wip for precompile phase for D

Fix up some macOS test cases

.github/workflows/run-tests.yml

@@ -0,0 +1,38 @@
+name: Run RScons Tests
+
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+        ruby-version: ['2.7', '3.0', '3.4']
+    
+    steps:
+    - name: Install dependencies (Linux)
+      if: runner.os == 'Linux'
+      run: sudo apt-get update && sudo apt-get install -y gcc gdc ldc clang flex bison
+
+    - name: Install dependencies (macOS)
+      if: runner.os == 'macOS'
+      run: brew install gcc ldc flex bison
+
+    - name: Checkout repository
+      uses: actions/checkout@v4
+
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby-version }}
+
+    - name: Install dependencies
+      run: bundle install
+
+    - name: Run tests
+      run: rake all

CHANGELOG.md

@@ -1,3 +1,76 @@
+## v3.3.0
+
+### New Features
+
+- Add support for Ruby 3.4.
+- Fix up some macOS test cases.
+- #177 - Remove dependency on base64
+- #175 - Add support for building object files from LLVM assembly sources
+
+## v3.2.0
+
+### New Features
+
+- #171 - Place object files next to source files for source files in build directory
+- #170 - Use top-level build directory as environment build directory for unnamed environments
+- #167 - Add upgrading instructions
+- #166 - Replace CFile builder with Yacc and Lex builders
+
+### Fixes
+
+- #172 - Fix configuration checks performed with ldc2 compiler
+- #169 - Output a better error when pkg-config is not found
+- #168 - Cannot output binary to an environment's build root with the same name as the top-level source directory
+- #164 - Improve DSL method documentation
+
+## v3.1.0
+
+### New Features
+
+- #162 - Improve configuration error messages
+- #163 - Ruby 3.2 compatibility
+
+### Fixes
+
+- #161 - builder registered during build hooks should increase build step count
+
+## v3.0.2
+
+### Fixes
+
+- #159 - Compiler check configure methods should respect :use flag
+- #160 - Configure parameters should not be stored as unscoped construction variables
+
+## v3.0.1
+
+### Fixes
+
+- #156 - Avoid running configure operation twice
+- #157 - Load configure task arguments before early configure operations
+- #158 - Do not configure for clean tasks when not yet configured
+
+## v3.0.0
+
+- #136 - Move rsconscache into build directory
+- #140 - Support naming environments
+- #143 - Add Size builder
+- #142 - Add 'sh' script DSL method
+- #144 - Add FileUtils class methods to script DSL
+- #145 - Support environment variable to set rscons build directory
+- #146 - Add ^^/ shortcut to top-level build directory
+- #139 - Add tasks
+- #147 - Add task options
+- #148 - Add license/copyright to distributable script
+- #150 - Add env.expand() shortcut method to expand paths and construction variables
+- #152 - Add download script method
+- #153 - Allow passing spawn options to sh
+- #154 - Record build directory absolute path
+- #149 - Add shortcut method for creating environments
+- #131 - Only configure if necessary
+- #151 - Store configure task parameters in configuration cache data
+- #137 - Add variants
+- #155 - Add build_dir script method
+
 ## v2.3.0
 
 ### New Features

DEVELOPING.md

@@ -9,6 +9,6 @@ To run the rscons specs, the following commands must be available:
 * g++
 * clang++
 * gdc
-* ldc
+* ldc2
 * flex
 * bison

Gemfile

@@ -1,8 +1,10 @@
 source 'https://rubygems.org'
 
+gem "base64"
 gem "rspec"
 gem "rake"
 gem "simplecov", "~> 0.15.0"
+gem "openssl"
 if RbConfig::CONFIG["host"]["msys"]
   gem "json", "2.1.0"
 else

