[PATCH] Do not expose stub types to Python

[Tom Tromey <tromey at adacore dot com>]

dwarf2read.c will create stub types for Ada "Taft Amendment" types.
These stub types can currently be exposed to Python code, where they
show up as TYPE_CODE_VOID types (but that, mysteriously, can sometimes
be used in other ways).

While it's possible to work with such types by using strip_typedefs,
this seemed unpleasant to me.  This patch takes another approach
instead, which is to try not to expose stub types to Python users.

gdb/ChangeLog
2019-08-22  Tom Tromey  <tromey@adacore.com>

	* python/py-type.c (type_to_type_object): Call check_typedef
	for stub types.

gdb/testsuite/ChangeLog
2019-08-22  Tom Tromey  <tromey@adacore.com>

	* gdb.ada/py_taft.exp: New file.
	* gdb.ada/py_taft/main.adb: New file.
	* gdb.ada/py_taft/pkg.adb: New file.
	* gdb.ada/py_taft/pkg.ads: New file.
---
 gdb/ChangeLog                          |  5 ++++
 gdb/python/py-type.c                   | 11 ++++++++
 gdb/testsuite/ChangeLog                |  7 +++++
 gdb/testsuite/gdb.ada/py_taft.exp      | 38 ++++++++++++++++++++++++++
 gdb/testsuite/gdb.ada/py_taft/main.adb | 22 +++++++++++++++
 gdb/testsuite/gdb.ada/py_taft/pkg.adb  | 27 ++++++++++++++++++
 gdb/testsuite/gdb.ada/py_taft/pkg.ads  | 22 +++++++++++++++
 7 files changed, 132 insertions(+)
 create mode 100644 gdb/testsuite/gdb.ada/py_taft.exp
 create mode 100644 gdb/testsuite/gdb.ada/py_taft/main.adb
 create mode 100644 gdb/testsuite/gdb.ada/py_taft/pkg.adb
 create mode 100644 gdb/testsuite/gdb.ada/py_taft/pkg.ads

diff --git a/gdb/python/py-type.c b/gdb/python/py-type.c
index e8af6f60e1e..134f76dafb0 100644
--- a/gdb/python/py-type.c
+++ b/gdb/python/py-type.c
@@ -1334,6 +1334,17 @@ type_to_type_object (struct type *type)
 {
   type_object *type_obj;
 
+  try
+    {
+      /* Try not to let stub types leak out to Python.  */
+      if (TYPE_STUB (type))
+	type = check_typedef (type);
+    }
+  catch (...)
+    {
+      /* Just ignore failures in check_typedef.  */
+    }
+
   type_obj = PyObject_New (type_object, &type_object_type);
   if (type_obj)
     set_type (type_obj, type);
diff --git a/gdb/testsuite/gdb.ada/py_taft.exp b/gdb/testsuite/gdb.ada/py_taft.exp
new file mode 100644
index 00000000000..71ac3327380
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/py_taft.exp
@@ -0,0 +1,38 @@
+# Copyright 2019 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/>.
+
+load_lib "ada.exp"
+load_lib gdb-python.exp
+
+standard_ada_testfile main
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable debug] != ""} {
+    return -1
+}
+
+clean_restart ${testfile}
+
+# Skip this testcase if Python scripting is not enabled.
+if { [skip_python_tests] } { continue }
+
+set bp_location [gdb_get_line_number "STOP" ${testdir}/main.adb]
+runto "main.adb:$bp_location"
+
+gdb_test_no_output "python v = gdb.parse_and_eval('v')"
+
+gdb_test "python print(v.dereference().type.code is gdb.TYPE_CODE_VOID)" \
+    "False"
+gdb_test "python print(v.type.strip_typedefs().target().code is gdb.TYPE_CODE_VOID)" \
+    "False"
diff --git a/gdb/testsuite/gdb.ada/py_taft/main.adb b/gdb/testsuite/gdb.ada/py_taft/main.adb
new file mode 100644
index 00000000000..b0ba8bdb90e
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/py_taft/main.adb
@@ -0,0 +1,22 @@
+--  Copyright 2019 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/>.
+
+with Pkg;
+
+procedure Main is
+   V : Pkg.Value := Pkg.Create (42);
+begin
+   null;				--  STOP
+end Main;
diff --git a/gdb/testsuite/gdb.ada/py_taft/pkg.adb b/gdb/testsuite/gdb.ada/py_taft/pkg.adb
new file mode 100644
index 00000000000..94ce4b1e851
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/py_taft/pkg.adb
@@ -0,0 +1,27 @@
+--  Copyright 2019 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/>.
+
+package body Pkg is
+
+   type Value_Record is record
+      I : Integer;
+   end record;
+
+   function Create (I : Integer) return Value is
+   begin
+      return new Value_Record'(I => I);
+   end Create;
+
+end Pkg;
diff --git a/gdb/testsuite/gdb.ada/py_taft/pkg.ads b/gdb/testsuite/gdb.ada/py_taft/pkg.ads
new file mode 100644
index 00000000000..daa4edbf1b1
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/py_taft/pkg.ads
@@ -0,0 +1,22 @@
+--  Copyright 2019 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/>.
+
+package Pkg is
+   type Value is private;
+   function Create (I : Integer) return Value;
+private
+   type Value_Record;
+   type Value is access all Value_Record;
+end Pkg;
-- 
2.20.1