Patch to "configure" to enable PostgreSQL build with Kerberos 5 on Solaris 11

Included below are extracts from an earlier email thread (on
pgsql-ports) discussing the problem.

Attached are the context diffs for configure.in.

This change has no impact unless the "--with-krb5" option is used with
"configure". If the option *is* used, configure will now only search for
function krb5_sendauth(), instead of looking for both krb5_encrypt() and
krb5_sendauth().

I've tested (i.e. built using --with-krb5) with version 8.1.4 on Solaris
11 only. This change should have no negative impact for builds on other
platforms since:

a) The check for krb5_sendauth() remains, which is sufficient to
determine the presence of Kerberos 5

and

b) None of the PostgreSQL code uses krb5_encrypt() anyway

James Gates wrote:
> Prior to Solaris 11 (Nevada), the full Kerberos 5 API was never exposed
> (only the gss interface), so building PostgreSQL with the "--with-krb5"
> option is a problem.
>
> In Nevada, Sun has exposed the full MIT Kerberos 5 API (v1.4.0). So
> building PostgreSQL with Kerberos should be possible/easy. If I try to
> build 8.1.4 though, it fails with the following error:
>
> $ ./configure --with-krb5 --without-readline
> checking build system type... sparc-sun-solaris2.11
> checking host system type... sparc-sun-solaris2.11
> ... snip ...
> checking for library containing com_err... -lkrb5
> checking for library containing krb5_encrypt... no
> configure: error: could not find function 'krb5_encrypt' required for
> Kerberos 5
>
> This is because in krb5 v1.4.0, the krb5_encrypt() function is
> deprecated/removed, so doesn't exist anywhere in the Solaris libraries.
> It is replaced by krb5_c_encrypt() (I think this change occurred
> sometime between krb5 v1.2.1 and v1.4.0)
>
> But looking more closely at the PostgreSQL 8.1.4 code, I see that it
> never even uses the krb5_encrypt() function anyway! So although it's
> presence might be a useful method for detecting the presence of Kerberos
> 5 (pre v1.4.0), it seems unnecessary for the successful operation of
> PostgreSQL.
>
> By simply removing the check for krb5_encrypt() from the configure
> script, I can successfully build PostgreSQL with krb5 on Nevada.
>
> Does anyone know why the check for krb5_encrypt() exists in configure
> when the code doesn't use it? And would absence of a good reason
> indicate this is a bug (and the check should be removed)?

Tom Lane wrote:
> James Gates <James(dot)Gates(at)Sun(dot)COM> writes:
>> Does anyone know why the check for krb5_encrypt() exists in configure
>> when the code doesn't use it?
>
> At the time it was chosen, it was probably a reasonable choice of
> function to probe for to make sure Kerberos libraries are present.
> Do you have a better suggestion?
>
> regards, tom lane

James Gates wrote:
> The configure script already checks for krb5_sendauth() as well as
> krb5_encrypt(). The libpq code *does* use krb5_sendauth(), which is not
> deprecated (and I know of no plans to make it so).
>
> I discussed this problem last night with Magnus Hagander, and we're both
> of the opinion that the search for krb5_sendauth() alone is sufficient
> to determine if krb5 is present on your system.
>
> Magus suspects that at some point in the past, PostgreSQL did use
> krb5_encrypt(), and it was changed (maybe in anticipation of the
> function becoming deprecated?). Whoever made the change,
> forgot/neglected to remove the check from the configure script.
>
> I propose that we remove the check for krb5_encrypt() from the configure
> script, leaving just the check for krb5_sendauth().
>
> Note - krb5_encrypt() is replaced by krb5_c_encrypt() in the latest
> implementation of krb5. We could change the configure script to check
> for this as well, but as mentioned above, I think this is unnecessary.