Gemfile.lock

@@ -1,39 +1,53 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    diff-lcs (1.4.4)
+    base64 (0.3.0)
+    date (3.5.1)
+    diff-lcs (1.6.2)
     docile (1.1.5)
-    json (2.5.1)
-    rake (13.0.6)
-    rdoc (6.3.2)
-    redcarpet (3.5.1)
-    rspec (3.10.0)
-      rspec-core (~> 3.10.0)
-      rspec-expectations (~> 3.10.0)
-      rspec-mocks (~> 3.10.0)
-    rspec-core (3.10.1)
-      rspec-support (~> 3.10.0)
-    rspec-expectations (3.10.1)
+    erb (6.0.1)
+    json (2.18.0)
+    openssl (4.0.0)
+    psych (5.3.1)
+      date
+      stringio
+    rake (13.3.1)
+    rdoc (7.1.0)
+      erb
+      psych (>= 4.0.0)
+      tsort
+    redcarpet (3.6.1)
+    rspec (3.13.2)
+      rspec-core (~> 3.13.0)
+      rspec-expectations (~> 3.13.0)
+      rspec-mocks (~> 3.13.0)
+    rspec-core (3.13.6)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.5)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.10.0)
-    rspec-mocks (3.10.2)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.7)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.10.0)
-    rspec-support (3.10.2)
+      rspec-support (~> 3.13.0)
+    rspec-support (3.13.6)
     simplecov (0.15.1)
       docile (~> 1.1.0)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
+    stringio (3.2.0)
     syntax (1.2.2)
-    yard (0.9.26)
+    tsort (0.2.0)
+    yard (0.9.38)
 
 PLATFORMS
   ruby
   x86-mingw32
 
 DEPENDENCIES
+  base64
   json
+  openssl
   rake
   rdoc
   redcarpet
@@ -43,4 +57,4 @@ DEPENDENCIES
   yard
 
 BUNDLED WITH
-   2.1.4
+   2.6.2

LICENSE.txt

@@ -1,4 +1,4 @@
-Copyright (c) 2013-2022 Josh Holtrop
+Copyright (c) 2013-2025 Josh Holtrop
 
 MIT License
 

README.md

@@ -4,7 +4,39 @@
 
 Rscons (https://github.com/holtrop/rscons) is an open-source build system
 for developers.
+It supports the following features:
 
-Rscons is written in Ruby, and is inspired by [SCons](https://scons.org/) and [waf](https://waf.io/).
+  * multi-threaded job execution
+  * auto-configuration
+  * built-in builders for several common operations
+  * out-of-the-box support for Assembly, C, C++, D, and LLVM
+  * extensibility for other languages or custom builders
+  * compatible with Windows, Linux, OS X, and FreeBSD
+  * colorized output with build progress
+  * build hooks
+  * user-defined tasks with dependencies and custom parameters
+  * build variants
+
+At its core, Rscons is mainly an engine to:
+
+  * determine the proper order to perform build steps,
+  * determine whether each build target is up to date or in need of rebuild, and
+  * schedule those build steps across multiple threads as efficiently as possible.
+
+Along the way, Rscons provides a concise syntax for specifying common types of
+build steps, but also provides an extensible framework for performing
+custom build operations as well.
+
+Rscons takes inspiration from:
+
+  * [SCons](https://scons.org/)
+  * [waf](https://waf.io/)
+  * [rake](https://github.com/ruby/rake)
+  * [CMake](https://cmake.org/)
+  * [Autoconf](https://www.gnu.org/software/autoconf/)
+
+Rscons is written in Ruby.
+The only requirement to run Rscons is that the system has a Ruby interpreter
+installed.
 
 See [https://holtrop.github.io/rscons/index.html](https://holtrop.github.io/rscons/index.html) for User Guide and Installation instructions.

Rakefile.rb

@@ -32,11 +32,12 @@ end
 # useful for coverage information.
 desc "Dist Specs"
 task :dspec, [:example_string] => :build_dist do |task, args|
+  FileUtils.rm_rf("test")
   FileUtils.mkdir_p("test")
   FileUtils.cp("dist/rscons", "test/rscons.rb")
-  ENV["dist_specs"] = "1"
-  Rake::Task["spec"].execute(args.example_string)
-  ENV.delete("dist_specs")
+  ENV["rscons_dist_specs"] = "1"
+  Rake::Task["spec"].execute(args)
+  ENV.delete("rscons_dist_specs")
   FileUtils.rm_f(Dir.glob(".rscons-*"))
 end
 

