2011-03-17 Phil Muldoon <pmuldoon@redhat.com>

	    * python/py-symtab.c: Populate symtab_object_methods,
	    sal_object_methods.
	    (stpy_is_valid): New function.
	    (salpy_is_valid): Ditto.
	    * python/py-symbol.c: Declare symbol_object_methods.
	    Populate.
	    (sympy_is_valid): New function.
	    * python/py-objfile.c: Declare objfile_object_methods.
	    Populate.
	    (objfpy_is_valid): New function.
	    * python/py-inferior.c: Populate inferior_object_methods.
	    (infpy_is_valid): New function.
	    * python/py-infthread.c: Populate thread_object_methods.
	    (thpy_is_valid): New function.
	    * python/py-block.c: Declare block_object_methods.
	    Populate.  Declare
	    block_iterator_object_methods.  Populate.
	    (blpy_is_valid): New function.
	    (blpy_iter_is_valid): Ditto.

2010-03-17  Phil Muldoon  <pmuldoon@redhat.com>

	    * gdb.python/Makefile.in: Add py-objfile.
	    * gdb.python/py-objfile.exp: New file.
	    * gdb.python/py-objfile.c: New file.
	    * gdb.python/py-block.exp: Add is_valid tests.
	    * gdb.python/py-inferior.exp: Ditto.
	    * gdb.python/py-infthread.exp: Ditto.
	    * gdb.python/py-symbol.exp: Ditto.
	    * gdb.python/py-symtab.exp: Ditto.

2011-03-17  Phil Muldoon  <pmuldoon@redhat.com>

	    * gdb.texinfo (Blocks In Python): Add is_valid method
              description.
	      (Inferiors In Python): Likewise.
	      (Threads In Python): Likewise.
	      (Symbols In Python): Likewise.
	      (Objfiles In Python): Likewise.
	      (Symbol Tables In Python): Likewise.

19 files changed, 427 insertions, 8 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5827164..9645394 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,22 @@
+2011-03-17  Phil Muldoon  <pmuldoon@redhat.com>
+
+	* python/py-symtab.c: Populate symtab_object_methods,
+	sal_object_methods.
+	(stpy_is_valid): New function.
+	(salpy_is_valid): Ditto.
+	* python/py-symbol.c: Declare symbol_object_methods.  Populate.
+	(sympy_is_valid): New function.
+	* python/py-objfile.c: Declare objfile_object_methods.  Populate.
+	(objfpy_is_valid): New function.
+	* python/py-inferior.c: Populate inferior_object_methods.
+	(infpy_is_valid): New function.
+	* python/py-infthread.c: Populate thread_object_methods.
+	(thpy_is_valid): New function.
+	* python/py-block.c: Declare block_object_methods.  Populate.  Declare
+	block_iterator_object_methods.  Populate.
+	(blpy_is_valid): New function.
+	(blpy_iter_is_valid): Ditto.
+
 2011-03-16  Keith Seitz  <keiths@redhat.com>
 
 	* linespec.c (find_methods): Canonicalize NAME before looking
diff --git a/gdb/NEWS b/gdb/NEWS
index e231d5b..feebf61 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -43,6 +43,10 @@
      This improves how Parameter set/show documentation is processed
      and allows for more dynamic content.
 
+  ** Symbols, Symbol Table, Symbol Table and Line, Object Files,
+     Inferior, Inferior Thread, Blocks, and Block Iterator APIs now
+     have an is_valid method.
+
   ** Breakpoints can now be sub-classed in Python, and in particular
      you may implement a 'stop' function that is executed each time
      the inferior reaches that breakpoint.   
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index b7f63eb..658325e 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,12 @@
+2011-03-17  Phil Muldoon  <pmuldoon@redhat.com>
+
+	* gdb.texinfo (Blocks In Python): Add is_valid method description.
+	(Inferiors In Python): Likewise.
+	(Threads In Python): Likewise.
+	(Symbols In Python): Likewise.
+	(Objfiles In Python): Likewise.
+	(Symbol Tables In Python): Likewise.
+
 2011-03-15  Pedro Alves  <pedro@codesourcery.com>
 
 	* gdb.texinfo (Auto Display) <undisplay, enable display, disable
@@ -8,7 +17,6 @@
 	* gdb.texinfo (Breakpoints In Python): Add description and example
 	of Python stop function operation.
 
