Re: [PATCH v2] gdbserver: dump 'xx...x' in collect_register_as_string for unavailable register

[Luis Machado <luis.machado@arm.com>]

Hi,

On 11/21/23 19:53, Aktemur, Tankut Baris wrote:
> Kindly pinging.
> 
> Regards
> -Baris
> 
> On Tuesday, June 20, 2023 5:55 PM, Aktemur, Tankut Baris wrote:
>> Fix 'collect_register_as_string' so that unavailable registers are
>> dumped as 'xx...x' instead of arbitrary values.  This gives the
>> opportunity that we can reuse 'collect_register_as_string' in
>> 'registers_to_string' for additional code simplification.
>> ---
>>  gdbserver/regcache.cc | 26 +++++++++++---------------
>>  1 file changed, 11 insertions(+), 15 deletions(-)
>>
>> diff --git a/gdbserver/regcache.cc b/gdbserver/regcache.cc
>> index 0b1141662ac..c0a6d6eb0a4 100644
>> --- a/gdbserver/regcache.cc
>> +++ b/gdbserver/regcache.cc
>> @@ -210,24 +210,13 @@ find_register_by_number (const struct target_desc *tdesc, int
>> n)
>>  void
>>  registers_to_string (struct regcache *regcache, char *buf)
>>  {
>> -  unsigned char *registers = regcache->registers;
>>    const struct target_desc *tdesc = regcache->tdesc;
>>
>>    for (int i = 0; i < tdesc->reg_defs.size (); ++i)
>>      {
>> -      if (regcache->register_status[i] == REG_VALID)
>> -	{
>> -	  bin2hex (registers, buf, register_size (tdesc, i));
>> -	  buf += register_size (tdesc, i) * 2;
>> -	}
>> -      else
>> -	{
>> -	  memset (buf, 'x', register_size (tdesc, i) * 2);
>> -	  buf += register_size (tdesc, i) * 2;
>> -	}
>> -      registers += register_size (tdesc, i);
>> +      collect_register_as_string (regcache, i, buf);
>> +      buf += register_size (tdesc, i) * 2;
>>      }
>> -  *buf = '\0';
>>  }
>>
>>  void
>> @@ -472,8 +461,15 @@ regcache_raw_get_unsigned_by_name (struct regcache *regcache,
>>  void
>>  collect_register_as_string (struct regcache *regcache, int n, char *buf)
>>  {
>> -  bin2hex (register_data (regcache, n), buf,
>> -	   register_size (regcache->tdesc, n));
>> +  int reg_size = register_size (regcache->tdesc, n);
>> +
>> +  if (regcache->register_status[n] == REG_VALID)
>> +    bin2hex (register_data (regcache, n), buf, reg_size);
>> +  else
>> +    memset (buf, 'x', reg_size * 2);
>> +
>> +  buf += reg_size * 2;
>> +  *buf = '\0';
>>  }

I don't mind this improvement, but I was wondering if using the std::string variant of bin2hex would
allow further simplification of this code. You wouldn't have to handle the \0 explicitly.

I guess the slightly confusing part is that collect_register_as_string finishes the string with \0,
but registers_to_string ignores it and overwrites it.

In any case, I think this is a nice improvement.

Reviewed-By:  Luis Machado  <luis.machado@arm.com>

>>
>>  void
>> --
>> 2.25.1