UPGRADING.md

@@ -0,0 +1,10 @@
+# Upgrading
+
+## v3.2.0
+
+- Replace any calls to `env.CFile()` builder with `env.Lex()` or `env.Yacc()` as required.
+
+## v3.0.0
+
+- Move `build` block contents outside of `build` block and remove `build` call.
+- Replace `Environment.new()` calls with `env()`.

build_tests/cfile/Rsconscript

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

build_tests/cfile/error_unknown_extension.rb

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

build_tests/clone_env/Rsconscript

@@ -1,10 +1,10 @@
-debug = env(echo: :command) do |env|
+debug = env("dbg", echo: :command) do |env|
   env['CFLAGS'] = '-O2'
   env['CPPFLAGS'] = '-DSTRING="Debug Version"'
   env.Program('program-debug.exe', Dir['src/*.c'])
 end
 
-release = debug.clone do |env|
+release = debug.clone("rls") do |env|
   env["CPPFLAGS"] = '-DSTRING="Release Version"'
   env.Program('program-release.exe', Dir['src/*.c'])
 end

build_tests/clone_env/clone_all.rb

@@ -1,4 +1,4 @@
-env1 = env(echo: :command) do |env|
+env1 = env("e1", echo: :command) do |env|
   env['CFLAGS'] = '-O2'
   env.add_build_hook do |builder|
     builder.vars['CPPFLAGS'] = '-DSTRING="Hello"'
@@ -9,6 +9,6 @@ env1 = env(echo: :command) do |env|
   env.Program('program.exe', Dir['src/*.c'])
 end
 
-env2 = env1.clone do |env|
+env2 = env1.clone("e2") do |env|
   env.Program('program2.exe', Dir['src/*.c'])
 end

build_tests/configure/check_c_compiler_use.rb

@@ -0,0 +1,12 @@
+configure do
+  check_c_compiler "clang", use: "clang"
+  check_c_compiler
+end
+
+env "t1" do |env|
+  env.Program("test_gcc.exe", "simple.c")
+end
+
+env "t2", use: "clang" do |env|
+  env.Program("test_clang.exe", "simple.c")
+end

build_tests/configure/check_cfg_no_pkg_config.rb

@@ -0,0 +1,5 @@
+ENV["PATH"] = ""
+
+configure do
+  check_cfg package: "mypackage"
+end

build_tests/configure/check_cxx_compiler_use.rb

@@ -0,0 +1,12 @@
+configure do
+  check_cxx_compiler "clang++", use: "clang"
+  check_cxx_compiler
+end
+
+env "t1" do |env|
+  env.Program("test_gcc.exe", "simple.cc")
+end
+
+env "t2", use: "clang" do |env|
+  env.Program("test_clang.exe", "simple.cc")
+end

build_tests/configure/check_d_compiler_find_first.rb

@@ -1,3 +1,3 @@
 configure do
-  check_d_compiler "gdc", "ldc2"
+  check_d_compiler "gdc", "ldc2", "ldc"
 end

build_tests/configure/check_d_compiler_use.rb

@@ -0,0 +1,12 @@
+configure do
+  check_d_compiler "ldc2", use: "ldc2"
+  check_d_compiler
+end
+
+env "t1" do |env|
+  env.Program("test_gcc.exe", "simple.d")
+end
+
+env "t2", use: "ldc2" do |env|
+  env.Program("test_ldc2.exe", "simple.d")
+end

build_tests/configure/check_lib_with_ldc.rb

@@ -0,0 +1,8 @@
+configure do
+  check_d_compiler "ldc2"
+  check_lib "z"
+end
+
+env(echo: :command) do |env|
+  env.Program("simple.exe", "simple.d")
+end

build_tests/configure/configure_with_top_level_env.rb

@@ -0,0 +1,6 @@
+configure do
+  check_c_compiler
+end
+env do |env|
+  puts "Prefix is #{Task["configure"]["prefix"]}"
+end

build_tests/configure/simple.cc

@@ -0,0 +1,6 @@
+#include <iostream>
+
+int main(int argc, char *argv[])
+{
+    std::cout << "Hi" << std::endl;
+}

