"gem install mini_racer" Fails on Ubuntu 24.04

[MaZderMind]

Hi There!

I'm chasing a Problem that happens with the packaged ruby on Ubuntu 24.04. I'm not sure if it is a packaging bug in Ubuntu or a packaging issue in libv8-node or a Problem in rubygems itself – nevertheless I think it probably affects lots of people (or at least I expect it to). Bear with me to the end of the analysis.
The Problem does not arise when the same ruby version is installed with ruby-install in the same environment.

Reproducing

Reproducing is simple and works reliable in x86_64 linux and on aarch64 macos:

» docker run -it ubuntu:24.04 bash
root@98484a7e79bb:/# apt update && apt install -y ruby ruby-dev build-essential
root@98484a7e79bb:/# gem install mini_racer
…
compiling mini_racer_extension.cc
linking shared-object mini_racer_extension.so
/usr/bin/ld: cannot find /var/lib/gems/3.2.0/gems/libv8-node-21.7.2.0-x86_64-linux/vendor/v8/x86_64-linux-gnu/libv8/obj/libv8_monolith.a: No such file or directory

The file mentioned in the Makefile is
/var/lib/gems/3.2.0/gems/libv8-node-21.7.2.0-x86_64-linux/vendor/v8/x86_64-linux-gnu/libv8/obj/libv8_monolith.a
the actual file on disk is
/var/lib/gems/3.2.0/gems/libv8-node-21.7.2.0-x86_64-linux/vendor/v8/x86_64-linux/libv8/obj/libv8_monolith.a
without the -gnu suffix.

Analysis

mini_racer depends on libv8-node which in its .gem-File contains the libv8_monolith.a-File under the Path x86_64-linux/libv8/obj/libv8_monolith.a without the -gnu suffix.

During installation of mini_racer it tries to build the mini_racer_extension and dynamicly generates a Makefile for it. During that process it calls out to Libv8 to have it add its build instructions to the Makefile: https://github.com/rubyjs/mini_racer/blob/6ea0026/ext/mini_racer_extension/extconf.rb#L77

The offending line in the Makefile reads

ldflags  = /var/lib/gems/3.2.0/gems/libv8-node-21.7.2.0-x86_64-linux/vendor/v8/x86_64-linux-gnu/libv8/obj/libv8_monolith.a  -lstdc++ -L. -Wl,-Bsymbolic-functions -Wl,-z,relro -Wl,-z,now -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed

containing the incorrect x86_64-linux-gnu path (be reminded that the file would be found without the -gnu-suffix).

To generate the Makefile, Libv8::Node.configure_makefile calls out to Location.configure calling Libv8::Node::Paths.include_paths which constructs the linker-path like this: https://github.com/rubyjs/libv8-node/blob/4460470/ext/libv8-node/paths.rb#L14-L20 - relying on the return-value of def platform which is defined as

    def platform
      Gem::Platform.local.tap { |p| RUBY_PLATFORM =~ /musl/ && p.version.nil? && p.instance_eval { @version = 'musl' } }.to_s.gsub(/-darwin-?\d+/, '-darwin')
    end

And indeed print(Gem::Platform.local) returns x86_64-linux-gnu on Ubuntu 24.04 whereas it returns x86_64-linux on Ubuntu 22.04 or on Ubuntu 24.04 when the same ruby-Version is installed with ruby-install:

root@50bfef8ba8ad:/# irb
irb(main):001:0> print(Gem::Platform.local)
x86_64-linux-gnu=> nil
irb(main):002:0> 
root@50bfef8ba8ad:/# cat /etc/os-release
PRETTY_NAME="Ubuntu 24.04 LTS"

root@b9877adcebe3:/# irb
irb(main):001:0> print(Gem::Platform.local)
x86_64-linux=> nil
irb(main):002:0> 
root@b9877adcebe3:/# cat /etc/os-release
PRETTY_NAME="Ubuntu 22.04.4 LTS"

root@0a815b793f79:/ruby-install-0.9.3# /opt/rubies/ruby-3.2.3/bin/irb 
irb(main):001:0> print(Gem::Platform.local)
x86_64-linux=> nil
irb(main):002:0> 
root@0a815b793f79:/ruby-install-0.9.3# cat /etc/os-release
PRETTY_NAME="Ubuntu 24.04 LTS"

The Information in Gem::Platform.local is read from the CONFIG["arch"] entry of therbconfig.rb-File that is generated at build-time, however this entry contains the same value on Ubuntu 22.04 as on Ubuntu 24.04:

root@50bfef8ba8ad:/# grep '"arch"' /usr/lib/x86_64-linux-gnu/ruby/3.2.0/rbconfig.rb
  CONFIG["arch"] = "x86_64-linux-gnu"

root@b9877adcebe3:/# grep '"arch"' /usr/lib/x86_64-linux-gnu/ruby/3.0.0/rbconfig.rb 
  CONFIG["arch"] = "x86_64-linux-gnu"

however on the Version installed via ruby-install the Value is different:

root@0a815b793f79:/ruby-install-0.9.3# grep '"arch"' /opt/rubies/ruby-3.2.3/lib/ruby/3.2.0/x86_64-linux/rbconfig.rb
  CONFIG["arch"] = "x86_64-linux"

The change in behavior between Ubuntu 22.04 and 24.04 is therefore also triggered by change in the post-processing done in Gem::Platform.local. I think this is triggered by this Commit: 7e976d7

Looking at the changes tests I guess that this was a deliberate change to remove the "special"-Meaning of "having no suffix at all == gnu" and making it explicit. If this is the case, the root-cause is either a packaging-bug in Ubuntu, which should write an arch-Value "x86_64-linux" without -gnu-Suffix or a packaging-bug in libv8-node which should handle the -gnu suffix in Libv8::Node::Paths.platform.

I /think/ it is probably the latter because I guess the Ubuntu-Package is build against libc (gnu) while the ruby-install is statically linked and therefore not tied to libc (gnu) but at that point I'm honestly just guessing. I would love to hear from someone who could confirm my assumptions and guide me in the right direction to report the issue further.

Best regards,
Peter from Seibert Media

PS. I have searched for information on this issue all day and did not find anything exactly related. Please apologize if I missed the relevant existing discussion because I did not know what to search for.

[MaZderMind]

Just as I finished writing I checked the PR Tab on libv8-node and found rubyjs/libv8-node#36 which handles this exact issue. Therefore I will close this discussion.

I still hope that it helps people to find the right solution in the future.