST_CASE("lock using lease") {
           failed = true;
         }
       };
+#else
+  std::function<void(std::exception_ptr)> handler;
+#endif
 
   // with handler
   {

tst/MemLeakTest.cpp

@@ -24,7 +24,6 @@ class DistributedLock {
 DistributedLock::DistributedLock(const std::string& lock_name, uint timeout) {
   _etcd_client = std::unique_ptr<etcd::Client>(new etcd::Client(etcd_url));
 
-  try {
   if (timeout == 0) {
     etcd::Response resp = _etcd_client->lock(lock_name).get();
     if (resp.is_ok()) {
@@ -32,14 +31,12 @@ DistributedLock::DistributedLock(const std::string& lock_name, uint timeout) {
       _acquired = true;
     }
   } else {
-      std::future<etcd::Response> future =
+    std::future<etcd::Response> future = std::async(std::launch::async, [&]() {
-          std::async(std::launch::async, [&]() {
       etcd::Response resp = _etcd_client->lock(lock_name).get();
       return resp;
     });
 
-      std::future_status status =
+    std::future_status status = future.wait_for(std::chrono::seconds(timeout));
-          future.wait_for(std::chrono::seconds(timeout));
     if (status == std::future_status::ready) {
       auto resp = future.get();
       if (resp.is_ok()) {
@@ -53,9 +50,6 @@ DistributedLock::DistributedLock(const std::string& lock_name, uint timeout) {
       std::cerr << "failed to acquire distributed lock" << std::endl;
     }
   }
-  } catch (std::exception& e) {
-    std::cerr << "failed to construct: " << e.what() << std::endl;
-  }
 }
 
 DistributedLock::~DistributedLock() noexcept {
@@ -63,14 +57,10 @@ DistributedLock::~DistributedLock() noexcept {
     return;
   }
 
-  try {
   auto resp = _etcd_client->unlock(_lock_key).get();
   if (!resp.is_ok()) {
     std::cout << resp.error_code() << std::endl;
   }
-  } catch (std::exception& e) {
-    std::cerr << "failed to destruct: " << e.what() << std::endl;
-  }
 }
 
 int main() {

tst/RewatchTest.cpp

@@ -37,6 +37,7 @@ void print_response(etcd::Response const& resp) {
 void wait_for_connection(std::string endpoints) {
   // wait until the client connects to etcd server
   while (true) {
+#ifndef _ETCD_NO_EXCEPTIONS
     try {
       etcd::Client client(endpoints);
       if (client.head().get().is_ok()) {
@@ -45,6 +46,12 @@ void wait_for_connection(std::string endpoints) {
     } catch (...) {
       // pass
     }
+#else
+    etcd::Client client(endpoints);
+    if (client.head().get().is_ok()) {
+      break;
+    }
+#endif
     sleep(1);
   }
 }
@@ -85,6 +92,7 @@ TEST_CASE("watch should can be re-established") {
 
   // issue some changes to see if the watcher works
   for (int round = 0; round < 100000; ++round) {
+#ifndef _ETCD_NO_EXCEPTIONS
     try {
       etcd::Client client(etcd_url);
       auto response =
@@ -92,6 +100,11 @@ TEST_CASE("watch should can be re-established") {
     } catch (...) {
       // pass
     }
+#else
+    etcd::Client client(etcd_url);
+    auto response =
+        client.set(my_prefix + "/foo", "bar-" + std::to_string(round)).get();
+#endif
 
     std::this_thread::sleep_for(std::chrono::seconds(2));
   }
@@ -101,6 +114,7 @@ TEST_CASE("watch should can be re-established") {
 
   // the watcher has been cancelled and shouldn't work anymore
   for (int round = 10; round < 20; ++round) {
+#ifndef _ETCD_NO_EXCEPTIONS
     try {
       etcd::Client client(etcd_url);
       auto response =
@@ -108,6 +122,11 @@ TEST_CASE("watch should can be re-established") {
     } catch (...) {
       // pass
     }
+#else
+    etcd::Client client(etcd_url);
+    auto response =
+        client.set(my_prefix + "/foo", "bar-" + std::to_string(round)).get();
+#endif
 
     std::this_thread::sleep_for(std::chrono::seconds(2));
   }