-
 2011-03-10  Phil Muldoon  <pmuldoon@redhat.com>
 
 	* gdb.texinfo (Parameters In Python): Document get_set_string and
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 0eeb38c..ea1e2f5 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -21870,6 +21870,14 @@ started by @value{GDBN} itself.
 A @code{gdb.Inferior} object has the following methods:
 
 @table @code
+@defmethod Inferior is_valid
+Returns @code{True} if the @code{gdb.Inferior} object is valid,
+@code{False} if not.  A @code{gdb.Inferior} object will become invalid
+if the inferior no longer exists within @value{GDBN}.  All other
+@code{gdb.Inferior} methods will throw an exception if it is invalid
+at the time the method is called.
+@end defmethod
+
 @defmethod Inferior threads
 This method returns a tuple holding all the threads which are valid
 when it is called.  If there are no valid threads, the method will
@@ -22069,6 +22077,14 @@ does not  use that identifier.
 A @code{gdb.InferiorThread} object has the following methods:
 
 @table @code
+@defmethod InferiorThread is_valid
+Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
+@code{False} if not.  A @code{gdb.InferiorThread} object will become
+invalid if the thread exits, or the inferior that the thread belongs
+is deleted.  All other @code{gdb.InferiorThread} methods will throw an
+exception if it is invalid at the time the method is called.
+@end defmethod
+
 @defmethod InferiorThread switch
 This changes @value{GDBN}'s currently selected thread to the one represented
 by this object.
@@ -22662,6 +22678,16 @@ which is used to format the value.  @xref{Pretty Printing API}, for more
 information.
 @end defivar
 
+A @code{gdb.Objfile} object has the following methods:
+
+@defmethod Objfile is_valid
+Returns @code{True} if the @code{gdb.Objfile} object is valid,
+@code{False} if not.  A @code{gdb.Objfile} object can become invalid
+if the object file it refers to is not loaded in @value{GDBN} any
+longer.  All other @code{gdb.Objfile} methods will throw an exception
+if it is invalid at the time the method is called.
+@end defmethod
+
 @node Frames In Python
 @subsubsection Accessing inferior stack frames from Python.
 
@@ -22813,6 +22839,20 @@ block cannot be found for the @var{pc} value specified, the function
 will return @code{None}.
 @end defun
 
+A @code{gdb.Block} object has the following methods:
+
+@table @code
+@defmethod Block is_valid
+Returns @code{True} if the @code{gdb.Block} object is valid,
+@code{False} if not.  A block object can become invalid if the block it
+refers to doesn't exist anymore in the inferior.  All other
+@code{gdb.Block} methods will throw an exception if it is invalid at
+the time the method is called.  This method is also made available to
+the Python iterator object that @code{gdb.Block} provides in an iteration
+context and via the Python @code{iter} built-in function.
+@end defmethod
+@end table
+
 A @code{gdb.Block} object has the following attributes:
 
 @table @code
@@ -22935,6 +22975,18 @@ of a symbol.  Each address class is a constant defined in the
 @end defivar
 @end table
 
+A @code{gdb.Symbol} object has the following methods:
+
+@table @code
+@defmethod Symbol is_valid
+Returns @code{True} if the @code{gdb.Symbol} object is valid,
+@code{False} if not.  A @code{gdb.Symbol} object can become invalid if
+the symbol it refers to does not exist in @value{GDBN} any longer.
+All other @code{gdb.Symbol} methods will throw an exception if it is
+invalid at the time the method is called.
+@end defmethod
+@end table
+
 The available domain categories in @code{gdb.Symbol} are represented
 as constants in the @code{gdb} module:
 
