Use append_cflags instead of modifying CFLAGS directly

[skatkov]

Linux system with latest GCC 15 can't compile this gem. See more #136

Types of Changes

Use append_cflags instead of modifying CFLAGS directly

According to this thread
https://inbox.vuxu.org/ruby-core/redmine.issue-21290.20250428190637.58020@ruby-lang.org/T/

ed25519 gem had a similar issue, and it was resolved by migrating to append_cflags.
RubyCrypto/ed25519@c1ee0e0

Let's move this gem to append_cflags as well. This approach is recommended over modifying CFLAGS since it ensures compatibility across different build environments by checking whether the flag is acceptable, and should not affect most systems.

In the meantime, it appears that Nobu has merged a wider fix to ruby itself. But this improvement will not hurt in the long term.

Testing

Building this branch with bake build works on my machine. At the same time, main branch is failing.

Contribution

• I added tests for my changes.
• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.

[skatkov]

@ioquatix would appreciate it if you can take a look here. I got blocked with one of my client projects due to this.

[ioquatix]

I will sort it out today.

[jakob-lilliemarck]

I am running in to this exact issue:

/home/jakob/.rvm/rubies/ruby-3.2.7/include/ruby-3.2.0/ruby/internal/scan_args.h:390:30: note: ‘bool’ is defined in header ‘<stdbool.h>’; this is probably fixable by adding ‘#include <stdbool.h>’
/home/jakob/.rvm/rubies/ruby-3.2.7/include/ruby-3.2.0/ruby/internal/scan_args.h:390:43: error: unknown type name ‘bool’

trying to bundle install a Ruby project using:

• Fedora Linux 42 (KDE Plasma)
• Ruby 3.2.3
• GCC 15.1.1-2

The issue is with io-event:

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

    current directory: /home/jakob/.rvm/gems/ruby-3.2.7/gems/io-event-1.1.7/ext
/home/jakob/.rvm/rubies/ruby-3.2.7/bin/ruby extconf.rb
checking for rb_ext_ractor_safe()... *** 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}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=/home/jakob/.rvm/rubies/ruby-3.2.7/bin/$(RUBY_BASE_NAME)
/home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:490:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.

        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:583:in `try_link0'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:601:in `try_link'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:812:in `try_func'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:1116:in `block in have_func'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:989:in `block in checking_for'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:354:in `block (2 levels) in postpone'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:324:in `open'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:354:in `block in postpone'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:324:in `open'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:350:in `postpone'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:988:in `checking_for'
        from /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/mkmf.rb:1115:in `have_func'
        from extconf.rb:42:in `<main>'

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

  /home/jakob/.rvm/gems/ruby-3.2.7/extensions/x86_64-linux/3.2.0/io-event-1.1.7/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /home/jakob/.rvm/gems/ruby-3.2.7/gems/io-event-1.1.7 for inspection.
Results logged to /home/jakob/.rvm/gems/ruby-3.2.7/extensions/x86_64-linux/3.2.0/io-event-1.1.7/gem_make.out

  /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/rubygems/ext/builder.rb:119:in `run'
  /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/rubygems/ext/ext_conf_builder.rb:28:in `build'
  /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/rubygems/ext/builder.rb:187:in `build_extension'
  /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/rubygems/ext/builder.rb:221:in `block in build_extensions'
  /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/rubygems/ext/builder.rb:218:in `each'
  /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/rubygems/ext/builder.rb:218:in `build_extensions'
  /home/jakob/.rvm/rubies/ruby-3.2.7/lib/ruby/3.2.0/rubygems/installer.rb:846:in `build_extensions'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/rubygems_gem_installer.rb:72:in `build_extensions'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/rubygems_gem_installer.rb:28:in `install'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/source/rubygems.rb:200:in `install'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/installer/gem_installer.rb:54:in `install'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/installer/gem_installer.rb:16:in `install_from_spec'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/installer/parallel_installer.rb:167:in `do_install'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/installer/parallel_installer.rb:158:in `block in worker_pool'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/worker.rb:62:in `apply_func'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/worker.rb:57:in `block in process_queue'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/worker.rb:54:in `loop'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/worker.rb:54:in `process_queue'
  /home/jakob/.rvm/gems/ruby-3.2.7/gems/bundler-2.4.7/lib/bundler/worker.rb:90:in `block (2 levels) in create_threads'

An error occurred while installing io-event (1.1.7), and Bundler cannot continue.

In Gemfile:
  async-websocket was resolved to 0.8.0, which depends on
    async-io was resolved to 1.34.3, which depends on
      async was resolved to 2.5.0, which depends on
        io-event

Feels like I have installed every conceivable development tools package there is 🤷

[skatkov]

Try updating a gem, fix already landed with a release.