Dont use rubygems on extconf

[arthurnn]

extconf.rb fail to run when disabling rubygems:
RUBYOPT='--disable-gems' rake

Instead of requiring rubygems here, we could just use rbconfig instead.

See error that happens without this PR:

[arthurnn@snowball test_bundler]$ RUBYOPT='--disable-gems' bundle
Fetching gem metadata from https://rubygems.org/..
Fetching version metadata from https://rubygems.org/.
Resolving dependencies...
Using bundler 1.11.2
Installing ruby-prof 0.15.9 with native extensions

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /Users/arthurnn/.gem/ruby/2.3.0/gems/ruby-prof-0.15.9/ext/ruby_prof
/Users/arthurnn/.rubies/ruby-2.3.0/bin/ruby -r ./siteconf20160502-97773-1kxo9fy.rb extconf.rb
checking for rb_gc_stat()... yes
checking for rb_gc_count()... yes
checking for rb_os_allocated_objects()... no
checking for rb_gc_allocated_size()... no
checking for rb_gc_collections()... no
checking for rb_gc_time()... no
checking for rb_gc_total_time()... no
checking for rb_gc_total_mallocs()... no
checking for rb_gc_total_malloced_bytes()... no
checking for rb_heap_total_mem()... no
checking for rb_gc_heap_info()... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
    --with-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/Users/arthurnn/.rubies/ruby-2.3.0/bin/$(RUBY_BASE_NAME)
extconf.rb:41:in `<main>': uninitialized constant Gem (NameError)

To see why this extension failed to compile, please check the mkmf.log which can be found here:

  /Users/arthurnn/.gem/ruby/2.3.0/extensions/x86_64-darwin-15/2.3.0-static/ruby-prof-0.15.9/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /Users/arthurnn/.gem/ruby/2.3.0/gems/ruby-prof-0.15.9 for inspection.
Results logged to /Users/arthurnn/.gem/ruby/2.3.0/extensions/x86_64-darwin-15/2.3.0-static/ruby-prof-0.15.9/gem_make.out
An error occurred while installing ruby-prof (0.15.9), and Bundler cannot continue.
Make sure that `gem install ruby-prof -v '0.15.9'` succeeds before bundling.

[skaes]

Looks OK to me but I'm curious: why would you want to disable gems?

[arthurnn]

@skaes We(GitHub) have a few ruby scripts that run with less environment loaded as possible for speed. I dont know how faster they are TBH, but I found this while running bundle install, which for us uses disable-gems as ruby option.

[skaes]

@arthurnn got it. thx for the info.

[glensc]

@skaes could you please make new release, ruby-prof-0.15.9 is added in gitlab-8.11 and i fail to build it because your extconf.rb uses Gem symbol without prior require "rubygems".

*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
        --with-opt-dir
        --without-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib64
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=/usr/bin/ruby
extconf.rb:41:in `<main>': uninitialized constant Gem (NameError)

extconf failed, exit code 1

Gem files will remain installed in /home/users/glen/rpm/BUILD/x86_64-linux/gitlabhq-8.11.0/vendor/bundle/ruby/gems/ruby-prof-0.
15.9 for inspection.
Results logged to /home/users/glen/rpm/BUILD/x86_64-linux/gitlabhq-8.11.0/vendor/bundle/ruby/extensions/x86_64-linux/ruby-prof-
0.15.9/gem_make.out

[skaes]

@glensc I'm confused: 0.15.9 does not include the patch discussed here. It's only on master branch.

BTW, requiring rubygems has been obsolete now for a long time. Which ruby version are you using?

[skaes]

@glensc Gem is defined in my ruby:

$ ruby -v
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin15]
$ ruby -e 'puts(defined? Gem)'
constant

[glensc]

@skaes as outlined in #191 (comment)
i also have ruby which was built with --disable-gems
i think ruby version is irrelevant, what is relevant whether ruby was built with preloading rubygems library

and 0.15.9 is broken for me, as patch from this PR is needed to fix build with my ruby.

any trustworthy link about requiring rubygems has been obsolete now for a long time?

i'd say as long ruby has --disable-gems configure option code that uses Gem symbol should ensure rubygems module is loaded.

anyway, could you just release new version (and i'll ping gitlab dudes to bump their deps) as this is only gem that fails to build on my system.

# ruby -v
ruby 2.0.0p648 (2015-12-16) [x86_64-linux]

# ruby -e 'puts(defined? Gem)'

[skaes]

I did not know about --disable-gems being a compile time option for ruby and with obsolete I meant that since 1.9.x rubygems is required by default in a "normal" ruby installation.

Anyway, I'm going to release an updated gem to fix your problem.

[skaes]

Released as 0.16.0

[skaes]

Please use 0.16.1. 0.16.0 won't work for ruby 2.1.10.

[glensc]

thanks!

[glensc]

@skaes could you also push out git tags so the releases be visible?
https://github.com/ruby-prof/ruby-prof/releases

[glensc]

filed https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6026

[skaes]

@glensc please use 0.16.2.

[glensc]

right. thanks