[patch] [python] Fix for double-free.

[patch] [python] Fix for double-free.

[Paul Pluzhnikov]

Greetings,

I made the change below on archer-tromey-python.

Unfortunately, I can't seem to be able to construct a test case
which exposes this bug.

OK to commit without a test case?

Thanks,
--
Paul Pluzhnikov

2008-10-23  Paul Pluzhnikov  <ppluzhnikov@google.com>
    
    * python/python-value (valpy_getitem): Fix heap corruption.
    
diff --git a/gdb/python/python-value.c b/gdb/python/python-value.c
index 93af465..5064ccf 100644
--- a/gdb/python/python-value.c
+++ b/gdb/python/python-value.c
@@ -209,7 +209,8 @@ valpy_getitem (PyObject *self, PyObject *key)
 
   TRY_CATCH (except, RETURN_MASK_ALL)
     {
-      res_val = value_struct_elt (&self_value->value, NULL, field, 0, NULL);
+      struct value *tmp = self_value->value;
+      res_val = value_struct_elt (&tmp, NULL, field, 0, NULL);
     }
   GDB_PY_HANDLE_EXCEPTION (except);
 

Re: [patch] [python] Fix for double-free.

[Pedro Alves]

I'll take this one.

On Thursday 23 October 2008 18:21:58, Paul Pluzhnikov wrote:
> Greetings,
> 
> I made the change below on archer-tromey-python.
> 

Thanks for sending it here.

((((  When I asked before please to send breakage fixes here, I was
refering to breakages that affected everybody's non-python GDB usage, like
the build breakage of the other thread.  It's certainly nice to have the
code maintained though, in case people are already trying simple
things out.  Thanks again.  ))))

> Unfortunately, I can't seem to be able to construct a test case
> which exposes this bug.
> 

Weird.  Maybe the fact that you can't trigger it in FSF has something
to do with owned_by_gdb not being anywhere?  That's strange, because one
would expect to see a double-free then anyway, I guess.  Still, with
that in mind, the patch looks correct to me, though.

> OK to commit without a test case?

IMO, yes.  I'm sure you'll have testcases that trigger this when
more of the python stuff is in.

> Thanks,
> --
> Paul Pluzhnikov
> 
> 2008-10-23  Paul Pluzhnikov  <ppluzhnikov@google.com>
>     
>     * python/python-value (valpy_getitem): Fix heap corruption.
>     

-- 
Pedro Alves

Re: [patch] [python] Fix for double-free.

[Paul Pluzhnikov]

On Thu, Oct 23, 2008 at 12:15 PM, Pedro Alves <pedro@codesourcery.com> wrote:

>> OK to commit without a test case?
>
> IMO, yes.  I'm sure you'll have testcases that trigger this when
> more of the python stuff is in.

I *do* already have a test case which shows the bug on the branch.
Committed as above.

Thanks,
-- 
Paul Pluzhnikov