@@ -23079,6 +23131,19 @@ attribute is not writable.
 @end defivar
 @end table
 
+A @code{gdb.Symtab_and_line} object has the following methods:
+
+@table @code
+@defmethod Symtab_and_line is_valid
+Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
+@code{False} if not.  A @code{gdb.Symtab_and_line} object can become
+invalid if the Symbol table and line object it refers to does not
+exist in @value{GDBN} any longer.  All other
+@code{gdb.Symtab_and_line} methods will throw an exception if it is
+invalid at the time the method is called.
+@end defmethod
+@end table
+
 A @code{gdb.Symtab} object has the following attributes:
 
 @table @code
@@ -23092,9 +23157,17 @@ This attribute is not writable.
 @end defivar
 @end table
 
-The following methods are provided:
+A @code{gdb.Symtab} object has the following methods:
 
 @table @code
+@defmethod Symtab is_valid
+Returns @code{True} if the @code{gdb.Symtab} object is valid,
+@code{False} if not.  A @code{gdb.Symtab} object can become invalid if
+the symbol table it refers to does not exist in @value{GDBN} any
+longer.  All other @code{gdb.Symtab} methods will throw an exception
+if it is invalid at the time the method is called.
+@end defmethod
+
 @defmethod Symtab fullname
 Return the symbol table's source absolute file name.
 @end defmethod
diff --git a/gdb/python/py-block.c b/gdb/python/py-block.c
index 9d0d6cc..08d4455 100644
--- a/gdb/python/py-block.c
+++ b/gdb/python/py-block.c
@@ -263,6 +263,36 @@ blpy_block_syms_dealloc (PyObject *obj)
   Py_XDECREF (iter_obj->source);
 }
 
+/* Implementation of gdb.Block.is_valid (self) -> Boolean.
+   Returns True if this block object still exists in GDB.  */
+
+static PyObject *
+blpy_is_valid (PyObject *self, PyObject *args)
+{
+  struct block *block;
+
+  block = block_object_to_block (self);
+  if (block == NULL)
+    Py_RETURN_FALSE;
+
+  Py_RETURN_TRUE;
+}
+
+/* Implementation of gdb.BlockIterator.is_valid (self) -> Boolean.
+   Returns True if this block iterator object still exists in GDB  */
+
+static PyObject *
+blpy_iter_is_valid (PyObject *self, PyObject *args)
+{
+  block_syms_iterator_object *iter_obj =
+    (block_syms_iterator_object *) self;
+
+  if (iter_obj->source->block == NULL)
+    Py_RETURN_FALSE;
+
+  Py_RETURN_TRUE;
+}
+
 /* Return the innermost lexical block containing the specified pc value,
    or 0 if there is none.  */
 PyObject *
@@ -342,6 +372,13 @@ gdbpy_initialize_blocks (void)
 
 
 
+static PyMethodDef block_object_methods[] = {
+  { "is_valid", blpy_is_valid, METH_NOARGS,
+    "is_valid () -> Boolean.\n\
+Return true if this block is valid, false if not." },
+  {NULL}  /* Sentinel */
+};
+
 static PyGetSetDef block_object_getset[] = {
   { "start", blpy_get_start, NULL, "Start address of the block.", NULL },
   { "end", blpy_get_end, NULL, "End address of the block.", NULL },
@@ -381,11 +418,18 @@ PyTypeObject block_object_type = {
   0,				  /* tp_weaklistoffset */
   blpy_iter,			  /* tp_iter */
   0,				  /* tp_iternext */
-  0,				  /* tp_methods */
+  block_object_methods,		  /* tp_methods */
   0,				  /* tp_members */
   block_object_getset		  /* tp_getset */
 };
 
