Re: The problems of PQhost()

On Thu, Nov 27, 2014 at 12:38 PM, Noah Misch <noah@leadboat.com> wrote:
> On Tue, Nov 25, 2014 at 09:53:10PM +0900, Fujii Masao wrote:
>> On Tue, Nov 25, 2014 at 12:37 PM, Noah Misch <noah@leadboat.com> wrote:
>> > On Wed, Jan 22, 2014 at 11:48:26PM +0900, Fujii Masao wrote:
>> >> (3) PQhost() cannot return the hostaddr.
>> >
>> >> We can fix the problem (3) by changing PQhost() so that it also
>> >> returns the hostaddr. But this change might break the existing
>> >> application using PQhost(). So, I added new libpq function PQhostaddr()
>> >> which returns the hostaddr, and changed \conninfo so that it reports
>> >> correct connection information by using both PQhost() and PQhostaddr().
>> >
>> >> +     <varlistentry id="libpq-pqhostaddr">
>> >> +      <term>
>> >> +       <function>PQhostaddr</function>
>> >> +       <indexterm>
>> >> +        <primary>PQhostaddr</primary>
>> >> +       </indexterm>
>> >> +      </term>
>> >> +
>> >> +      <listitem>
>> >> +       <para>
>> >> +        Returns the server numeric IP address or host name of the connection.
>> >> + <synopsis>
>> >> + char *PQhostaddr(const PGconn *conn);
>> >> + </synopsis>
>> >> +       </para>
>> >> +      </listitem>
>> >> +     </varlistentry>
>> >
>> > From reading this documentation, I assumed this function would return a
>> > non-empty value for every TCP connection.  After all, every TCP connection has
>> > a peer IP address.  In fact, PQhostaddr() returns the raw value of the
>> > "hostaddr" connection parameter, whether from a libpq function argument or
>> > from the PGHOSTADDR environment variable.  (If the parameter and environment
>> > variable are absent, it returns NULL.  Adding "hostaddr=" to the connection
>> > string makes it return the empty string.)  A caller wanting the specific raw
>> > value of a parameter could already use PQconninfo().  I suspect this new
>> > function will confuse more than help.  What do you think of reverting it and
>> > having \conninfo use PQconninfo() to discover any "hostaddr" value?
>>
>> Sounds reasonable to me. Are you planning to implement and commit the patch?
>
> Sure.  I'll first issue "git revert 9f80f48", then apply the attached patch.
> Since libpq ignores a hostaddr parameter equal to the empty string, this
> implementation does likewise.  Apart from that, I anticipate behavior
> identical to today's code.

+                fprintf(stderr, _("out of memory\n"));

psql_error() should be used instead of fprintf()?

+            if (host == NULL)    /* can't happen */

Is this comment true? ISTM that "host" can be NULL when the default socket
directory is used, i.e., neither host nor hostaddr are supplied by the user.

Regards,

-- 
Fujii Masao