InputPlugin: allow init() to soft-fail

Add enum InputResult which is a tri-state.  Input plugins may now fail
and just become unavailable.

src/input/plugins/CdioParanoiaInputPlugin.cxx

@@ -87,7 +87,7 @@ static constexpr Domain cdio_domain("cdio");
 
 static bool default_reverse_endian;
 
-static bool
+static InputPlugin::InitResult
 input_cdio_init(const config_param &param, Error &error)
 {
 	const char *value = param.GetBlockValue("default_byte_order");
@@ -100,11 +100,11 @@ input_cdio_init(const config_param &param, Error &error)
 			error.Format(config_domain, 0,
 				     "Unrecognized 'default_byte_order' setting: %s",
 				     value);
-			return false;
+			return InputPlugin::InitResult::ERROR;
 		}
 	}
 
-	return true;
+	return InputPlugin::InitResult::SUCCESS;
 }
 
 static void

src/input/plugins/CurlInputPlugin.cxx

@@ -595,7 +595,7 @@ CurlMulti::OnTimeout()
  *
  */
 
-static bool
+static InputPlugin::InitResult
 input_curl_init(const config_param &param, Error &error)
 {
 	CURLcode code = curl_global_init(CURL_GLOBAL_ALL);
@@ -603,7 +603,7 @@ input_curl_init(const config_param &param, Error &error)
 		error.Format(curl_domain, code,
 			     "curl_global_init() failed: %s",
 			     curl_easy_strerror(code));
-		return false;
+		return InputPlugin::InitResult::UNAVAILABLE;
 	}
 
 	const auto version_info = curl_version_info(CURLVERSION_FIRST);
@@ -634,12 +634,14 @@ input_curl_init(const config_param &param, Error &error)
 
 	CURLM *multi = curl_multi_init();
 	if (multi == nullptr) {
+		curl_slist_free_all(http_200_aliases);
+		curl_global_cleanup();
 		error.Set(curl_domain, 0, "curl_multi_init() failed");
-		return false;
+		return InputPlugin::InitResult::UNAVAILABLE;
 	}
 
 	curl_multi = new CurlMulti(io_thread_get(), multi);
-	return true;
+	return InputPlugin::InitResult::SUCCESS;
 }
 
 static void

src/input/plugins/FfmpegInputPlugin.cxx

@@ -69,7 +69,7 @@ input_ffmpeg_supported(void)
 	return avio_enum_protocols(&opaque, 0) != nullptr;
 }
 
-static bool
+static InputPlugin::InitResult
 input_ffmpeg_init(gcc_unused const config_param &param,
 		  Error &error)
 {
@@ -78,10 +78,10 @@ input_ffmpeg_init(gcc_unused const config_param &param,
 	/* disable this plugin if there's no registered protocol */
 	if (!input_ffmpeg_supported()) {
 		error.Set(ffmpeg_domain, "No protocol");
-		return false;
+		return InputPlugin::InitResult::UNAVAILABLE;
 	}
 
-	return true;
+	return InputPlugin::InitResult::SUCCESS;
 }
 
 static InputStream *

src/input/plugins/SmbclientInputPlugin.cxx

@@ -91,17 +91,17 @@ public:
  *
  */
 
-static bool
+static InputPlugin::InitResult
 input_smbclient_init(gcc_unused const config_param &param, Error &error)
 {
 	if (!SmbclientInit(error))
-		return false;
+		return InputPlugin::InitResult::UNAVAILABLE;
 
 	// TODO: create one global SMBCCTX here?
 
 	// TODO: evaluate config_param, call smbc_setOption*()
 
-	return true;
+	return InputPlugin::InitResult::SUCCESS;
 }
 
 static InputStream *