build_tests/configure/simple.d

@@ -0,0 +1,7 @@
+import std.stdio;
+
+int main()
+{
+    writeln("Hello");
+    return 0;
+}

build_tests/d/Rsconscript

@@ -3,5 +3,6 @@ configure do
 end
 
 env(echo: :command) do |env|
-  env.Program("hello-d.exe", glob("*.d"))
+  env["D_IMPORT_PATH"] << "src"
+  env.Program("hello-d.exe", glob("src/*.d"))
 end

build_tests/d/build-ldc2.rb

@@ -3,5 +3,6 @@ configure do
 end
 
 env(echo: :command) do |env|
-  env.Program("hello-d.exe", glob("*.d"))
+  env["D_IMPORT_PATH"] << "src"
+  env.Program("hello-d.exe", glob("src/*.d"))
 end

build_tests/d/link_objects.rb

@@ -1,5 +1,6 @@
 env(echo: :command) do |env|
-  env.Object("main.o", "main.d")
-  env.Object("mod.o", "mod.d")
+  env["LD_LIBRARY_PATH"] << "src"
+  env.Object("main.o", "src/main.d")
+  env.Object("mod.o", "src/mod.d")
   env.Program("hello-d.exe", ["main.o", "mod.o"])
 end

build_tests/lex_yacc/Rsconscript

@@ -0,0 +1,4 @@
+env do |env|
+  env.Lex("lexer.c", "lexer.l")
+  env.Yacc("parser.c", "parser.y")
+end

build_tests/library/Rsconscript

@@ -1,4 +1,7 @@
 env(echo: :command) do |env|
-  env.Program('library.exe', ['lib.a', 'three.c'])
-  env.Library("lib.a", ['one.c', 'two.c'], 'CPPFLAGS' => ['-Dmake_lib'])
+  env["LIBS"] << "mylib"
+  env["LIBPATH"] << "."
+  env.Program("library.exe", "one.c")
+  env.depends("library.exe", "libmylib.a")
+  env.Library("libmylib.a", ["two.c", "three.c"], "CPPFLAGS" => ["-Dmake_lib"])
 end

build_tests/library/one.c

@@ -1,8 +1,11 @@
 #include <stdio.h>
 
-#ifdef make_lib
+void two();
+void three();
+
 int main(int argc, char *argv[])
 {
+    two();
     printf("Library\n");
+    three();
 }
-#endif

build_tests/library/override_arcmd.rb

@@ -1,4 +1,4 @@
 env(echo: :command) do |env|
-  env["ARCMD"] = %w[ar rcf ${_TARGET} ${_SOURCES}]
+  env["ARCMD"] = %w[ar rc ${_TARGET} ${_SOURCES}]
   env.Library("lib.a", glob("*.c"))
 end

build_tests/library/three.c

@@ -0,0 +1,3 @@
+void three(void)
+{
+}

build_tests/library/two.c

@@ -0,0 +1,3 @@
+void two(void)
+{
+}

build_tests/llvm/Rsconscript

@@ -0,0 +1,4 @@
+env do |env|
+  env["LLVMAS_FLAGS"] += %w[-Wno-override-module]
+  env.Program("llvmtest.exe", %w[main.c one.ll])
+end

build_tests/llvm/direct.rb

@@ -0,0 +1,8 @@
+configure do
+  check_c_compiler "clang"
+end
+
+env do |env|
+  env["LLVMAS_FLAGS"] += %w[-Wno-override-module]
+  env.Program("llvmtest.exe", %w[one.ll two.ll main2.c], direct: true)
+end

build_tests/llvm/main.c

@@ -0,0 +1,6 @@
+extern int one(void);
+
+int main(int argc, char * argv[])
+{
+    return one();
+}

build_tests/llvm/main2.c

@@ -0,0 +1,9 @@
+extern int one(void);
+extern int two(void);
+
+int main(int argc, char * argv[])
+{
+    one();
+    two();
+    return 0;
+}

build_tests/llvm/one.ll

@@ -0,0 +1,9 @@
+@str = private unnamed_addr constant [12 x i8] c"hello world\00"
+
+declare i32 @puts(ptr nocapture) nounwind
+
+define i32 @one()
+{
+    call i32 @puts(ptr @str)
+    ret i32 0
+}

