Hi Tim--

Thanks for this new version of libpsl!

On Thu 2018-02-22 10:31:24 +0100, Tim Rühsen wrote:
>  this release comes with a new function flag PSL_TYPE_NO_STAR_RULE to be
>  used with psl_is_public_suffix2().
>  It disables the PSL 'prevailing star rule' and thus returns false for
>  TLDs that are not explicitly listed in the PSL.
>  The new flag makes only sense in combination with either PSL_TYPE_ANY,

Layering in this flag on the "type" argument makes the API tougher to
reason about than i was expecting.  I'm trying to follow the logic in
the implementation, but i think i might be missing it.

there are tests in psl.c that compare type directly to PSL_TYPE_ICANN,
without necessarily stripping off any extra flag bits:


                        /* check for correct rule type */
                        if (type == PSL_TYPE_ICANN && !(rc & _PSL_FLAG_ICANN))
                                goto suffix_no;
                        else if (type == PSL_TYPE_PRIVATE && !(rc & 
                                goto suffix_no;

                        if (rc & _PSL_FLAG_EXCEPTION)
                                goto suffix_no;

I note that type hasn't been touched at this point (unless
suffix.nlabels == 1, which isn't always the case).  These == comparisons
are guaranteed to fail if you treat type as a bitfield and more than one
bit is set :( Am i missing something?

Come to think of it, i don't know how this would work with PSL_TYPE_ANY
either -- can you explain that to me?

Maybe the test suite needs to be augmented to test this more rigorously.
I note that the live PSL has several entries with * rules with multiple
suffix labels, which might be useful to test against.  here are three
that might be interesting test cases:

  - *.nom.br
  - *.sch.uk
  - *.compute.amazonaws.com

> 22.02.2018 Release V0.20.0
>   * Remove hard-coded gcc flag in Makefile.am
>   * Prevent excessive CPU cycles on large inputs
>   * New flag PSL_TYPE_NO_STAR_RULE to skip star rule

this release appears to update LIBPSL_SO_VERSION like so:


This results in libpsl.so.6, when before it was libpsl.so.5.  but i
don't see how this makes sense. :/

Following the instructions in configure.ac for updating
current:revision:age i don't even see how it's possible to arrive at
8:0:2.  It looks like you took steps 3 and 4, but missed steps 5 and 6:

  5. If any interfaces have been added since the last public release, then 
increment age.
  6. If any existing interfaces have been removed or changed since the last 
public release, then set age to 0. 

I wish SONAME management was less confusing!

If you think that the inclusion of this flag warrants an SONAME bump
(i.e., steps 5 and 6 were triggered), then LIBPSL_SO_VERSION should be
8:0:0 (resulting in libpsl.so.8, and triggering a rebuild of all tools
against this new package).

But if you think the changes of this version do not warrant an SONAME
bump (i.e. only step 5 was triggered), then LIBPSL_SO_VERSION should be
8:0:3 (resulting in sticking with libpsl.so.5, and no recompilation

There's a caveat here -- some package could be built against a newer
version of libpsl.so.5, knowing about the flag, and then it could be
transferred to a machine with an older version of libpsl.so.5 that
*doesn't* know about the flag.

I don't think any older versions of libpsl check whether any of the
unknown bits in type are set (though as you can see above, i don't grok
the logic here very well), which means that older versions might
silently ignore this new flag.  If another tool is depending on the flag
having the intended effect, they could get in trouble if they're
transferred to a machine with an older version of libpsl.so.5.  But an
soname bump is a pretty heavyweight tool just for adding a flag.

Let me know what you think we should dohere.  I'm reluctant to include
this version in debian without sorting out both of these concerns, but
if you've got a plan for making them make sense, i'd be happy to think
it through with you.

all the best,


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