Ruby LoadError with gmp

Question

$ gem install gmp
Building native extensions. This could take a while...
Successfully installed gmp-0.7.43
Parsing documentation for gmp-0.7.43
Done installing documentation for gmp after 0 seconds
1 gem installed


$ cat gmp-test.rb
require 'gmp'

$ /opt/src/ruby-3.2.0/bin/ruby gmp-test.rb
<internal:/opt/src/ruby-3.2.0/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:85:in `require': cannot load such file -- /home/dunham/.local/share/gem/ruby/3.2.0/gems/gmp-0.7.43/lib/../ext/gmp (LoadError)
    from <internal:/opt/src/ruby-3.2.0/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
    from /home/dunham/.local/share/gem/ruby/3.2.0/gems/gmp-0.7.43/lib/gmp.rb:9:in `<top (required)>'
    from <internal:/opt/src/ruby-3.2.0/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:159:in `require'
    from <internal:/opt/src/ruby-3.2.0/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:159:in `rescue in require'
    from <internal:/opt/src/ruby-3.2.0/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:149:in `require'
    from gmp-test.rb:1:in `<main>'
<internal:/opt/src/ruby-3.2.0/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:85:in `require': cannot load such file -- gmp (LoadError)
    from <internal:/opt/src/ruby-3.2.0/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
    from gmp-test.rb:1:in `<main>'

Answer 1

Library seems to be dead. It's expecting gmp.so to be in ext directory but it ends up in lib directory, it's probably new rubygems doing things differently.

>> require "gmp"
<internal:/home/alex/.rbenv/versions/3.2.0/lib/ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:85:in 'require': 
cannot load such file -- /home/alex/.rbenv/versions/3.2.0/lib/ruby/gems/3.2.0/gems/gmp-0.7.43/lib/../ext/gmp (LoadError)

$ ls $(dirname $(gem which gmp))
gmp.rb  gmp.so
#  move ^ that to ../ext/

$ mv $(dirname $(gem which gmp))/gmp.so $(dirname $(gem which gmp))/../ext/

>> require "gmp"
=> true
>> GMP::Z(0)
=> 0

---

Update

From the linked logs looks like you're still not loading gmp.so which is where all the classes are defined. You can copy gmp.so into your app:

# copy `gmp.rb`
$ cp $(gem which gmp) .
# copy `gmp.so`
$ cp $(dirname $(gem which gmp))/gmp.so .
# or if you moved it to ext
$ cp $(dirname $(gem which gmp))/../ext/gmp.so .

$ touch app.rb
$ ls
app.rb  gmp.rb  gmp.so

gmp.rb defines GMP.sprintf method, if this is not a required method and you don't use it, you can remove this file.

# gmp.rb

# require 'rbconfig'
#
# ENV['PATH'] = [File.expand_path(
#   File.join(File.dirname(__FILE__), "..", "ext")
# ), ENV['PATH']].compact.join(';') if RbConfig::CONFIG['host_os'] =~ /(mswin|mingw|mingw32)/i
#
# require File.dirname(__FILE__) + '/../ext/gmp'

# unless RUBY_VERSION =~ /^1.8/
  module GMP
    def self.sprintf(format, *args)
      first_pct = format.index '%'
      result = format[0...first_pct]
      #format.gsub(/(?<!%)%[0#+ ']*[0-9]*.?[0-9]*[a-zA-Z][^%]*/) do |fragment|
      format.gsub(Regexp.new('(?<!%)%[0#+ \']*[0-9]*.?[0-9]*[a-zA-Z][^%]*')) do |fragment|
        arg = args.shift
        if fragment =~ /%[0#+ ']*[0-9]*.?[0-9]*[ZQF]/
          result << sprintf2(fragment, arg)
        elsif fragment =~ /%[0#+ ']*[0-9]*.?[0-9]*[PR]/ && GMP.const_defined?(:MPFR_VERSION)
          result << GMP::F.sprintf2(fragment, arg)
        else
          result << (fragment % arg)
        end
      end
      result
    end
  end
# end

# app.rb

require_relative "gmp.so"
p GMP::Z
p GMP::Z(0)
p GMP::Q
p GMP::F

require_relative "gmp.rb"
p GMP.sprintf "%Zd", GMP.Z(0)

$ ruby --yjit -v
ruby 3.2.0 (2022-12-25 revision a528908271) +YJIT [x86_64-linux]
$ ruby --yjit app.rb
GMP::Z
0
GMP::Q
GMP::F
"0"