build_tests/llvm/two.ll

@@ -0,0 +1,9 @@
+@str = private unnamed_addr constant [12 x i8] c"hello again\00"
+
+declare i32 @puts(ptr nocapture) nounwind
+
+define i32 @two()
+{
+    call i32 @puts(ptr @str)
+    ret i32 0
+}

build_tests/simple/build_root_source_path.rb

@@ -0,0 +1,13 @@
+env("e", echo: :command) do |env|
+  source_file = "#{env.build_root}/src/foo.c"
+  FileUtils.mkdir_p(File.dirname(source_file))
+  File.open(source_file, "w") do |fh|
+    fh.puts(<<-EOF)
+    int main()
+    {
+      return 29;
+    }
+    EOF
+  end
+  env.Program("foo.exe", source_file)
+end

build_tests/simple/builder_wait_for_builder.rb

@@ -1,7 +1,7 @@
 class MyObject < Rscons::Builder
   def run(options)
     if @builder
-      if File.exists?(@target)
+      if File.exist?(@target)
         true
       else
         false

build_tests/simple/clean.rb

@@ -0,0 +1,7 @@
+env do |env|
+  env.Program('simple.exe', Dir['*.c'])
+end
+
+clean do
+  puts "custom clean action"
+end

build_tests/simple/env_in_task.rb

@@ -0,0 +1,5 @@
+default do
+  env do |env|
+    env.Program('simple.exe', Dir['*.c'])
+  end
+end

build_tests/simple/link_flag_change.rb

@@ -1,5 +1,6 @@
 env(echo: :command) do |env|
   env["LD"] = "gcc"
+  mkdir_p("libdir")
   env["LIBPATH"] += ["libdir"]
   env.Program('simple.exe', Dir['*.c'])
 end

build_tests/simple/user_dep_build_order.rb

@@ -4,7 +4,7 @@ class TestBuilder < Rscons::Builder
       true
     else
       if @target == "two"
-        return false unless File.exists?("one")
+        return false unless File.exist?("one")
       end
       wait_time = @env.expand_varref("${wait_time}", @vars)
       @command = ["ruby", "-e", "require 'fileutils'; sleep #{wait_time}; FileUtils.touch('#{@target}');"]

build_tests/two_sources/assuffix.rb

@@ -3,5 +3,5 @@ env do |env|
   env["CFLAGS"] += %w[-S]
   env.Object("one.ssss", "one.c", "CPPFLAGS" => ["-DONE"])
   env.Object("two.sss", "two.c")
-  env.Program("two_sources.exe", %w[one.ssss two.sss], "ASFLAGS" => env["ASFLAGS"] + %w[-x assembler])
+  env.Program("two_sources.exe", %w[one.ssss two.sss], "ASFLAGS" => env["ASFLAGS"] + %w[-x assembler-with-cpp])
 end

build_tests/two_sources/two.c

@@ -1,3 +1,6 @@
 #ifdef ONE
 #error ONE should not be defined
 #endif
+void two(void)
+{
+}

build_tests/typical/binary_matching_folder.rb

@@ -0,0 +1,4 @@
+env "src" do |env|
+  env["CPPPATH"] += glob("src/**")
+  env.Program("^/src", glob("src/**/*.c"))
+end

build_tests/typical/build_dir.rb

@@ -0,0 +1,3 @@
+default do
+  touch "#{build_dir}/a.file"
+end

build_tests/typical/phonies.rb

@@ -0,0 +1,15 @@
+class Custom < Rscons::Builder
+  def run(options)
+    print_run_message("#{name} #{target}", nil)
+    true
+  end
+end
+
+env do |env|
+  env.add_builder(Custom)
+  env.Custom("t3", :phony1)
+  env.Custom(:phony1, "t2")
+  env.Custom("t2", :phony2)
+  env.Custom(:phony2, "t1")
+  env.Custom("t1", [])
+end

build_tests/variants/error_unnamed_environment.rb

@@ -0,0 +1,13 @@
+variant "debug"
+variant "release"
+
+with_variants do
+  env do |env|
+    if variant("debug")
+      env["CPPDEFINES"] << "DEBUG"
+    else
+      env["CPPDEFINES"] << "NDEBUG"
+    end
+    env.Program("^/prog.exe", "prog.c")
+  end
+end

