Re: PATCH [8/n]: Prepare x32: PR other/48007: Unwind library doesn't work with UNITS_PER_WORD > sizeof (void *)

["H.J. Lu" <hjl.tools@gmail.com>]

On Thu, Jun 30, 2011 at 8:03 AM, Jason Merrill <jason@redhat.com> wrote:
> On 06/30/2011 10:42 AM, H.J. Lu wrote:
>>
>> Register may be saved/restored either by address or value. My patch
>> doesn't change the reg field.  The other way will be
>>
>> #ifdef USE_UNWIND_WORD
>>     _Unwind_Word reg[DWARF_FRAME_REGISTERS+1];
>> #else
>>      void *reg[DWARF_FRAME_REGISTERS+1];
>> #endif
>>
>> We need it so that we are binary compatible with the existing
>> unwind context.  Once we do that we need many
>>
>> #ifdef USE_UNWIND_WORD
>> #endif
>>
>> whenever the reg field is accessed since the reg field is changed.
>
> But your patch already changes all but one place where reg is accessed.  And
> we can avoid lots of ifdefs by abstraction with macros/inlines so there's
> one interface.

I can do that.

> Also, why change SIGNAL_FRAME_BIT?
>

The current one is

  /* Signal frame context.  */
#define SIGNAL_FRAME_BIT ((~(_Unwind_Word) 0 >> 1) + 1)

It is defined such a strange way to be binary backward compatible.
Since there is no such a problem with if REG_VALUE_IN_UNWIND_CONTEXT
is defined, I simply define it as

  /* Signal frame context.  */
#define SIGNAL_FRAME_BIT ((_Unwind_Word) 1 >> 0)

Thanks.

-- 
H.J.