fully parallelize the CFile builder

build_tests/cfile/Rsconsfile

@@ -0,0 +1,4 @@
+Rscons::Environment.new do |env|
+  env.CFile("lexer.c", "lexer.l")
+  env.CFile("parser.c", "parser.y")
+end

build_tests/cfile/error_unknown_extension.rb

@@ -0,0 +1,3 @@
+Rscons::Environment.new do |env|
+  env.CFile("file.c", "foo.bar")
+end

build_tests/cfile/lexer.l

@@ -0,0 +1,4 @@
+%{
+%}
+
+%%

build_tests/cfile/parser.y

@@ -0,0 +1,9 @@
+%{
+%}
+
+%token ONE
+
+%%
+
+one: ONE
+   ;

lib/rscons/builders/cfile.rb

@@ -7,6 +7,7 @@ module Rscons
     #   env.CFile("parser.tab.cc", "parser.yy")
     #   env.CFile("lex.yy.cc", "parser.ll")
     class CFile < Builder
+
       # Return default construction variables for the builder.
       #
       # @param env [Environment] The Environment using the builder.
@@ -48,8 +49,20 @@ module Rscons
             raise "Unknown source file #{sources.first.inspect} for CFile builder"
           end
         command = env.build_command("${#{cmd}_CMD}", vars)
-        standard_build("#{cmd} #{target}", target, command, sources, env, cache)
+        standard_threaded_build("#{cmd} #{target}", target, command, sources, env, cache)
       end
+
+      # Finalize a build.
+      #
+      # @param options [Hash]
+      #   Finalize options.
+      #
+      # @return [String, nil]
+      #   The target name on success or nil on failure.
+      def finalize(options)
+        standard_finalize(options)
+      end
+
     end
   end
 end

spec/build_tests_spec.rb

@@ -682,6 +682,30 @@ EOF
     end
   end
 
+  context "CFile builder" do
+    it "builds a .c file using flex and bison" do
+      test_dir("cfile")
+
+      result = run_test
+      expect(result.stderr).to eq ""
+      expect(Set[*lines(result.stdout)]).to eq Set[
+        "LEX lexer.c",
+        "YACC parser.c",
+      ]
+
+      result = run_test
+      expect(result.stderr).to eq ""
+      expect(result.stdout).to eq ""
+    end
+
+    it "raises an error when an unknown source file is specified" do
+      test_dir("cfile")
+      result = run_test(rsconsfile: "error_unknown_extension.rb")
+      expect(result.stderr).to match /Unknown source file .foo.bar. for CFile builder/
+      expect(result.status).to_not eq 0
+    end
+  end
+
   context "Directory builder" do
     it "creates the requested directory" do
       test_dir("simple")

spec/rscons/builders/cfile_spec.rb

@@ -1,28 +0,0 @@
-module Rscons
-  module Builders
-    describe CFile do
-      let(:env) {Environment.new}
-      subject {CFile.new}
-
-      it "invokes bison to create a .c file from a .y file" do
-        expect(subject).to receive(:standard_build).with("YACC parser.c", "parser.c", ["bison", "-d", "-o", "parser.c", "parser.y"], ["parser.y"], env, :cache)
-        subject.run("parser.c", ["parser.y"], :cache, env, {})
-      end
-
-      it "invokes a custom lexer to create a .cc file from a .ll file" do
-        env["LEX"] = "custom_lex"
-        expect(subject).to receive(:standard_build).with("LEX lexer.cc", "lexer.cc", ["custom_lex", "-o", "lexer.cc", "parser.ll"], ["parser.ll"], env, :cache)
-        subject.run("lexer.cc", ["parser.ll"], :cache, env, {})
-      end
-
-      it "supports overriding construction variables" do
-        expect(subject).to receive(:standard_build).with("LEX lexer.c", "lexer.c", ["hi", "parser.l"], ["parser.l"], env, :cache)
-        subject.run("lexer.c", ["parser.l"], :cache, env, "LEX_CMD" => ["hi", "${_SOURCES}"])
-      end
-
-      it "raises an error when an unknown source file is specified" do
-        expect {subject.run("file.c", ["foo.bar"], :cache, env, {})}.to raise_error /Unknown source file .foo.bar. for CFile builder/
-      end
-    end
-  end
-end