build_tests/variants/variant_enabled.rb

@@ -0,0 +1,14 @@
+variant "one"
+variant "two", default: false
+
+configure do
+  if variant_enabled?("one")
+    puts "one enabled"
+  end
+  if variant_enabled?("two")
+    puts "two enabled"
+  end
+  if variant_enabled?("three")
+    puts "three enabled"
+  end
+end

doc/user_guide.md

@@ -6,12 +6,13 @@ It supports the following features:
   * multi-threaded job execution
   * auto-configuration
   * built-in builders for several common operations
-  * out-of-the-box support for C, C++, and D languages
+  * out-of-the-box support for Assembly, C, C++, D, and LLVM
   * extensibility for other languages or custom builders
   * compatible with Windows, Linux, OS X, and FreeBSD
   * colorized output with build progress
   * build hooks
   * user-defined tasks with dependencies and custom parameters
+  * build variants
 
 At its core, Rscons is mainly an engine to:
 
@@ -67,8 +68,8 @@ incorrect decision being made to not rebuild when a rebuild is necessary.
 ### Build Flexibility
 
 Rscons supports multiple configurations of compilation flags or build options
-across multiple environments to build output files in different ways according
-to the user's desire.
+across multiple environments or build variants to build output files in
+different ways according to the user's desire.
 For example, the same source files can be built into a release executable, but
 also compiled with different compilation flags or build options into a test
 executable.
@@ -143,17 +144,52 @@ different version control systems):
 
 Rscons is typically invoked from the command-line as `./rscons`.
 
-    ./rscons [global options] [[task] [task options] ...]
+    Usage: ./rscons [global options] [[task] [task options] ...]
 
     Global options:
-      -b BUILD, --build=BUILD     Set build directory (default: build)
-      -f FILE                     Use FILE as Rsconscript
-      -F, --show-failure          Show failed command log from previous build and exit
-      -h, --help                  Show rscons help and exit
-      -j N, --nthreads=N          Set number of threads
-      -r COLOR, --color=COLOR     Set color mode (off, auto, force)
-      -v, --verbose               Run verbosely
-      --version                   Show rscons version and exit
+      -A, --all
+        Show all tasks (even those without descriptions) in task list. Use in
+        conjunction with the -T argument.
+
+      -b BUILD, --build=BUILD
+        Set build directory (default: build).
+
+      -e VS, --variants=VS
+        Enable or disable variants. VS is a comma-separated list of variant
+        entries. If the entry begins with "-" the variant is disabled instead of
+        enabled. If the full list begins with "+" or "-" then it modifies the
+        variants that are enabled by default by only enabling or disabling the
+        listed variants. Otherwise, the enabled set of variants is as given and
+        any variants not listed are disabled. The set of enabled variants is
+        remembered from when the project is configured.
+
+      -f FILE
+        Use FILE as Rsconscript.
+
+      -F, --show-failure
+        Show failed command log from previous build and exit (does not load build
+        script).
+
+      -h, --help
+        Show rscons help and exit (does not load build script).
+
+      -j N, --nthreads=N
+        Set number of threads (local default: 16).
+
+      -r COLOR, --color=COLOR
+        Set color mode (off, auto, force).
+
+      -T, --tasks
+        Show task list and parameters and exit (loads build script). By default
+        only tasks with a description are listed. Use -AT to show all tasks whether
+        they have a description or not.
+
+      -v, --verbose
+        Run verbosely. This causes Rscons to print the full build command used by
+        each builder.
+
+      --version
+        Show rscons version and exit (does not load build script).
 
 The user can list any number of tasks on the command line.
 Any parameters beginning with a "-" that follow a task are interpreted as task
@@ -181,6 +217,19 @@ Rscons execution.
 The user can also invoke Rscons with the `-v` global command-line option which
 will cause Rscons to print each command it is executing.
 
