Move trace into its own library in libs.

Apparently it has no testing variant.

1 files changed, 45 insertions, 0 deletions

diff --git a/src/lib/trace/events.h b/src/lib/trace/events.h
new file mode 100644
index 0000000000..761a0f4eb8
--- /dev/null
+++ b/src/lib/trace/events.h
@@ -0,0 +1,45 @@
+/* Copyright (c) 2017-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file events.h
+ * \brief Header file for Tor event tracing.
+ **/
+
+#ifndef TOR_TRACE_EVENTS_H
+#define TOR_TRACE_EVENTS_H
+
+/*
+ * The following defines a generic event tracing function name that has to be
+ * used to trace events in the code base.
+ *
+ * That generic function is then defined by a event tracing framework. For
+ * instance, the "log debug" framework sends all trace events to log_debug()
+ * which is defined in src/trace/debug.h which can only be enabled at compile
+ * time (--enable-event-tracing-debug).
+ *
+ * By default, every trace events in the code base are replaced by a NOP. See
+ * doc/HACKING/Tracing.md for more information on how to use event tracing or
+ * add events.
+ */
+
+#ifdef TOR_EVENT_TRACING_ENABLED
+/* Map every trace event to a per subsystem macro. */
+#define tor_trace(subsystem, name, ...) \
+  tor_trace_##subsystem(name, __VA_ARGS__)
+
+/* Enable event tracing for the debug framework where all trace events are
+ * mapped to a log_debug(). */
+#ifdef USE_EVENT_TRACING_DEBUG
+#include "trace/debug.h"
+#endif
+
+#else /* TOR_EVENT_TRACING_ENABLED */
+
+/* Reaching this point, we NOP every event declaration because event tracing
+ * is not been enabled at compile time. */
+#define tor_trace(subsystem, name, args...)
+
+#endif /* TOR_EVENT_TRACING_ENABLED */
+
+#endif /* TOR_TRACE_EVENTS_H */