gsttraceutils: actually disable tracing system hooks if configured

`./configure --disable-gst-tracer-hooks` didn't do anything, hooks were
always enabled regardless of the option. It works correctly in the
Meson build though.

configure.ac

@@ -89,6 +89,10 @@ AG_GST_CHECK_SUBSYSTEM_DISABLE(GST_DEBUG,[debugging subsystem])
 AM_CONDITIONAL(GST_DISABLE_GST_DEBUG, test "x$GST_DISABLE_GST_DEBUG" = "xyes")
 AG_GST_CHECK_SUBSYSTEM_DISABLE(GST_TRACER_HOOKS,[tracing subsystem hooks])
 AM_CONDITIONAL(GST_DISABLE_GST_TRACER_HOOKS, test "x$GST_DISABLE_GST_TRACER_HOOKS" = "xyes")
+if test "x$GST_DISABLE_GST_TRACER_HOOKS" = xyes; then
+  AC_DEFINE(GST_DISABLE_GST_TRACER_HOOKS, 1,
+    [Define if tracing subsystem hooks is disabled])
+fi
 AG_GST_CHECK_SUBSYSTEM_DISABLE(PARSE,[command-line parser])
 AM_CONDITIONAL(GST_DISABLE_PARSE, test "x$GST_DISABLE_PARSE" = "xyes")
 if test "x$GST_DISABLE_PARSE" = xyes; then

gst/gsttracerutils.c

@@ -196,4 +196,12 @@ gst_tracing_register_hook (GstTracer * tracer, const gchar * detail,
   gst_tracing_register_hook_id (tracer, g_quark_try_string (detail), func);
 }
 
+#else /* !GST_DISABLE_GST_TRACER_HOOKS */
+
+void
+gst_tracing_register_hook (GstTracer * tracer, const gchar * detail,
+    GCallback func)
+{
+}
+
 #endif /* GST_DISABLE_GST_TRACER_HOOKS */

gst/gsttracerutils.h

@@ -697,6 +697,17 @@ typedef void (*GstTracerHookObjectDestroyed) (GObject *self, GstClockTime ts,
 
 #else /* !GST_DISABLE_GST_TRACER_HOOKS */
 
+static inline void
+_priv_gst_tracing_init (void)
+{
+  GST_DEBUG ("Tracing hooks are disabled");
+}
+
+static inline void
+_priv_gst_tracing_deinit (void)
+{
+}
+
 #define GST_TRACER_PAD_PUSH_PRE(pad, buffer)
 #define GST_TRACER_PAD_PUSH_POST(pad, res)
 #define GST_TRACER_PAD_PUSH_LIST_PRE(pad, list)

plugins/Makefile.am

@@ -1,4 +1,7 @@
-SUBDIRS = elements tracers
+SUBDIRS = elements
+
+if !GST_DISABLE_GST_TRACER_HOOKS
+SUBDIRS += tracers
+endif
 
 DIST_SUBDIRS = elements tracers
-