+## Rscons Operation Phases
+
+When Rscons executes, it performs the following phases:
+
+  - Parse the command line.
+    - This is the last step if --help, --version, or --show-failure is specified.
+  - Load the build script.
+    - This is the last step if --tasks is specified.
+  - Configure the project by running the `configure` task if necessary (the
+    project has not yet been configured, autoconf is set to true, and the user
+    is requesting to execute a task that is marked with autoconf set to true)
+  - Execute user-requested tasks.
+
 #> The Build Script
 
 Rscons looks for instructions for what to build by reading a build script file
@@ -188,10 +237,8 @@ called `Rsconscript` (or `Rsconscript.rb`).
 Here is a simple example `Rsconscript` file:
 
 ```ruby
-default do
-  Environment.new do |env|
-    env.Program("myprog.exe", glob("src/**/*.c"))
-  end
+env do |env|
+  env.Program("myprog.exe", glob("src/**/*.c"))
 end
 ```
 
@@ -203,7 +250,7 @@ The `Rsconscript` file is a Ruby script.
 
 ##> Tasks
 
-Tasks are the high-level user interface for performing functionality in a build
+Tasks are a high-level user interface for performing functionality in a build
 script.
 Tasks can create Environments that perform compilation/linking steps.
 Tasks can also execute arbitrary commands or perform any miscellaneous logic.
@@ -218,21 +265,17 @@ which they were added.
 Example:
 
 ```ruby
-task "build" do
-  Environment.new do |env|
-    env.Program("^^/proj.elf", glob("src/**/*.c"))
-  end
+proj_env = env do |env|
+  env.Program("^/proj.elf", glob("src/**/*.c"))
 end
 
-task "flash", deps: "build" do
-  sh "nrfjprog", "-f", "NRF52", "--program", env.expand("^^/proj.elf")
+task "flash" do
+  sh "nrfjprog", "-f", "NRF52", "--program", proj_env.expand("^/proj.elf")
 end
 ```
 
-In this example, the `flash` task depends on the `build` task.
-So if the project had not yet been built, and the user executes
-`./rscons flash`, the project would first be built and then flashed to the
-target.
+In this example, the `flash` task would first build the proj.elf target and
+then flash it to target with the nrfjprog program.
 
 If the `task` method is called again with the name of an already existing task,
 the task is not overwritten, but rather modified.
@@ -240,9 +283,41 @@ Any newly specified dependencies are added to the current dependencies.
 Any action block is appended to the task's list of action blocks to execute
 when the task is executed.
 
+For example, with the `Rsconscript`:
+
+```ruby
+task "a" do
+  puts "A"
+end
+
+task "b" do
+  puts "B"
+end
+
+task "c", depends: "a" do
+  puts "C1"
+end
+
+task "c", depends: "b" do
+  puts "C2"
+end
+```
+
+The following behavior is observed:
+
+    $ ./rscons c
+    A
+    B
+    C1
+    C2
+
+Note that for a simple project, the build script may not need to define any
+tasks at all and could just make use of the Rscons built-in default task (see
+${#Default Task}).
+
 ###> Task Parameters
 
-Tasks can also take parameters.
+Tasks can accept parameters.
 Parameters are defined by the build script author, and have default values.
 The user can override parameter values on the command line.
 
@@ -261,7 +336,7 @@ task "build", params: [
   param("myparam", "defaultvalue", true, "My special parameter"),
   param("xyz", nil, false, "Enable the xyz feature"),
 ] do |task, params|
-  Environment.new do |env|
+  env do |env|
     env["CPPDEFINES"] << "SOMEMACRO=#{params["myparam"]}"
     if params["flag"]
       env["CPPDEFINES"] << "ENABLE_FEATURE_XYZ"
@@ -327,7 +402,7 @@ argument (task name) automatically filled in by the shortcut method.
 For example:
 
 ```ruby
-default deps: "unpack_compiler" do
+default depends: "unpack_compiler" do
   puts "default task"
 end
 ```
@@ -335,7 +410,7 @@ end
 is equivalent to:
 
 ```ruby
-task "default", deps: "unpack_compiler" do
+task "default", depends: "unpack_compiler" do
   puts "default task"
 end
 ```
@@ -395,12 +470,13 @@ end
 See ${#Configuring the Project} for more details on how to make use of the
 configuration functionality that Rscons provides.
 
