native str attributes default to null instead of empty string

[p6rt]

Migrated from rt.perl.org#126492 (status was 'open')

Searchable as RT126492$

[p6rt]

From @lizmat

[21​:38​:17] <lizmat> m​: use nqp; class A { has str $!a; method BUILD() { nqp​::chars($!a) } }; A.new # tada
[21​:38​:18] <+camelia> rakudo-moar 3cc195​: OUTPUT«(signal SEGV)»
[21​:38​:46] <lizmat> m​: use nqp; my str $foo; say $foo
[21​:38​:46] <+camelia> rakudo-moar 3cc195​: OUTPUT«␤»
[21​:39​:05] <lizmat> I always thought that native strings initialized to the empty string ?
[21​:39​:23] <lizmat> jnthn​: ^^^ ??
[21​:39​:46] <jnthn> lizmat​: In Rakudo I think we make that happen.
[21​:39​:50] <jnthn> In NQP maybe not
[21​:39​:51] <lizmat> m​: use nqp; my str $foo; say nqp​::chars($foo)
[21​:39​:51] <+camelia> rakudo-moar 3cc195​: OUTPUT«0␤»
[21​:40​:17] <lizmat> apparently it only goes wrong with native string attributes ?
[21​:40​:41] <lizmat> jnthn​: this is rakudo, so bug?
[21​:41​:39] <jnthn> lizmat​: oh, mis-read...
[21​:41​:58] <jnthn> Yeah, bug then
[21​:42​:10] <lizmat> ok, will rakudobug it

[p6rt]

From @smls

Doesn't segfault for me on...

  Rakudo version 2016.04-155-gdc7346b built on MoarVM version 2016.04
  implementing Perl 6.c.

...and instead prints this error​:

  ➜ use nqp; my str $a; say nqp​::chars($a);
  0
  ➜ use nqp; class A { has str $!a; method BUILD() { nqp​::chars($!a) } }; A.new;
  chars requires a concrete string, but got null

I'm renaming the ticket accordingly.

[p6rt]

The RT System itself - Status changed from 'new' to 'open'