Merge branch 'future_misuse_exeption' into 'master'

[IO] add FutureError and throw it when wait is called on a Future with callback

See merge request !91

emper/io/Future.cpp

@@ -44,6 +44,10 @@ template PartialCompletableFuture::CompletionType
 PartialCompletableFuture::tryComplete<CallerEnvironment::ANYWHERE>(int32_t res);
 
 auto Future::wait() -> int32_t {
+	if (unlikely(callback)) {
+		throw FutureError("Futures with registered callback must not be awaited");
+	}
+
 	LOGD("Waiting on " << this);
 
 	sem.wait();

emper/io/Future.hpp

@@ -11,6 +11,8 @@
 #include <cstdlib>	// for abort
 #include <functional>
 #include <ostream>	// for operator<<, ostream, basic_ost...
+#include <stdexcept>
+#include <string>
 
 #include "BinaryPrivateSemaphore.hpp"	 // for BPS
 #include "CallerEnvironment.hpp"			 // for CallerEnvironment, ANYWHERE
@@ -25,6 +27,11 @@ struct io_uring_sqe;
 namespace emper::io {
 class Stats;
 
+class FutureError : public std::logic_error {
+	friend class Future;
+	FutureError(const std::string& what) : std::logic_error(what) {}
+};
+
 /*
  * @brief Future representing an IO request which can be awaited
  */
@@ -115,6 +122,11 @@ class Future : public Logger<LogSubsystem::IO> {
 			: op(op), fd(fd), buf(buf), len(len), offsetOrFlags(offsetOrFlags){};
 
  public:
+	// Clang-tidy warns about the exception possibly thrown by
+	// ~Future -> cancel -> wait
+	// But this exception will never be thrown because wait() throws an exception
+	// only if callback is set and if callback is set ~Future does not call cancel.
+	// NOLINTNEXTLINE(bugprone-exception-escape)
 	virtual ~Future() {
 		if (isForgotten() || callback) {
 			return;