From 308010794a032669313bf989dd8421b9f1a8cba3 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Thu, 8 Sep 2016 17:14:11 +0200
Subject: [PATCH] decoder/Control: convert error from Error to
 std::exception_ptr

Prepare full C++ exception support in the decoder thread.
---
 src/decoder/DecoderControl.cxx |  1 +
 src/decoder/DecoderControl.hxx | 28 +++++++++++++---------------
 src/decoder/DecoderThread.cxx  | 22 ++++++++++++++++------
 src/player/Thread.cxx          |  8 +++++---
 4 files changed, 35 insertions(+), 24 deletions(-)

diff --git a/src/decoder/DecoderControl.cxx b/src/decoder/DecoderControl.cxx
index e32a3cad8..c4250be0e 100644
--- a/src/decoder/DecoderControl.cxx
+++ b/src/decoder/DecoderControl.cxx
@@ -22,6 +22,7 @@
 #include "DecoderError.hxx"
 #include "MusicPipe.hxx"
 #include "DetachedSong.hxx"
+#include "util/Error.hxx"
 
 #include <assert.h>
 
diff --git a/src/decoder/DecoderControl.hxx b/src/decoder/DecoderControl.hxx
index d1d385d43..e3ef63192 100644
--- a/src/decoder/DecoderControl.hxx
+++ b/src/decoder/DecoderControl.hxx
@@ -27,7 +27,8 @@
 #include "thread/Cond.hxx"
 #include "thread/Thread.hxx"
 #include "Chrono.hxx"
-#include "util/Error.hxx"
+
+#include <exception>
 
 #include <utility>
 
@@ -39,6 +40,7 @@
 #undef ERROR
 #endif
 
+class Error;
 class DetachedSong;
 class MusicBuffer;
 class MusicPipe;
@@ -97,7 +99,7 @@ struct DecoderControl {
 	 * The object must be freed when this object transitions to
 	 * any other state (usually #DecoderState::START).
 	 */
-	Error error;
+	std::exception_ptr error;
 
 	bool quit;
 
@@ -242,29 +244,25 @@ struct DecoderControl {
 	}
 
 	/**
-	 * Checks whether an error has occurred, and if so, returns a
-	 * copy of the #Error object.
+	 * Checks whether an error has occurred, and if so, rethrows
+	 * it.
 	 *
 	 * Caller must lock the object.
 	 */
-	gcc_pure
-	Error GetError() const {
+	void CheckRethrowError() const {
 		assert(command == DecoderCommand::NONE);
-		assert(state != DecoderState::ERROR || error.IsDefined());
+		assert(state != DecoderState::ERROR || error);
 
-		Error result;
 		if (state == DecoderState::ERROR)
-			result.Set(error);
-		return result;
+			std::rethrow_exception(error);
 	}
 
 	/**
-	 * Like GetError(), but locks and unlocks the object.
+	 * Like CheckRethrowError(), but locks and unlocks the object.
 	 */
-	gcc_pure
-	Error LockGetError() const {
+	void LockCheckRethrowError() const {
 		const ScopeLock protect(mutex);
-		return GetError();
+		CheckRethrowError();
 	}
 
 	/**
@@ -274,7 +272,7 @@ struct DecoderControl {
 	 */
 	void ClearError() {
 		if (state == DecoderState::ERROR) {
-			error.Clear();
+			error = std::exception_ptr();
 			state = DecoderState::STOP;
 		}
 	}
diff --git a/src/decoder/DecoderThread.cxx b/src/decoder/DecoderThread.cxx
index 49b5fd1c4..694c95e66 100644
--- a/src/decoder/DecoderThread.cxx
+++ b/src/decoder/DecoderThread.cxx
@@ -34,6 +34,7 @@
 #include "util/MimeType.hxx"
 #include "util/UriUtil.hxx"
 #include "util/Error.hxx"
+#include "util/RuntimeError.hxx"
 #include "util/Domain.hxx"
 #include "thread/Name.hxx"
 #include "tag/ApeReplayGain.hxx"
@@ -415,7 +416,7 @@ decoder_run_song(DecoderControl &dc,
 		/* copy the Error from struct Decoder to
 		   DecoderControl */
 		dc.state = DecoderState::ERROR;
-		dc.error = std::move(decoder.error);
+		dc.error = std::make_exception_ptr(std::move(decoder.error));
 	} else if (success)
 		dc.state = DecoderState::STOP;
 	else {
@@ -426,8 +427,7 @@ decoder_run_song(DecoderControl &dc,
 		if (!allocated.empty())
 			error_uri = allocated.c_str();
 
-		dc.error.Format(decoder_domain,
-				 "Failed to decode %s", error_uri);
+		dc.error = std::make_exception_ptr(FormatRuntimeError("Failed to decode %s", error_uri));
 	}
 
 	dc.client_cond.signal();
@@ -450,9 +450,11 @@ decoder_run(DecoderControl &dc)
 	Path path_fs = Path::Null();
 	AllocatedPath path_buffer = AllocatedPath::Null();
 	if (PathTraitsUTF8::IsAbsolute(uri_utf8)) {
-		path_buffer = AllocatedPath::FromUTF8(uri_utf8, dc.error);
+		Error error;
+		path_buffer = AllocatedPath::FromUTF8(uri_utf8, error);
 		if (path_buffer.IsNull()) {
 			dc.state = DecoderState::ERROR;
+			dc.error = std::make_exception_ptr(std::move(error));
 			dc.CommandFinishedLocked();
 			return;
 		}
@@ -485,8 +487,16 @@ decoder_task(void *arg)
 
 			decoder_run(dc);
 
-			if (dc.state == DecoderState::ERROR)
-				LogError(dc.error);
+			if (dc.state == DecoderState::ERROR) {
+				try {
+					std::rethrow_exception(dc.error);
+				} catch (const std::exception &e) {
+					LogError(e);
+				} catch (const Error &error) {
+					LogError(error);
+				} catch (...) {
+				}
+			}
 
 			break;
 
diff --git a/src/player/Thread.cxx b/src/player/Thread.cxx
index 4458ba671..1e4a3cc7d 100644
--- a/src/player/Thread.cxx
+++ b/src/player/Thread.cxx
@@ -33,6 +33,7 @@
 #include "tag/Tag.hxx"
 #include "Idle.hxx"
 #include "util/Domain.hxx"
+#include "util/Error.hxx"
 #include "thread/Name.hxx"
 #include "Log.hxx"
 
@@ -372,9 +373,10 @@ Player::StopDecoder()
 bool
 Player::ForwardDecoderError()
 {
-	Error error = dc.GetError();
-	if (error.IsDefined()) {
-		pc.SetError(PlayerError::DECODER, std::move(error));
+	try {
+		dc.CheckRethrowError();
+	} catch (...) {
+		pc.SetError(PlayerError::DECODER, std::current_exception());
 		return false;
 	}