+static PyMethodDef block_iterator_object_methods[] = {
+  { "is_valid", blpy_iter_is_valid, METH_NOARGS,
+    "is_valid () -> Boolean.\n\
+Return true if this block iterator is valid, false if not." },
+  {NULL}  /* Sentinel */
+};
+
 static PyTypeObject block_syms_iterator_object_type = {
   PyObject_HEAD_INIT (NULL)
   0,				  /*ob_size*/
@@ -415,5 +459,5 @@ static PyTypeObject block_syms_iterator_object_type = {
   0,				  /*tp_weaklistoffset */
   blpy_block_syms_iter,           /*tp_iter */
   blpy_block_syms_iternext,	  /*tp_iternext */
-  0				  /*tp_methods */
+  block_iterator_object_methods   /*tp_methods */
 };
diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index ee41ea7..b9df394 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -606,6 +606,20 @@ infpy_search_memory (PyObject *self, PyObject *args, PyObject *kw)
     Py_RETURN_NONE;
 }
 
+/* Implementation of gdb.Inferior.is_valid (self) -> Boolean.
+   Returns True if this inferior object still exists in GDB.  */
+
+static PyObject *
+infpy_is_valid (PyObject *self, PyObject *args)
+{
+  inferior_object *inf = (inferior_object *) self;
+
+  if (! inf->inferior)
+    Py_RETURN_FALSE;
+
+  Py_RETURN_TRUE;
+}
+
 
 /* Clear the INFERIOR pointer in an Inferior object and clear the
    thread list.  */
@@ -676,6 +690,9 @@ static PyGetSetDef inferior_object_getset[] =
 
 static PyMethodDef inferior_object_methods[] =
 {
+  { "is_valid", infpy_is_valid, METH_NOARGS,
+    "is_valid () -> Boolean.\n\
+Return true if this inferior is valid, false if not." },
   { "threads", infpy_threads, METH_NOARGS,
     "Return all the threads of this inferior." },
   { "read_memory", (PyCFunction) infpy_read_memory,
diff --git a/gdb/python/py-infthread.c b/gdb/python/py-infthread.c
index 059422d..b37c53c 100644
--- a/gdb/python/py-infthread.c
+++ b/gdb/python/py-infthread.c
@@ -222,7 +222,20 @@ thpy_is_exited (PyObject *self, PyObject *args)
   Py_RETURN_FALSE;
 }
 
+/* Implementation of gdb.InfThread.is_valid (self) -> Boolean.
+   Returns True if this inferior Thread object still exists
+   in GDB.  */
 
+static PyObject *
+thpy_is_valid (PyObject *self, PyObject *args)
+{
+  thread_object *thread_obj = (thread_object *) self;
+
+  if (! thread_obj->thread)
+    Py_RETURN_FALSE;
+
+  Py_RETURN_TRUE;
+}
 
 /* Implementation of gdb.selected_thread () -> gdb.InferiorThread.
    Returns the selected thread object.  */
@@ -269,6 +282,9 @@ static PyGetSetDef thread_object_getset[] =
 
 static PyMethodDef thread_object_methods[] =
 {
+  { "is_valid", thpy_is_valid, METH_NOARGS,
+    "is_valid () -> Boolean.\n\
+Return true if this inferior thread is valid, false if not." },
   { "switch", thpy_switch, METH_NOARGS,
     "switch ()\n\
 Makes this the GDB selected thread." },
diff --git a/gdb/python/py-objfile.c b/gdb/python/py-objfile.c
index 7f9d9ee..f9821f5 100644
--- a/gdb/python/py-objfile.c
+++ b/gdb/python/py-objfile.c
@@ -118,6 +118,20 @@ objfpy_set_printers (PyObject *o, PyObject *value, void *ignore)
   return 0;
 }
 
+/* Implementation of gdb.Objfile.is_valid (self) -> Boolean.
+   Returns True if this object file still exists in GDB.  */
+
+static PyObject *
+objfpy_is_valid (PyObject *self, PyObject *args)
+{
+  objfile_object *obj = (objfile_object *) self;
+
+  if (! obj->objfile)
+    Py_RETURN_FALSE;
+
+  Py_RETURN_TRUE;
+}
+
 
 
 /* Clear the OBJFILE pointer in an Objfile object and remove the
@@ -181,6 +195,15 @@ gdbpy_initialize_objfile (void)
 
 
 
