Re: [PATCH 2/3] inet: Remove strdupa from nrl_domainname()

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 11/11/2021 05:18, Florian Weimer wrote:
> * Adhemerval Zanella via Libc-alpha:
> 
>> We can use the already in place scratch_buffer.
>>
>> Checked on x86_64-linux-gnu.
>> ---
>>  inet/getnameinfo.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/inet/getnameinfo.c b/inet/getnameinfo.c
>> index 58ebbb1154..69a94604bd 100644
>> --- a/inet/getnameinfo.c
>> +++ b/inet/getnameinfo.c
>> @@ -127,10 +127,10 @@ nrl_domainname (void)
>>  	  else
>>  	    {
>>  	      /* We need to preserve the hostname.  */
>> -	      const char *hstname = strdupa (tmpbuf.data);
>> -	      while (__gethostbyname_r (hstname, &th,
>> -					tmpbuf.data,
>> -					tmpbuf.length,
>> +	      size_t hstnamelen = strlen (tmpbuf.data) + 1;
>> +	      while (__gethostbyname_r (tmpbuf.data, &th,
>> +					tmpbuf.data + hstnamelen,
>> +					tmpbuf.length - hstnamelen,
>>  					&h, &herror))
>>  		{
>>  		  if (herror == NETDB_INTERNAL && errno == ERANGE)
> 
> Can you use malloc instead?  scratch_buffer_grow_preserve is a bit of an
> outlier in the interface.

It would require to add more complexity, since now we have two allocations
to handle (the hstname and the scratch_buffer) and on fast patch it would
actually require a malloc call, where mostly likely it would be done in
the stack fror scratch_buffer.  I am not sure it is really an improvement
here.