drop rb_safe_level() from ruby-curses to fix irqtop from missing symbols and deprecation warnings

[Ferdinand Postema]

[Impact]

rb_safe_level() had been marked for deprecation for some time, and was finally removed in Ruby 3.0.

ruby-curses uses rb_safe_level(), and it causes issues with its rdepends, most notably irqtop.

irqtop is unusuable on Jammy, with it failing to start due to not finding the rb_safe_level symbol.

$ sudo irqtop
<internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require': /usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/3.0.0/curses.so: undefined symbol: rb_safe_level - /usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/3.0.0/curses.so (LoadError)
 from <internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require'
 from /usr/lib/ruby/vendor_ruby/curses.rb:18:in `rescue in <top (required)>'
 from /usr/lib/ruby/vendor_ruby/curses.rb:14:in `<top (required)>'
 from <internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require'
 from <internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require'
 from /usr/bin/irqtop:9:in `<main>'

On Focal, irqtop fills the screen with deprecation warnings making the tool unusable.

/usr/bin/irqtop:545: warning: rb_safe_level will be removed in Ruby 3.0

[Testcase]

$ sudo apt install irqtop
$ sudo irqtop

On Jammy:
Check to see if the tool launches, and you no longer get the "undefined symbol: rb_safe_level - /usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/3.0.0/curses.so (LoadError)" error.

on Focal:
Launch the tool, press enter several times to refresh the results. There should be no mention of "/usr/bin/irqtop:545: warning: rb_safe_level will be removed in Ruby 3.0", and the tool should be readable.

Test packages are available in the following ppa:

https://launchpad.net/~mruffell/+archive/ubuntu/sf385554-test

If you install the test packages, irqtop will function normally.

[Where Problems Could Occur]

We are removing a long deprecated string safety check, which I assure you, does not change the security of the tools using the ruby-curses library, due to most levels being disabled already in ruby itself.

As for the effect on the programs that depend on ruby-curses, ruby-curses only has 2 redepends, one of which is irqtop:

$ apt rdepends ruby-curses
ruby-curses
Reverse Depends:
  Depends: irqtop
  Depends: ruby-blade

If a regression were to occur, it would only impact irqtop and ruby-blade users. Users could downgrade ruby-curses while a fix is developed.

[Other Info]

This was fixed in the below commit, in version 1.3.2:

commit a9b9db9b5d5a4b52e3d0e0eaf0fbb2be839a3c29
From: Eric Wong <email address hidden>
Date: Sat, 30 Nov 2019 01:45:21 +0000
Subject: drop rb_safe_level check
Link: https://github.com/ruby/curses/commit/a9b9db9b5d5a4b52e3d0e0eaf0fbb2be839a3c29

Both Focal and Jammy required a backport. Only window and mouse events are implemented in 1.2.4, so I removed the hunks that targeted events that were implemented later.

[Axel Beckert (xtaran)]

This is an issue in ruby-curses, not irqtop. See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=958973

Interestingly this no more happens on Debian Unstable/Testing. This seems to have fixed upstream a few months ago:

commit df3f52a6331f1a47af9933b77311a8650727d8d1
  Author: nagachika <email address hidden>
  Date: 2020-09-29 22:43:25 +0900

    merge revision(s) 996af2ce086249e904b2ce95ab2fcd1de7d757be: [Backport #16345] [Backport #17000]

            Disable deprecation warning by the default [Feature #16345]

            And `-w` option turns it on.

That commit likely made it into ruby 2.7.2, which hit Debian Unstable in mid-October 2020.

Nevertheless this obviously needs to be fixed in ruby-curses.

[Axel Beckert (xtaran)]

Note: The cited commit and "fix" was in the package ruby, but the problem in ruby-curses still exists as ruby only silenced the deprecation warnings by default.

[Erik Meitner (eamuwmath)]

Problem does not seem to be solved as now irqtop fails completely.

root@hongkong:~# irqtop
<internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require': /usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/3.0.0/curses.so: undefined symbol: rb_safe_level - /usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/3.0.0/curses.so (LoadError)
 from <internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require'
 from /usr/lib/ruby/vendor_ruby/curses.rb:18:in `rescue in <top (required)>'
 from /usr/lib/ruby/vendor_ruby/curses.rb:14:in `<top (required)>'
 from <internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require'
 from <internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require'
 from /usr/bin/irqtop:9:in `<main>'
<internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require': cannot load such file -- 3.0/curses.so (LoadError)
 from <internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require'
 from /usr/lib/ruby/vendor_ruby/curses.rb:16:in `<top (required)>'
 from <internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require'
 from <internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in `require'
 from /usr/bin/irqtop:9:in `<main>'

root@hongkong:~# dpkg -l irqtop ruby-curses
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-=============-============-=============================================
ii irqtop 2.6-2ubuntu1 all Observe IRQ and SoftIRQ in a top-like fashion
ii ruby-curses 1.2.4-1build3 amd64 curses binding for Ruby

root@hongkong:~# cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=22.04
DISTRIB_CODENAME=jammy
DISTRIB_DESCRIPTION="Ubuntu 22.04.1 LTS"

[Farshid Tavakolizadeh (farshidtz)]

This is reportedly fixed on the newer versions of ruby-curses. Here is the bug report for Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=958973

Ubuntu Jammy (22.04) is still on ruby-curses 1.2.4 which is makes irqtop nonfunctional. Newer versions of Ubuntu are not affected.

[Matthew Ruffell (mruffell)]

Attached is a debdiff for jammy which solves this issue.

[Matthew Ruffell (mruffell)]

Attached is a debdiff which solves this issue for focal.