Re: [PATCH 1/2] gdb/alpha: Add target description support

[Yodel Eldar <yodel.eldar@gmail.com>]

On 6/3/25 1:49 PM, Simon Marchi wrote:
> On 5/26/25 11:12 AM, Yodel Eldar wrote:
>> @@ -1715,11 +1696,39 @@ alpha_software_single_step (struct regcache *regcache)
>>   static struct gdbarch *
>>   alpha_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
>>   {
>> +  tdesc_arch_data_up tdesc_data;
>> +  const struct target_desc *tdesc = info.target_desc;
>> +
>>     /* Find a candidate among extant architectures.  */
>>     arches = gdbarch_list_lookup_by_info (arches, &info);
>>     if (arches != NULL)
>>       return arches->gdbarch;
>>   
>> +  if (tdesc == nullptr)
>> +    tdesc = tdesc_alpha;
>> +
>> +  /* Validate target description.  */
>> +  if (tdesc_has_registers (tdesc))
>> +    {
>> +      const struct tdesc_feature *feature;
>> +      bool valid_p;
>> +
>> +      feature = tdesc_find_feature (tdesc, "org.gnu.gdb.alpha.core");
>> +      if (feature == nullptr)
>> +	return nullptr;
>> +
>> +      tdesc_data = tdesc_data_alloc ();
>> +      valid_p = true;
>> +      for (int i = 0; i < ALPHA_NUM_REGS; ++i)
>> +	valid_p &= tdesc_numbered_register (feature, tdesc_data.get (), i,
>> +					    alpha_register_names[i]);
>> +
>> +      if (!valid_p)
>> +	return nullptr;
> Do we need to call tdesc_numbered_register for the register whose name
> is ""?  I suppose that we do, for backwards compatibility, when
> debugging against a remote target that doesn't send a target
> description?
>
> Simon


Hi Simon and thanks for your time and question! I think we do, because
(IIUC) suppose an older remote target responds to, say, a 'p n' packet,
but the anonymous register is unaccounted for by the client, wouldn't
that break compatibility? Can't say for certain, so I defer to your and
the community's wisdom and err on the side of caution as I investigate
it.

Yodel