psst!

These are not official practices. They may not be available in the future.

• (approach 1) Specify a file in the build configuration file that contains an additional presym.

  Interrupt the task with the file task method and intervene with the Binding#local_variable_get method to the local variable ppps.
  The ppps variable is passed to presym.scan.
  

  mruby/tasks/presym.rake

  Line 36 in 4845575

  presyms = presym.scan(ppps)

  MRuby::Build.new do
    ...
  
    mypresyms = "path/to/extra-presyms.txt"
    presym_path = File.join(self.build_dir, "presym")
    file presym_path => mypresyms do |t|
      e = t.actions[1].binding
      e.local_variable_get(:ppps) << mypresyms
    end
  end

  As for the contents of the extra-presyms.txt file, symbols must be enclosed in <@! " and " !@>.

  <@! "extra_symbol1" !@>
  <@! "extra_symbol2" !@>
  <@! "$global_variable" !@>
  <@! "\x01\x02\x03" !@>
  

• (approach 2) Interrupt the `presym.scan` method.

  In the block of MRuby::Build.new, presym is still undefined.
  Interrupt MRuby::Build#define_rules to interrupt the scan method of MRuby::Build#presym.

  MRuby::Build.new do
    ...
  
    def self.define_rules
      super
  
      class << self.presym
        def scan(*args)
          presyms = super(*args)
          presyms << "extra_symbol1"
          presyms << "extra_symbol2"
          presyms << "$global_variable"
          presyms << "\x01\x02\x03"
          presyms.uniq!
          presyms.sort_by! { |e| [e.bytesize, e] }
          presyms
        end
      end
    end
  end

The reason is that the number of symbols used in the application and the symbols corresponding to global variables is small, so we thought the impact would be small. Another reason is that presym scan and allocation are done during the libmruby build, so it was difficult to apply to symbols in the app.