[RFA] Fix PR python/19438, PR python/18393 - initialize dictionaries

[Tom Tromey <tom at tromey dot com>]

This fixes PR python/19438 and PR python/18393.  Both bugs are about
invoking dir() on some Python object implemented by gdb, and getting a
crash.

The crash happens because the dictionary field of these objects was
not initialized.  Apparently what happens is that this field can be
lazily initialized by Python when assigning to an attribute; and it
can also be handled ok when using dir() but without __dict__ defined;
but gdb defines __dict__ because this isn't supplied automatically by
Python.

The docs on this seem rather sparse, but this patch works ok.

An alternative might be to lazily create the dictionary in
gdb_py_generic_dict, but I went with this approach because it seemed
more straightforward.

Built and regtested on x86-64 Fedora 23.

2016-05-18  Tom Tromey  <tom@tromey.com>

	PR python/19438, PR python/18393:
	* python/py-objfile.c (objfpy_initialize): Initialize self->dict.
	* python/py-progspace.c (pspy_initialize): Initialize self->dict.

2016-05-18  Tom Tromey  <tom@tromey.com>

	PR python/19438, PR python/18393:
	* gdb.python/py-progspace.exp: Add "dir" test.
	* gdb.python/py-objfile.exp: Add "dir" test.
---
 gdb/ChangeLog                             | 6 ++++++
 gdb/python/py-objfile.c                   | 5 ++++-
 gdb/python/py-progspace.c                 | 5 ++++-
 gdb/testsuite/ChangeLog                   | 6 ++++++
 gdb/testsuite/gdb.python/py-objfile.exp   | 2 ++
 gdb/testsuite/gdb.python/py-progspace.exp | 2 ++
 6 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 92024b6..7da1385 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2016-05-18  Tom Tromey  <tom@tromey.com>
 
+	PR python/19438, PR python/18393:
+	* python/py-objfile.c (objfpy_initialize): Initialize self->dict.
+	* python/py-progspace.c (pspy_initialize): Initialize self->dict.
+
+2016-05-18  Tom Tromey  <tom@tromey.com>
+
 	* rust-lang.c (rust_subscript): Initialize "high".
 
 2016-05-17  Simon Marchi  <simon.marchi@ericsson.com>
diff --git a/gdb/python/py-objfile.c b/gdb/python/py-objfile.c
index cd26c5b..82df4b2 100644
--- a/gdb/python/py-objfile.c
+++ b/gdb/python/py-objfile.c
@@ -196,7 +196,10 @@ static int
 objfpy_initialize (objfile_object *self)
 {
   self->objfile = NULL;
-  self->dict = NULL;
+
+  self->dict = PyDict_New ();
+  if (self->dict == NULL)
+    return 0;
 
   self->printers = PyList_New (0);
   if (self->printers == NULL)
diff --git a/gdb/python/py-progspace.c b/gdb/python/py-progspace.c
index e1258c7..6fc53cb 100644
--- a/gdb/python/py-progspace.c
+++ b/gdb/python/py-progspace.c
@@ -97,7 +97,10 @@ static int
 pspy_initialize (pspace_object *self)
 {
   self->pspace = NULL;
-  self->dict = NULL;
+
+  self->dict = PyDict_New ();
+  if (self->dict == NULL)
+    return 0;
 
   self->printers = PyList_New (0);
   if (self->printers == NULL)
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index a773c63..c813436 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2016-05-18  Tom Tromey  <tom@tromey.com>
+
+	PR python/19438, PR python/18393:
+	* gdb.python/py-progspace.exp: Add "dir" test.
+	* gdb.python/py-objfile.exp: Add "dir" test.
+
 2016-05-18  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* gdb.mi/mi-threads-interrupt.c: New file.
diff --git a/gdb/testsuite/gdb.python/py-objfile.exp b/gdb/testsuite/gdb.python/py-objfile.exp
index 1bbb4cf..62ca309 100644
--- a/gdb/testsuite/gdb.python/py-objfile.exp
+++ b/gdb/testsuite/gdb.python/py-objfile.exp
@@ -45,6 +45,8 @@ gdb_test "python print (objfile.filename)" "${testfile}" \
 gdb_test "python print (objfile.username)" "${testfile}" \
   "Get objfile user name"
 
+gdb_test_no_output "python dir(objfile)"
+
 gdb_test "python print (gdb.lookup_objfile (\"${testfile}\").filename)" \
     "${testfile}" "print lookup_objfile filename"
 gdb_test "python print (gdb.lookup_objfile (\"junk\"))" \
diff --git a/gdb/testsuite/gdb.python/py-progspace.exp b/gdb/testsuite/gdb.python/py-progspace.exp
index 5c1db1c..396d0f2 100644
--- a/gdb/testsuite/gdb.python/py-progspace.exp
+++ b/gdb/testsuite/gdb.python/py-progspace.exp
@@ -37,6 +37,8 @@ gdb_test "python print (gdb.current_progspace().filename)" "None" \
   "current progspace filename (None)"
 gdb_test "python print (gdb.progspaces())" "\\\[<gdb.Progspace object at $hex>\\\]"
 
+gdb_test_no_output "python dir(gdb.current_progspace())"
+
 gdb_load ${binfile}
 
 gdb_py_test_silent_cmd "python progspace = gdb.current_progspace()" \
-- 
2.5.5