+static PyMethodDef objfile_object_methods[] =
+{
+  { "is_valid", objfpy_is_valid, METH_NOARGS,
+    "is_valid () -> Boolean.\n\
+Return true if this object file is valid, false if not." },
+
+  { NULL }
+};
+
 static PyGetSetDef objfile_getset[] =
 {
   { "filename", objfpy_get_filename, NULL,
@@ -220,7 +243,7 @@ static PyTypeObject objfile_object_type =
   0,				  /* tp_weaklistoffset */
   0,				  /* tp_iter */
   0,				  /* tp_iternext */
-  0,				  /* tp_methods */
+  objfile_object_methods,	  /* tp_methods */
   0,				  /* tp_members */
   objfile_getset,		  /* tp_getset */
   0,				  /* tp_base */
diff --git a/gdb/python/py-symbol.c b/gdb/python/py-symbol.c
index 2df2336..2c7900f 100644
--- a/gdb/python/py-symbol.c
+++ b/gdb/python/py-symbol.c
@@ -167,6 +167,21 @@ sympy_is_variable (PyObject *self, void *closure)
 			      || class == LOC_OPTIMIZED_OUT));
 }
 
+/* Implementation of gdb.Symbol.is_valid (self) -> Boolean.
+   Returns True if this Symbol still exists in GDB.  */
+
+static PyObject *
+sympy_is_valid (PyObject *self, PyObject *args)
+{
+  struct symbol *symbol = NULL;
+
+  symbol = symbol_object_to_symbol (self);
+  if (symbol == NULL)
+    Py_RETURN_FALSE;
+
+  Py_RETURN_TRUE;
+}
+
 /* Given a symbol, and a symbol_object that has previously been
    allocated and initialized, populate the symbol_object with the
    struct symbol data.  Also, register the symbol_object life-cycle
@@ -420,6 +435,13 @@ to display demangled or mangled names.", NULL },
   { NULL }  /* Sentinel */
 };
 
+static PyMethodDef symbol_object_methods[] = {
+  { "is_valid", sympy_is_valid, METH_NOARGS,
+    "is_valid () -> Boolean.\n\
+Return true if this symbol is valid, false if not." },
+  {NULL}  /* Sentinel */
+};
+
 PyTypeObject symbol_object_type = {
   PyObject_HEAD_INIT (NULL)
   0,				  /*ob_size*/
@@ -449,7 +471,7 @@ PyTypeObject symbol_object_type = {
   0,				  /*tp_weaklistoffset */
   0,				  /*tp_iter */
   0,				  /*tp_iternext */
-  0,				  /*tp_methods */
+  symbol_object_methods,	  /*tp_methods */
   0,				  /*tp_members */
   symbol_object_getset		  /*tp_getset */
 };
diff --git a/gdb/python/py-symtab.c b/gdb/python/py-symtab.c
index 5c1c6bb..107cdec 100644
--- a/gdb/python/py-symtab.c
+++ b/gdb/python/py-symtab.c
@@ -138,6 +138,21 @@ stpy_fullname (PyObject *self, PyObject *args)
   Py_RETURN_NONE;
 }
 
+/* Implementation of gdb.Symtab.is_valid (self) -> Boolean.
+   Returns True if this Symbol table still exists in GDB.  */
+
+static PyObject *
+stpy_is_valid (PyObject *self, PyObject *args)
+{
+  struct symtab *symtab = NULL;
+
+  symtab = symtab_object_to_symtab (self);
+  if (symtab == NULL)
+    Py_RETURN_FALSE;
+
+  Py_RETURN_TRUE;
+}
+
 static PyObject *
 salpy_str (PyObject *self)
 {
@@ -212,6 +227,21 @@ salpy_get_symtab (PyObject *self, void *closure)
   return (PyObject *) self_sal->symtab;
 }
 
