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

[Paul Koning <paulkoning@comcast.net>]

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