Re: [PATCH 1/3] fix crash in frame filters

[Phil Muldoon <pmuldoon at redhat dot com>]

On Wed, 22 Jan 2014, Tom Tromey wrote:

> apply_frame_filter calls ensure_python_env before computing the
> gdbarch to use.  This means that python_gdbarch can be NULL while in
> Python code, and if a frame filter depends on this somehow (easy to
> do), gdb will crash.
> 
> The fix is to compute the gdbarch first.
> 
> Built and regtested on x86-64 Fedora 18.
> New test case included.
> 
> 2014-01-22  Tom Tromey  <tromey@redhat.com>
> 
> 	PR python/16491:
> 	* python/py-framefilter.c (apply_frame_filter): Call
> 	ensure_python_env after computing gdbarch.
> 
> 2014-01-22  Tom Tromey  <tromey@redhat.com>
> 
> 	PR python/16491:
> 	* gdb.python/py-framefilter.py (Reverse_Function.function): Read a
> 	string from an inferior frame.
> 	* gdb.python/py-framefilter-mi.exp: Update.

These are all fine, and thanks for fixing them.  I think they should
proceed into 7.7 too.  Especially this one:

> diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
> index 76ce4e5..c6a29ef 100644
> --- a/gdb/python/py-framefilter.c
> +++ b/gdb/python/py-framefilter.c
> @@ -1477,18 +1477,18 @@ apply_frame_filter (struct frame_info *frame, int flags,
>    if (!gdb_python_initialized)
>      return PY_BT_NO_FILTERS;
>  
> -  cleanups = ensure_python_env (gdbarch, current_language);
> -
>    TRY_CATCH (except, RETURN_MASK_ALL)
>      {
>        gdbarch = get_frame_arch (frame);
>      }
>    if (except.reason < 0)
>      {
> -      gdbpy_convert_exception (except);
> -      goto error;
> +      /* Let gdb try to print the stack trace.  */
> +      return PY_BT_NO_FILTERS;
>      }
>  
> +  cleanups = ensure_python_env (gdbarch, current_language);
> +

Ugh ugly. Ssing gdbarch when it is NULL before querying the frame for an
architecture is especially clumsy.  :( mea culpa.

Cheers,

Phil