+/* Implementation of gdb.Symtab_and_line.is_valid (self) -> Boolean.
+   Returns True if this Symbol table and line object still exists GDB.  */
+
+static PyObject *
+salpy_is_valid (PyObject *self, PyObject *args)
+{
+  struct symtab_and_line *sal;
+
+  sal = sal_object_to_symtab_and_line (self);
+  if (sal == NULL)
+    Py_RETURN_FALSE;
+
+  Py_RETURN_TRUE;
+}
+
 static void
 salpy_dealloc (PyObject *self)
 {
@@ -441,6 +471,9 @@ static PyGetSetDef symtab_object_getset[] = {
 };
 
 static PyMethodDef symtab_object_methods[] = {
+  { "is_valid", stpy_is_valid, METH_NOARGS,
+    "is_valid () -> Boolean.\n\
+Return true if this symbol table is valid, false if not." },
   { "fullname", stpy_fullname, METH_NOARGS,
     "fullname () -> String.\n\
 Return the symtab's full source filename." },
@@ -489,6 +522,13 @@ static PyGetSetDef sal_object_getset[] = {
   {NULL}  /* Sentinel */
 };
 
+static PyMethodDef sal_object_methods[] = {
+  { "is_valid", salpy_is_valid, METH_NOARGS,
+    "is_valid () -> Boolean.\n\
+Return true if this symbol table and line is valid, false if not." },
+  {NULL}  /* Sentinel */
+};
+
 static PyTypeObject sal_object_type = {
   PyObject_HEAD_INIT (NULL)
   0,				  /*ob_size*/
@@ -518,7 +558,7 @@ static PyTypeObject sal_object_type = {
   0,				  /*tp_weaklistoffset */
   0,				  /*tp_iter */
   0,				  /*tp_iternext */
-  0,				  /*tp_methods */
+  sal_object_methods,		  /*tp_methods */
   0,				  /*tp_members */
   sal_object_getset		  /*tp_getset */
 };
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 5d72c34..ded9d94 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,14 @@
+2010-03-17  Phil Muldoon  <pmuldoon@redhat.com>
+
+	* gdb.python/Makefile.in: Add py-objfile.
+	* gdb.python/py-objfile.exp: New file.
+	* gdb.python/py-objfile.c: New file.
+	* gdb.python/py-block.exp: Add is_valid tests.
+	* gdb.python/py-inferior.exp: Ditto.
+	* gdb.python/py-infthread.exp: Ditto.
+	* gdb.python/py-symbol.exp: Ditto.
+	* gdb.python/py-symtab.exp: Ditto.
+
 2011-03-16  Keith Seitz  <keiths@redhat.com>
 
 	PR c++/12273
diff --git a/gdb/testsuite/gdb.python/Makefile.in b/gdb/testsuite/gdb.python/Makefile.in
index 2b26fc8..5b2b7b0 100644
--- a/gdb/testsuite/gdb.python/Makefile.in
+++ b/gdb/testsuite/gdb.python/Makefile.in
@@ -4,7 +4,7 @@ srcdir = @srcdir@
 EXECUTABLES = py-type py-value py-prettyprint py-template py-block \
 	py-symbol py-mi py-breakpoint py-inferior py-infthread \
 	py-shared python lib-types py-events py-evthreads py-frame \
-	py-pp-maint py-progspace py-section-script
+	py-pp-maint py-progspace py-section-script py-objfile
 
