Add todo-test for GH 13307 (hash elem ref in @_ disappears)

[zb226]

This PR adds a todo-test for #13307 where a changed behavior involving @_ from perl 5.19.4 on was noted. Current blead perl still shows the same behavior.

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• This set of changes does not require a perldelta entry.

[jkeenan]

Our Continuous Integration system has reported one failing test in your pull request. We need you to add your name (preferably something more than a github ID) and email address to AUTHORS. Please run this program from the top of your git checkout:

perl Porting/updateAUTHORS.pl 

When you're done make sure you call:

$ git add AUTHORS
$ git commit
$ make test_porting && make test_harness

... and then re-push your branch. Thanks.

[tonycoz]

A build with -Accflags=-DPERL_RC_STACK returns oooo for every line, which seems like the most reasonable result, even though that differs from what 5.18.1 produced.

blead default:

tony@venus:.../git/perl6$ ./perl -Ilib -V:ccflags
ccflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2';
tony@venus:.../git/perl6$ ./perl ../13307.pl 
undef
oooo
undef
oooo

blead with -Accflags=-DPERL_RC_STACK:

tony@venus:.../git/perl6$ ./perl -Ilib -V:ccflags
ccflags='-DPERL_RC_STACK -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2';
tony@venus:.../git/perl6$ ./perl ../13307.pl 
oooo
oooo
oooo
oooo

[zb226]

Hi, does that mean this issue will be handled elsewhere or should the test be added still?

[tonycoz]

After some thought, please make it check for the output I suggested and make the $::TODO conditional on "$Config{cc} $Config{ccflags} $Config{optimize}" !~ /-DPERL_RC_STACK\b/ - so it's a TODO test when -DPERL_RC_STACK is not found in those config variables.

[khwilliamson]

And that means we want this test to still be added; and thank you for contributing

[tonycoz]

I was thinking more:

my $is_rc_stack = "$Config{cc} $Config{ccflags} $Config{optimize}" =~ /-DPERL_RC_STACK\b/;
local $::TODO = $is_rc_stack ? undef : "GH 13307";

so we don't skip the test, but run the test non-TODO for PERL_RC_STACK and TODO for non-PERL_RC_STACK.

Also:

#   Failed test 'Is authors_file 'AUTHORS' up to date?'
#   at Porting/updateAUTHORS.pl line 130.
#   File 'AUTHORS' changes:
#     would add: zb226                          <[email protected]>
# 
# Files need updating! You probably just need to run
# 
#    Porting/updateAUTHORS.pl
# 
# and commit the results.
# Looks like you failed 1 test of 5.
porting/authors.t ......... 
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/5 subtests 

[zb226]

Is this looking OK?