Module is broken with Readline 7.0

[samcv]

https://lists.gnu.org/archive/html/info-gnu/2016-09/msg00009.html
Readline 7.0 has been out almost a month, and it will be out of Arch's testing repository in a day or two.
Here is the error:

Cannot locate native library 'libreadline.so.6': libreadline.so.6: cannot open shared object file: No such file or directory
  in method setup at /home/user/rakudo/install/share/perl6/sources/24DD121B5B4774C04A7084827BFAD92199756E03 (NativeCall) line 310
  in method CALL-ME at /home/user/rakudo/install/share/perl6/sources/24DD121B5B4774C04A7084827BFAD92199756E03 (NativeCall) line 322
  in method make-bare-keymap at /home/samantha/panda/.panda-work/1479105484_2/lib/Readline.pm (Readline) line 1040
  in sub  at t/02-base.t line 162
  in sub subtest at /home/user/rakudo/install/share/perl6/sources/C712FE6969F786C9380D643DF17E85D06868219E (Test) line 364
  in sub  at t/02-base.t line 161
  in sub subtest at /home/user/rakudo/install/share/perl6/sources/C712FE6969F786C9380D643DF17E85D06868219E (Test) line 364
  in block <unit> at t/02-base.t line 155

[samcv]

For anybody landing here:
Change this line: https://github.com/drforr/perl6-readline/blob/master/lib/Readline.pm#L657

And remove the version. So the line becomes: my constant LIB = ( 'readline' );

Disclaimer: could have some differences because of differences between Readline 6 and 7, but if you only have Readline 7 available this should work, and not error out.

[cono]

Well, actually this is not proper way to handle this.
Because libreadline.so is not proper SONAME and dlopen by opening libreadline.so file fails on some systems:

# Failed test 'initialize'
# at t/02-base.t line 11
# Cannot locate native library 'libreadline.so': /usr/lib64/libreadline.so: invalid ELF header
    not ok 1 - macro-dumper lives

Due to the file libreadline.so is not a shared object, its an LD script:

% cat /usr/lib64/libreadline.so 
/* GNU ld script
   Since Gentoo has critical dynamic libraries in /lib, and the static versions
   in /usr/lib, we need to have a "fake" dynamic lib in /usr/lib, otherwise we
   run into linking problems.  This "fake" dynamic lib is a linker script that
   redirects the linker to the real lib.  And yes, this works in the cross-
   compiling scenario as the sysroot-ed linker will prepend the real path.

   See bug https://bugs.gentoo.org/4411 for more info.
 */
OUTPUT_FORMAT ( elf64-x86-64 )
GROUP ( /lib64/libreadline.so.6 )

Proper way would be to make a factory which provides unified interface to different libreadline version and handle different version differently. And use proper SONAME:

% objdump -x /lib64/libreadline.so.6 | grep SONAME
  SONAME               libreadline.so.6

Detailed explanation here:
https://bugs.gentoo.org/show_bug.cgi?id=290974

[nxadm]

@samcv

In my case (Ubuntu 18.04 amd64), the fix was the reverse as there is no unversioned .so in Ubuntu 18.04:

$ ls -la /lib/x86_64-linux-gnu/libreadline*
lrwxrwxrwx 1 root root     18 feb  7  2016 /lib/x86_64-linux-gnu/libreadline.so.5 -> libreadline.so.5.2
-rw-r--r-- 1 root root 249144 feb  7  2016 /lib/x86_64-linux-gnu/libreadline.so.5.2
lrwxrwxrwx 1 root root     18 mei 15  2017 /lib/x86_64-linux-gnu/libreadline.so.7 -> libreadline.so.7.0
-rw-r--r-- 1 root root 294632 mei 15  2017 /lib/x86_64-linux-gnu/libreadline.so.7.0

To fix the Readline module, in https://github.com/drforr/perl6-readline/blob/master/lib/Readline.pm#L657 change:
from my constant LIB = ( 'readline' );
to my constant LIB = ( 'readline', v7 );

[drforr]

Long time to leave this open, I know. Closing because the Perl library now looks in /lib/x86_64-linux-gnu for installed library versions and picks the highest version it can find. I'll eventually add a way to choose the exact library via environment or something.