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

Taimoor Mirza
2015-04-16T03:33:29Z

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.

2015-04-15 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.

Signed-off-by: Taimoor Mirza <tmirza@codesourcery.com>
---
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 ff20bc8..5905998 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 <sys/types.h>
#include <sys/stat.h>
@@ -533,6 +534,21 @@ 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
@@ -579,6 +595,9 @@ 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 b220fd8..4860a37 100644
--- a/gdb/varobj.c
+++ b/gdb/varobj.c
@@ -2699,6 +2699,22 @@ varobj_floating_p (const 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. */

@@ -2760,6 +2776,7 @@ 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. */
@@ -2768,6 +2785,26 @@ 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 8860526..4afb9e8 100644
--- a/gdb/varobj.h
+++ b/gdb/varobj.h
@@ -311,6 +311,9 @@ extern int varobj_editable_p (const struct varobj *var);

extern int varobj_floating_p (const 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