brew/Library/Homebrew/compilers.rb

class Compilers < Array
  def include? cc
    cc = cc.name if cc.is_a? Compiler
    self.any? { |c| c.name == cc }
  end
end


class CompilerFailures < Array
  def include? cc
    cc = Compiler.new(cc) unless cc.is_a? Compiler
    self.any? { |failure| failure.compiler == cc.name }
  end

  def <<(failure)
    super(failure) unless self.include? failure.compiler
  end
end


class Compiler
  attr_reader :name, :build

  def initialize name
    @name = name
    @build = case name
    when :clang then MacOS.clang_build_version.to_i
    when :llvm then MacOS.llvm_build_version.to_i
    when :gcc then MacOS.gcc_42_build_version.to_i
    end
  end

  def ==(other)
    @name.to_sym == other.to_sym
  end
end


class CompilerFailure
  attr_reader :compiler

  def initialize compiler, &block
    @compiler = compiler
    instance_eval(&block) if block_given?
  end

  def build val=nil
    val.nil? ? @build.to_i : @build = val.to_i
  end

  def cause val=nil
    val.nil? ? @cause : @cause = val
  end
end


# CompilerSelector is used to process a formula's CompilerFailures.
# If no viable compilers are available, ENV.compiler is left as-is.
class CompilerSelector
  NAMES = { :clang => "Clang", :gcc => "GCC", :llvm => "LLVM" }

  def initialize f
    @f = f
    @old_compiler = ENV.compiler
    @compilers = Compilers.new
    @compilers << Compiler.new(:clang) if MacOS.clang_build_version
    @compilers << Compiler.new(:llvm) if MacOS.llvm_build_version
    @compilers << Compiler.new(:gcc) if MacOS.gcc_42_build_version
  end

  def select_compiler
    # @compilers is our list of available compilers. If @f declares a
    # failure with compiler foo, then we remove foo from the list if
    # the failing build is >= the currently installed version of foo.
    @compilers.reject! do |cc|
      failure = @f.fails_with? cc
      next unless failure
      failure.build >= cc.build
    end

    return if @compilers.empty? or @compilers.include? ENV.compiler

    ENV.send case ENV.compiler
    when :clang
      if @compilers.include? :llvm then :llvm
      elsif @compilers.include? :gcc then :gcc
      else ENV.compiler
      end
    when :llvm
      if @compilers.include? :clang and MacOS.clang_build_version >= 211 then :clang
      elsif @compilers.include? :gcc then :gcc
      elsif @compilers.include? :clang then :clang
      else ENV.compiler
      end
    when :gcc
      if @compilers.include? :clang and MacOS.clang_build_version >= 211 then :clang
      elsif @compilers.include? :llvm then :llvm
      elsif @compilers.include? :clang then :clang
      else ENV.compiler
      end
    end
  end

  def advise
    failure = @f.fails_with? @old_compiler
    return unless failure

    # If we're still using the original ENV.compiler, then the formula did not
    # declare a specific failing build, so we continue and print some advice.
    # Otherwise, tell the user that we're switching compilers.
    if @old_compiler == ENV.compiler
      cc = Compiler.new(ENV.compiler)
      subject = "#{@f.name}-#{@f.version}: builds with #{NAMES[cc.name]}-#{cc.build}-#{MACOS_VERSION}"
      warning = "Using #{NAMES[cc.name]}, but this formula is reported to fail with #{NAMES[cc.name]}."
      warning += "\n\n#{failure.cause.strip}\n" unless failure.cause.nil?
      warning += <<-EOS.undent

        We are continuing anyway so if the build succeeds, please open a ticket with
        the subject

          #{subject}

        so that we can update the formula accordingly. Thanks!
        EOS

      viable = @compilers.reject { |cc| @f.fails_with? cc }
      unless viable.empty?
        warning += "\nIf it fails you can use "
        options = viable.map { |cc| "--use-#{cc.name}" }
        warning += "#{options*' or '} to try a different compiler."
      end

      opoo warning
    end
  end
end