[PATCH 1/2] Fix varobj updation after symbol removal

[Taimoor Mirza <tmirza at codesourcery dot com>]

This problem was observed while loading and unloading symbols using 
add-symbol-file and remove-symbol-file. When remove-symbol-file 
command is invoked, it calls clear_symtab_users that calls varobj_invalidate 
to invalidate variable objects. This function invalidates the varobjs 
that are tied to locals and re-create the ones that are defined on 
globals. During this re-creation of globals, variable objects are 
re-evaluated that can result in new value. But this change is not recorded
and because of this, -var-update for such modified variable objects
gives empty change list.

Proposed Fix:
=============
GDB has mechanism of marking varobj's updated if they are set via 
varobj_set_value operation. This allows any next -var-update to report 
this change. Same approach should be used during varobj invalidation.
If value of newly created varobj is different from previous one, mark it 
updated so that -var-update can get this change.

Variable object invalidation code is cleaned up to avoid using pointers 
whose target has been already freed.

Fix Testing:
===========
This fix has been regression tested on both simulator and real boards.

2014-06-27  Taimoor Mirza  <tmirza@codesourcery.com>
        Maciej W. Rozycki  <macro@codesourcery.com>

        gdb/
        * varobj.h (varobj_is_valid_p, varobj_set_invalid): New
        prototypes.
        * varobj.c (varobj_is_valid_p, varobj_set_invalid): New functions.
        (varobj_invalidate_iter): Mark re-created global object updated
        if its value is different from previous value.
        * objfiles.c (invalidate_objfile_varobj_type_iter): New function.
        (free_objfile): Call it.

---
 gdb/objfiles.c |   19 +++++++++++++++++++
 gdb/varobj.c   |   37 +++++++++++++++++++++++++++++++++++++
 gdb/varobj.h   |    3 +++
 3 files changed, 59 insertions(+)

diff --git a/gdb/objfiles.c b/gdb/objfiles.c
index 0a0b1cb..03559a3 100644
--- a/gdb/objfiles.c
+++ b/gdb/objfiles.c
@@ -32,6 +32,7 @@
 #include "bcache.h"
 #include "expression.h"
 #include "parser-defs.h"
+#include "varobj.h"
 
 #include "gdb_assert.h"
 #include <sys/types.h>
@@ -538,6 +539,21 @@ free_objfile_separate_debug (struct objfile *objfile)
     }
 }
 
+/* Mark the variable object VAR invalid if built upon a type coming from
+   the objfile requested, passed as DATA.  Also clear the type reference.  */
+
+static void
+invalidate_objfile_varobj_type_iter (struct varobj *var, void *data)
+{
+  struct objfile *objfile = data;
+
+  if (varobj_is_valid_p (var) && TYPE_OBJFILE (var->type) == objfile)
+    {
+      varobj_set_invalid (var);
+      var->type = NULL;
+    }
+}
+
 /* Destroy an objfile and all the symtabs and psymtabs under it.  */
 
 void
@@ -584,6 +600,9 @@ free_objfile (struct objfile *objfile)
      lists.  */
   preserve_values (objfile);
 
+  /* Varobj may refer to types stored in objfile's obstack.  */
+  all_root_varobjs (invalidate_objfile_varobj_type_iter, objfile);
+
   /* It still may reference data modules have associated with the objfile and
      the symbol file data.  */
   forget_cached_source_info_for_objfile (objfile);
diff --git a/gdb/varobj.c b/gdb/varobj.c
index 7446f10..2a563af 100644
--- a/gdb/varobj.c
+++ b/gdb/varobj.c
@@ -2683,6 +2683,22 @@ varobj_floating_p (struct varobj *var)
   return var->root->floating;
 }
 
+/* Get the valid flag of varobj VAR.  */
+
+int
+varobj_is_valid_p (struct varobj *var)
+{
+  return var->root->is_valid;
+}
+
+/* Clear the valid flag on varobj VAR.  */
+
+void
+varobj_set_invalid (struct varobj *var)
+{
+  var->root->is_valid = 0;
+}
+
 /* Implement the "value_is_changeable_p" varobj callback for most
    languages.  */
 
@@ -2762,6 +2778,7 @@ varobj_invalidate_iter (struct varobj *var, void *unused)
   if (var->root->floating || var->root->valid_block == NULL)
     {
       struct varobj *tmp_var;
+      char *tmp_var_value, *var_value;
 
       /* Try to create a varobj with same expression.  If we succeed
 	 replace the old varobj, otherwise invalidate it.  */
@@ -2770,6 +2787,26 @@ varobj_invalidate_iter (struct varobj *var, void *unused)
       if (tmp_var != NULL) 
 	{ 
 	  tmp_var->obj_name = xstrdup (var->obj_name);
+	  tmp_var_value = varobj_get_value (tmp_var);
+	  var_value = varobj_get_value (var);
+
+	  /* As varobjs are re-evaluated during creation so there is a
+	     chance that new value is different from old one.  Compare
+	     value of old varobj and newly created varobj and mark
+	     varobj updated If new value is different.  */
+	  if (var_value == NULL && tmp_var_value == NULL)
+	    ; /* Equal.  */
+	  else if (var_value == NULL || tmp_var_value == NULL)
+	    tmp_var->updated = 1;
+	  else
+	    {
+	      /* Mark tmp_var updated if new value is different.  */
+	      if (strcmp (tmp_var_value, var_value) != 0)
+		tmp_var->updated = 1;
+	    }
+
+	  xfree (tmp_var_value);
+	  xfree (var_value);
 	  varobj_delete (var, NULL, 0);
 	  install_variable (tmp_var);
 	}
diff --git a/gdb/varobj.h b/gdb/varobj.h
index 74d41cf..7439a94 100644
--- a/gdb/varobj.h
+++ b/gdb/varobj.h
@@ -299,6 +299,9 @@ extern int varobj_editable_p (struct varobj *var);
 
 extern int varobj_floating_p (struct varobj *var);
 
+extern int varobj_is_valid_p (struct varobj *var);
+extern void varobj_set_invalid (struct varobj *var);
+
 extern void varobj_set_visualizer (struct varobj *var,
 				   const char *visualizer);
 
-- 
1.7.9.5