info: Add a 'flags' parametter to gst_debug_get_stack_trace

This is an API break but that API has not been released yet.

We are passing a flag rather than a simple boolean as we can imagine
to implement more features in the future for example to retrieve a
stack trace for all the threads, etc..

Retrieving source file and line numbers is pretty
expensive while getting a stack trace, this new argument
allows the user to decide to retrieve a backtrace
without those infos instead which is much faster.

For example running $ GST_LEAKS_TRACER_STACK_TRACE=1 GST_DEBUG=GST_TRACER:7 \
GST_TRACERS=leaks time gst-launch-1.0 videotestsrc num-buffers=1 ! fakesink:

* With simple stack traces:

    0.04s user 0.02s system 99% cpu 0.060 total

* With full stack traces:

    0.66s user 0.23s system 96% cpu 0.926 total

https://bugzilla.gnome.org/show_bug.cgi?id=775423

docs/gst/gstreamer-sections.txt

@@ -1328,6 +1328,7 @@ GST_STR_NULL
 GST_DEBUG_PAD_NAME
 GST_FUNCTION
 GstLogFunction
+GstStackTraceFlags
 gst_debug_log
 gst_debug_log_valist
 gst_debug_message_get

gst/gstinfo.c

@@ -2646,7 +2646,7 @@ append_debug_info (GString * trace, Dwfl * dwfl, const void *ip)
 #endif /* HAVE_DW */
 
 static gchar *
-generate_unwind_trace (void)
+generate_unwind_trace (GstStackTraceFlags flags)
 {
   unw_context_t uc;
   unw_cursor_t cursor;
@@ -2654,14 +2654,14 @@ generate_unwind_trace (void)
   GString *trace = g_string_new (NULL);
 
 #ifdef HAVE_DW
-  Dwfl *dwfl;
-
+  Dwfl *dwfl = NULL;
   Dwfl_Callbacks callbacks = {
     .find_elf = dwfl_linux_proc_find_elf,
     .find_debuginfo = dwfl_standard_find_debuginfo,
   };
 
-  dwfl = dwfl_begin (&callbacks);
+  if ((flags & GST_STACK_TRACE_SHOW_FULL))
+    dwfl = dwfl_begin (&callbacks);
 #endif /* HAVE_DW */
 
   unw_getcontext (&uc);
@@ -2691,7 +2691,8 @@ generate_unwind_trace (void)
   }
 
 #ifdef HAVE_DW
-  dwfl_end (dwfl);
+  if (dwfl)
+    dwfl_end (dwfl);
 #endif
 
   return g_string_free (trace, FALSE);
@@ -2725,26 +2726,35 @@ generate_backtrace_trace (void)
 
 /**
  * gst_debug_get_stack_trace:
+ * @flags: A set of #GstStackTraceFlags to determine how the stack
+ * trace should look like. Pass 0 to retrieve a minimal backtrace.
  *
  * If libunwind or glibc backtrace are present, a stack trace
  * is returned.
+ *
+ * Since: 1.12
  */
 gchar *
-gst_debug_get_stack_trace (void)
+gst_debug_get_stack_trace (GstStackTraceFlags flags)
 {
   gchar *trace = NULL;
+#ifdef HAVE_BACKTRACE
+  gboolean have_backtrace = TRUE;
+#else
+  gboolean have_backtrace = FALSE;
+#endif
 
 #ifdef HAVE_UNWIND
-  trace = generate_unwind_trace ();
-  if (trace)
-    return trace;
+  if ((flags & GST_STACK_TRACE_SHOW_FULL) || !have_backtrace)
+    trace = generate_unwind_trace (flags);
 #endif /* HAVE_UNWIND */
 
-#ifdef HAVE_BACKTRACE
-  trace = generate_backtrace_trace ();
-#endif /* HAVE_BACKTRACE */
+  if (trace)
+    return trace;
+  else if (have_backtrace)
+    return generate_backtrace_trace ();
 
-  return trace;
+  return NULL;
 }
 
 /**
@@ -2756,7 +2766,7 @@ gst_debug_get_stack_trace (void)
 void
 gst_debug_print_stack_trace (void)
 {
-  gchar *trace = gst_debug_get_stack_trace ();
+  gchar *trace = gst_debug_get_stack_trace (GST_STACK_TRACE_SHOW_FULL);
 
   if (trace)
     g_print ("%s\n", trace);

gst/gstinfo.h

@@ -175,6 +175,15 @@ typedef enum {
   GST_DEBUG_UNDERLINE		= 0x0200
 } GstDebugColorFlags;
 
+/**
+ * GstStackTraceFlags:
+ * @GST_STACK_TRACE_SHOW_FULL: Try to retrieve as much information as
+ *                             possible when getting the stack trace
+ */
+typedef enum {
+    GST_STACK_TRACE_SHOW_FULL = 1 << 0
+} GstStackTraceFlags;
+
 /**
  * GstDebugColorMode:
  * @GST_DEBUG_COLOR_MODE_OFF: Do not use colors in logs.
@@ -1570,7 +1579,7 @@ GST_TRACE (const char *format, ...)
 
 
 void gst_debug_print_stack_trace (void);
-gchar * gst_debug_get_stack_trace (void);
+gchar * gst_debug_get_stack_trace (GstStackTraceFlags flags);
 
 G_END_DECLS
 

plugins/tracers/gstleaks.c

@@ -221,7 +221,7 @@ handle_object_created (GstLeaksTracer * self, gpointer object, GType type,
 
   GST_OBJECT_LOCK (self);
   if (self->log_stack_trace) {
-    trace = gst_debug_get_stack_trace ();
+    trace = gst_debug_get_stack_trace (GST_STACK_TRACE_SHOW_FULL);
   }
 
   g_hash_table_insert (self->objects, object, trace);
@@ -264,7 +264,7 @@ gst_leaks_tracer_init (GstLeaksTracer * self)
     gchar *trace;
 
     /* Test if we can retrieve backtrace */
-    trace = gst_debug_get_stack_trace ();
+    trace = gst_debug_get_stack_trace (GST_STACK_TRACE_SHOW_FULL);
     if (trace) {
       self->log_stack_trace = TRUE;
       g_free (trace);