add CFile builder to create C/C++ sources from lex/yacc input files

lib/rscons.rb

@@ -5,6 +5,7 @@ require_relative "rscons/varset"
 require_relative "rscons/version"
 
 # default builders
+require_relative "rscons/builders/cfile"
 require_relative "rscons/builders/library"
 require_relative "rscons/builders/object"
 require_relative "rscons/builders/program"
@@ -12,6 +13,7 @@ require_relative "rscons/builders/program"
 # Namespace module for rscons classes
 module Rscons
   DEFAULT_BUILDERS = [
+    :CFile,
     :Library,
     :Object,
     :Program,

lib/rscons/builders/cfile.rb

@@ -0,0 +1,40 @@
+module Rscons
+  module Builders
+    # Build a C or C++ source file given a lex (.l, .ll) or yacc (.y, .yy)
+    # input file.
+    #
+    # Examples::
+    #   env.CFile("parser.tab.cc", "parser.yy")
+    #   env.CFile("lex.yy.cc", "parser.ll")
+    class CFile < Builder
+      def default_variables(env)
+        {
+          "YACC" => "bison",
+          "YACC_FLAGS" => ["-d"],
+          "YACC_CMD" => ["${YACC}", "${YACC_FLAGS}", "-o", "${_TARGET}", "${_SOURCES}"],
+          "LEX" => "flex",
+          "LEX_FLAGS" => [],
+          "LEX_CMD" => ["${LEX}", "${LEX_FLAGS}", "-o", "${_TARGET}", "${_SOURCES}"],
+        }
+      end
+
+      def run(target, sources, cache, env, vars)
+        vars = vars.merge({
+          "_TARGET" => target,
+          "_SOURCES" => sources,
+        })
+        cmd =
+          case
+          when sources.first.end_with?(".l", ".ll")
+            "LEX"
+          when sources.first.end_with?(".y", ".yy")
+            "YACC"
+          else
+            raise "Unknown source file #{sources.first.inspect} for CFile builder"
+          end
+        command = env.build_command(env["#{cmd}_CMD"], vars)
+        standard_build("#{cmd} #{target}", target, command, sources, env, cache)
+      end
+    end
+  end
+end