RE: [PATCH v3 1/1] gdb/dwarf2: Fix 'rw_pieced_value' for values casted to different type.

["Rohr, Stephan" <stephan.rohr@intel.com>]

Hi Tom.

> -----Original Message-----
> From: Tom Tromey <tom@tromey.com>
> Sent: Thursday, January 5, 2023 8:53 PM
> To: Stephan Rohr via Gdb-patches <gdb-patches@sourceware.org>
> Cc: Rohr, Stephan <stephan.rohr@intel.com>
> Subject: Re: [PATCH v3 1/1] gdb/dwarf2: Fix 'rw_pieced_value' for values
> casted to different type.
> 
> >>>>> Stephan Rohr via Gdb-patches <gdb-patches@sourceware.org>
> writes:
> 
> > From: "Rohr, Stephan" <stephan.rohr@intel.com> The 'rw_pieced_value'
> > function is executed when fetching a (lazy) variable described by
> > 'DW_OP_piece' or 'DW_OP_bit_piece'.  The function checks the 'type'
> > and 'enclosing_type' fields of the value for identity.
> 
> Thanks for the patch.
> 
> > If a lazy value is fetched, GDB allocates space based on the enclosing
> > type's length and typically reads the 'full' object.  This is not
> > implemented for pieced values and causes an internal error if 'type'
> > and 'enclosing_type' of a value are not identical.
> 
> > However, GDB can read the value based on its type.  Thus, this patch
> > fixes the previously mentioned cases by removing the check for identity.
> 
> I thought there was some other discussion & idea about the cause of this
> patch... something like, setting a value's type should reset the enclosing
> type?  Or vice versa?  I am wondering if you tried this approach instead.
> 
> Tom

There was a discussion with Simon whether the value cast should update the
enclosing type.  Simon tried it out but as I understood he's also not clear on
what the right answer answers are.  From my point of view, this would also
be a separate patch.

Thanks
Stephan
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