[PATCH COMMITTED] Switch IDNA implementation to libidn2 [BZ #19728] [BZ #19729] [BZ #22247]

[Florian Weimer]

On 05/23/2018 07:51 PM, Adhemerval Zanella wrote:

> So in this case we should at least document this better, commit message does
> not have anything regarding it and NEWS update just states "[...] libidn2
> version 2.0.5 or later is recommended. [...]" which does not really state
> why 2.0.5 is preferred.

I thought that obvious: It has fewer bugs.  This dragged on for so many 
months because we kept finding issues that needed addressing, and only 
with the 2.0.5 release, we have something that is close both to the 
WHATWG recommendations (which isn't what browsers implement) and what is 
needed on some enterprise networks.

HJ tested with Fedora 28 libidn2 which has backports, so he reported 
only comparatively few test failures.

> Also, reading the newer tests does give any indication why 2.0.5 is required
> to fully compliance nor they check libidn2 version.  To one involved in glibc
> developments it should be straightforward to relate possible test-suite to
> related error, but I still think that indicating that system tests libidn is
> the culprit nor glibc itself is a better error output.

There are comments in the test case which indicate what is being tested 
(non-transitional mode, Unicode TR 46 mode).  These are areas where we 
pushed libidn2 to change defaults.

Due to the backports from some distributions, mentioning specific 
libidn2 versions could be misleading.

Immediately after the commit, I added a note 
<https://sourceware.org/glibc/wiki/Release/2.28#libidn2_is_a_recommended_dependency>. 
  Isn't this sufficient?

Thanks,
Florian