 MISCELLANEOUS = py-shared-sl.sl
 
diff --git a/gdb/testsuite/gdb.python/py-block.exp b/gdb/testsuite/gdb.python/py-block.exp
index c400df7..98b89d9 100644
--- a/gdb/testsuite/gdb.python/py-block.exp
+++ b/gdb/testsuite/gdb.python/py-block.exp
@@ -62,3 +62,20 @@ gdb_py_test_silent_cmd "python block = frame.block()" "Get Frame 2's block" 0
 gdb_test "python print block" "<gdb.Block object at $hex>" \
          "Check Frame 2's block not None"
 gdb_test "python print block.function" "main" "main block"
+
+
+# Test Block is_valid.  This must always be the last test in this
+# testcase as it unloads the object file.
+delete_breakpoints
+gdb_py_test_silent_cmd "python frame = gdb.selected_frame()" "Get Frame" 0
+gdb_py_test_silent_cmd "python block = frame.block()" "Get Frame block" 0
+gdb_py_test_silent_cmd "python block_iter = iter (block)" "Get Frame block" 0
+gdb_test "python print block.is_valid()" "True" \
+         "Check block validity"
+gdb_test "python print block_iter.is_valid()" "True" \
+         "Check block validity"
+gdb_unload
+gdb_test "python print block.is_valid()" "False" \
+         "Check block validity"
+gdb_test "python print block_iter.is_valid()" "False" \
+         "Check block validity"
diff --git a/gdb/testsuite/gdb.python/py-inferior.exp b/gdb/testsuite/gdb.python/py-inferior.exp
index 138c0fb..42ca920 100644
--- a/gdb/testsuite/gdb.python/py-inferior.exp
+++ b/gdb/testsuite/gdb.python/py-inferior.exp
@@ -191,3 +191,23 @@ if [isnative] {
     gdb_test "py print gdb.inferiors()\[0\].search_memory (start_addr, end_addr - start_addr, pattern)" \
       "${one_pattern_found}" "find pattern straddling chunk boundary"
 }
+
+# Test Inferior is_valid.  This must always be the last test in
+# this testcase as it kills the inferior.
+
+gdb_py_test_silent_cmd "python inf_list = gdb.inferiors()" "get initial list" 1
+gdb_test "python print len(inf_list)" "1" "Get inferior list length"
+gdb_test "python print inf_list\[0\].is_valid()" "True" \
+         "Check inferior validity"
+gdb_test "add-inferior" "Added inferior 2.*" "add empty inferior 2"
+gdb_py_test_silent_cmd "python inf_list = gdb.inferiors()" "get new list" 1
+gdb_test "python print len(inf_list)" "2" "Get inferior list length"
+gdb_test "python print inf_list\[0\].is_valid()" "True" \
+         "Check inferior validity"
+gdb_test "python print inf_list\[1\].is_valid()" "True" \
+         "Check inferior validity"
+gdb_test_no_output "remove-inferiors 2" "remove-inferiors 2"
+gdb_test "python print inf_list\[0\].is_valid()" "False" \
+         "Check inferior validity"
+gdb_test "python print inf_list\[1\].is_valid()" "True" \
+         "Check inferior validity"
diff --git a/gdb/testsuite/gdb.python/py-infthread.exp b/gdb/testsuite/gdb.python/py-infthread.exp
index bbec4ec..05539ae 100644
--- a/gdb/testsuite/gdb.python/py-infthread.exp
+++ b/gdb/testsuite/gdb.python/py-infthread.exp
@@ -64,3 +64,10 @@ gdb_test "python print gdb.selected_thread().name == name" "True" \
 gdb_test "python print 'result =', t0.is_stopped ()" " = True" "test InferiorThread.is_stopped"
 gdb_test "python print 'result =', t0.is_running ()" " = False" "test InferiorThread.is_running"
 gdb_test "python print 'result =', t0.is_exited ()" " = False" "test InferiorThread.is_exited"
+
+# Test InferiorThread is_valid.  This must always be the last test in
+# this testcase as it kills the inferior.
+
+gdb_test "python print 'result =', t0.is_valid ()" " = True" "test InferiorThread.is_valid"
+gdb_test_no_output "kill inferior 1" "kill inferior 1"
+gdb_test "python print 'result =', t0.is_valid ()" " = False" "test InferiorThread.is_valid"
diff --git a/gdb/testsuite/gdb.python/py-objfile.c b/gdb/testsuite/gdb.python/py-objfile.c
new file mode 100644
index 0000000..8add52c
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-objfile.c
