Re: Python: fetch value when building gdb.Value object [rediff]

Paul Koning
2011-10-01T18:58:39Z

On Oct 1, 2011, at 8:16 AM, Jan Kratochvil wrote:

> Updated for current HEAD:
>
> On Sat, 01 Oct 2011 11:28:52 +0200, Jan Kratochvil wrote:
> On Wed, 28 Sep 2011 21:24:45 +0200, Phil Muldoon wrote:
>> What scenario will this test catch that the previous test won't? I'm
>> not saying you are incorrect, I just don't understand. What
>> error-trigger does the assignment to "inval" trigger?
>
> I would prefer here a testcase more clearly showing the bug, attached below.

Thanks, yes I agree that's a clearer and more complete testcase.

paul

>
> I believe the patch is right, as Phil hasn't yet agreed posting it only.
>
>
> Thanks,
> Jan
>
>
> gdb/
> 2011-09-21 Paul Koning <paul_koning@dell.com>
>
> * python/py-value.c (valpy_get_address): Use Py_XINCREF.
> (value_to_value_object): Fetch value if it was lazy.
>
> testsuite/
> 2011-09-21 Paul Koning <paul_koning@dell.com>
> Jan Kratochvil <jan.kratochvil@redhat.com>
>
> * gdb.python/py-value.exp
> (python inval = gdb.parse_and_eval('*(int*)0'))
> (python argc_lazy = gdb.parse_and_eval('argc'), sanity check argc)
> (set argc=2, python print argc_lazy): New tests.
>
> --- a/gdb/python/py-value.c
> +++ b/gdb/python/py-value.c
> @@ -209,7 +209,7 @@ valpy_get_address (PyObject *self, void *closure)
> val_obj->address = value_to_value_object (res_val);
> }
>
> - Py_INCREF (val_obj->address);
> + Py_XINCREF (val_obj->address);
>
> return val_obj->address;
> }
> @@ -1045,7 +1045,15 @@ PyObject *
> value_to_value_object (struct value *val)
> {
> value_object *val_obj;
> + volatile struct gdb_exception except;
>
> + TRY_CATCH (except, RETURN_MASK_ALL)
> + {
> + if (value_lazy (val))
> + value_fetch_lazy (val);
> + }
> + GDB_PY_HANDLE_EXCEPTION (except);
> +
> val_obj = PyObject_New (value_object, &value_object_type);
> if (val_obj != NULL)
> {
> --- a/gdb/testsuite/gdb.python/py-value.exp
> +++ b/gdb/testsuite/gdb.python/py-value.exp
> @@ -236,6 +236,18 @@ proc test_value_in_inferior {} {
> gdb_test "python print gdb.parse_and_eval('*(int*)0')" "gdb.MemoryError: Cannot access memory at address 0x0.*" $test
> }
>
> + # Test Python values are not lazy.
> + set test "memory error occurs even for possibly lazy values"
> + if {$can_read_0} {
> + untested $test
> + } else {
> + gdb_test "python inval = gdb.parse_and_eval('*(int*)0')" "gdb.MemoryError: Cannot access memory at address 0x0.*" $test
> + }
> + gdb_test "python argc_lazy = gdb.parse_and_eval('argc')"
> + gdb_test "print argc" " = 1" "sanity check argc"
> + gdb_test_no_output "set argc=2"
> + gdb_test "python print argc_lazy" "\r\n1"
> +
> # Test string fetches, both partial and whole.
> gdb_test "print st" "\"divide et impera\""
> gdb_py_test_silent_cmd "python st = gdb.history (0)" "get value from history" 1