Call cross_compiling block for native platform too

[larskanis]

Currently the cross_compiling block isn't called when cross compiling for the build platform.
This is due to the fact that define_native_tasks() is called first for the build platform
and later on for the cross platforms. The task "native::" is defined
only once and therefore only without the callback. The callback is therefore not called
for the cross platform that equals the build platform.

OMHO the root issue is that rake-compiler doesn't has a clear separation between
native and cross tasks. However I think calling cross_compiling for any binary gem
(native or cross) is a suitable workaround.

This fixes bug sparklemotion/nokogiri#1991 (comment)

[kou]

Sorry for late response...
Could you show how to reproduce this with Nokogiri?

[larskanis]

Build on x86_64-linux:

$ git clone https://github.com/sparklemotion/nokogiri
$ cd nokogiri
$ git checkout 33e5b426f099da152904617e4e0be3c63df1f5dd~ # commit before the above fix
$ bundle
$ rake gem:linux
$ gem inst -l pkg/nokogiri-1.11.0.rc1-x86-linux.gem 
Nokogiri is built with the packaged libraries: libxml2-2.9.10, libxslt-1.1.34, zlib-1.2.11, libiconv-1.15.
Successfully installed nokogiri-1.11.0.rc1-x86-linux

$ gem inst -l pkg/nokogiri-1.11.0.rc1-x86_64-linux.gem 
Successfully installed nokogiri-1.11.0.rc1-x86_64-linux

Note the missing message Nokogiri is built with the packaged libraries of the x86_64-linuxversion. This is because the cross_compiling hook wasn't called.

[flavorjones]

Hi, I'm still struggling with this issue in Nokogiri, see sparklemotion/nokogiri#2078 for context and help seeing the problem in the codebase.

I'd like to gently ask that this be merged, so that I can reliably build native gems for Nokogiri in the upcoming v1.11.0 release (that will coincide with Ruby 3). Thank you!

[kou]

Sorry for my lazy response again...

I could reproduce this by #171 (comment) . Thanks.

The cross_compiling hook isn't called because it's not cross compiling. rake-compiler-dock uses x86_64-linux environment. So building gem for x86_64-linux isn't cross compiling.

How about using Rake::ExtensionTask#no_native=?

diff --git a/Rakefile b/Rakefile
index 6c740a90..7b9d5f44 100644
--- a/Rakefile
+++ b/Rakefile
@@ -128,6 +128,7 @@ else
   Rake::ExtensionTask.new("nokogiri", HOE.spec) do |ext|
     ext.lib_dir = File.join(*['lib', 'nokogiri', ENV['FAT_DIR']].compact)
     ext.config_options << ENV['EXTOPTS']
+    ext.no_native = (ENV["FORCE_CROSS_COMPILING"] == "true")
     ext.cross_compile  = true
     ext.cross_platform = CROSS_RUBIES.map(&:platform).uniq
     ext.cross_config_options << "--enable-cross-build"
diff --git a/tasks/cross-ruby.rb b/tasks/cross-ruby.rb
index b77d7b43..78cc6fd8 100644
--- a/tasks/cross-ruby.rb
+++ b/tasks/cross-ruby.rb
@@ -166,7 +166,7 @@ namespace "gem" do
       RakeCompilerDock.sh <<-EOT, platform: plat
         gem install bundler --no-document &&
         bundle &&
-        rake native:#{plat} pkg/#{HOE.spec.full_name}-#{plat}.gem MAKE='nice make -j`nproc`' RUBY_CC_VERSION=#{ENV["RUBY_CC_VERSION"]}
+        rake native:#{plat} pkg/#{HOE.spec.full_name}-#{plat}.gem MAKE='nice make -j`nproc`' RUBY_CC_VERSION=#{ENV["RUBY_CC_VERSION"]} FORCE_CROSS_COMPILING=true
       EOT
     end
   end

[flavorjones]

@kou Thank you for responding!

I tried your suggestion, and ✨ it totally worked ✨. It also addressed sparklemotion/nokogiri#2076 which resulted in a "native" nokogiri.so being generated and packaged in addition to the "cross-compiled" libraries.

I'm going to play with this a bit more to make sure it's totally working the way I expect, but I think you've solved multiple problems for us. Thank you! 💕

[kou]

Thanks for confirming it.
Can we close this?

[flavorjones]

@kou If you'd like to close, OK. I'm pretty confident I can get sparklemotion/nokogiri#2125 to pass CI.

Thank you again!

[kou]

OK.
Closing.

[larskanis]

@kou Thank you for the hint to use no_native=true! I added this to the rake-compiler-dock readme in rake-compiler/rake-compiler-dock@8a0c7ce .

What do you think about adding this directly to rake-compiler? The environment variable RCD_HOST_RUBY_PLATFORM is always defined by rake-compiler-dock.

[kou]

OK. You can use RAKE_EXTENSION_TASK_NO_NATIVE=true with 15f630a.

[larskanis]

Looks good - thanks!