@@ -0,0 +1,23 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2011 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int
+main ()
+{
+  int some_var = 0;
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.python/py-objfile.exp b/gdb/testsuite/gdb.python/py-objfile.exp
new file mode 100644
index 0000000..f86efb5
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-objfile.exp
@@ -0,0 +1,51 @@
+# Copyright (C) 2011 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This file is part of the GDB testsuite.  It tests the program space
+# support in Python.
+
+if $tracelevel then {
+    strace $tracelevel
+}
+
+load_lib gdb-python.exp
+
+set testfile "py-objfile"
+set srcfile ${testfile}.c
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
+    return -1
+}
+
+# Skip all tests if Python scripting is not enabled.
+if { [skip_python_tests] } { continue }
+
+if ![runto_main] then {
+    fail "Can't run to main"
+    return 0
+}
+
+gdb_py_test_silent_cmd "python sym = gdb.lookup_symbol(\"some_var\")" \
+    "Find a symbol in objfile" 1
+gdb_py_test_silent_cmd "python objfile = sym\[0\].symtab.objfile" \
+    "Get backing object file" 1
+
+gdb_test "python print objfile.filename" ".*py-objfile.*" \
+  "Get objfile validity"
+gdb_test "python print objfile.is_valid()" "True" \
+  "Get objfile validity"
+gdb_unload
+gdb_test "python print objfile.is_valid()" "False" \
+  "Get objfile validity after unload"
diff --git a/gdb/testsuite/gdb.python/py-symbol.exp b/gdb/testsuite/gdb.python/py-symbol.exp
index b30c639..bb22485 100644
--- a/gdb/testsuite/gdb.python/py-symbol.exp
+++ b/gdb/testsuite/gdb.python/py-symbol.exp
@@ -128,3 +128,19 @@ gdb_test "python print cplusfunc.name" "SimpleClass::valueofi().*" "Test func.na
 gdb_test "python print cplusfunc.print_name" "SimpleClass::valueofi().*" "Test func.print_name"
 gdb_test "python print cplusfunc.linkage_name" "SimpleClass::valueofi().*" "Test func.linkage_name"
 gdb_test "python print cplusfunc.addr_class == gdb.SYMBOL_LOC_BLOCK" "True" "Test func.addr_class"
+
+# Test is_valid when the objfile is unloaded.  This must be the last
+# test as it unloads the object file in GDB.
+# Start with a fresh gdb.
+clean_restart ${testfile}
+if ![runto_main] then {
+    fail "Cannot run to main."
+    return 0
+}
+gdb_breakpoint [gdb_get_line_number "Break at end."]
+gdb_continue_to_breakpoint "Break at end."
+gdb_py_test_silent_cmd "python a = gdb.lookup_symbol(\'a\')" "Get variable a" 0
+gdb_test "python print a\[0\].is_valid()" "True" "Test symbol validity"
+delete_breakpoints
+gdb_unload
+gdb_test "python print a\[0\].is_valid()" "False" "Test symbol validity"
diff --git a/gdb/testsuite/gdb.python/py-symtab.exp b/gdb/testsuite/gdb.python/py-symtab.exp
index d22811d..c52f5ef 100644
--- a/gdb/testsuite/gdb.python/py-symtab.exp
+++ b/gdb/testsuite/gdb.python/py-symtab.exp
@@ -57,8 +57,16 @@ gdb_py_test_silent_cmd "python symtab = sal.symtab" "Get block" 0
 gdb_test "python print sal.symtab" "gdb/testsuite/gdb.python/py-symbol.c.*" "Test symtab"
 gdb_test "python print sal.pc" "${decimal}" "Test sal.pc"
 gdb_test "python print sal.line" "42" "Test sal.line"
+gdb_test "python print sal.is_valid()" "True" "Test sal.is_valid"
 
 # Test symbol table.
 gdb_test "python print symtab.filename" "testsuite/gdb.python/py-symbol.c.*" "Test symtab.filename"
 gdb_test "python print symtab.objfile" "<gdb.Objfile object at ${hex}>" "Test symtab.objfile"
 gdb_test "python print symtab.fullname()" "testsuite/gdb.python/py-symbol.c.*" "Test symtab.fullname"
+gdb_test "python print symtab.is_valid()" "True" "Test symtab.is_valid()"
+
+# Test is_valid when the objfile is unloaded.  This must be the last
+# test as it unloads the object file in GDB.
+gdb_unload
+gdb_test "python print sal.is_valid()" "False" "Test sal.is_valid"
+gdb_test "python print symtab.is_valid()" "False" "Test symtab.is_valid()"