+Configure blocks must be defined in the Rsconscript file before any
+environments are created.
+
 ####> Default Task
 
 The `default` task is special in that Rscons will execute it if no other task
 has been requested by the user on the command line.
-It is entirely feasible for the default task to be the only task defined for a
-project, and simple projects may wish to do just that.
 
 The default task can also be used to declare a dependency on another task that
 would effectively become the default.
@@ -411,11 +487,11 @@ task "build" do
   ...
 end
 
-task "flash" do
+task "flash", depends: "build" do
   ...
 end
 
-default deps: "build"
+default depends: "build"
 ```
 
 Then when the user runs `./rscons` the "build" task will be executed.
@@ -432,7 +508,8 @@ It will not remove the cached configuration options.
 The `distclean` task is built-in to Rscons.
 It removes all built target files and all cached configuration options.
 Generally it will get the project directory back to the state it was in when
-unpacked before any configuration or build operations took place.
+unpacked or checked out, before any configuration or build operations took
+place.
 It will not remove items installed by an Install builder.
 
 ####> Install Task
@@ -734,17 +811,18 @@ If set, a build define of the specified String will be added to the
 ##> Building Targets
 
 Building target files is accomplished by using Environments.
-Environments are typically created within the default task or any user-defined
-tasks.
+Environments can be created at the top level of the build script, or from
+within a task action block.
 
-Here is an example `default` task block demonstrating how to create an
-Environment and register a build target:
+Environments are created with the
+[`env`](../yard/Rscons/Script/GlobalDsl.html#env-instance_method) build script
+method.
+Here is an example build script that creates an Environment and registers a
+Program build target:
 
 ```ruby
-default do
-  Environment.new do |env|
-    env.Program("myprog.exe", glob("src/**/*.c"))
-  end
+env do |env|
+  env.Program("myprog.exe", glob("src/**/*.c"))
 end
 ```
 
@@ -759,24 +837,21 @@ An Environment includes:
   - a collection of construction variables
   - a collection of build hooks
   - a collection of user-registered build targets
-  - a build root
+  - a build root directory
 
 All build targets must be registered within an `Environment`.
 If the user does not specify a name for the environment, a name will be
 automatically generated based on the Environment's internal ID, for example
 "e.1".
-The Environment's build root is a directory created within the top-level
-Rscons build directory.
-It is based on the Environment name.
+The Environment's build root is a directory with the same name as the
+Environment, created within the top-level Rscons build directory.
 By default it holds all intermediate files generated by Rscons that are needed
 to produce a user-specified build target.
 For example, for the `Rsconscript`:
 
 ```ruby
-default do
-  Environment.new(name: "myproj") do |env|
-    env.Program("myprog.exe", glob("src/**/*.c"))
-  end
+env "myproj" do |env|
+  env.Program("myprog.exe", glob("src/**/*.c"))
 end
 ```
 
@@ -786,6 +861,12 @@ Assuming a top-level build directory of "build", the Environment's build root
 would be "build/myproj".
 This keeps the intermediate generated build artifacts separate from the source
 files.
+Source and target paths passed to a Builder (e.g. Program) can begin with "^/"
+to indicate that Rscons should expand those paths to be relative to the
+Environment's build root.
+If a source or target path passed to a Builder begins with "^^/", it is
+expanded to be relative to the Rscons top-level build directory (but outside
+the Environment's build root).
 
 ###> Construction Variables
 
@@ -797,11 +878,9 @@ construction variables.
 Example:
 
 ```ruby
-default do
-  Environment.new do |env|
-    env["CCFLAGS"] += %w[-O2 -Wall]
-    env["LIBS"] += %w[m]
-  end
+env do |env|
+  env["CCFLAGS"] += %w[-O2 -Wall]
+  env["LIBS"] += %w[m]
 end
 ```
 
@@ -813,6 +892,7 @@ It also instructs the linker to link against the `m` library.
 
   * uppercase strings - the default construction variables that Rscons uses
   * strings beginning with "_" - set and used internally by builders
+  * lowercase strings with a ":" as "#{task_name}:#{parameter_name}" - set to task parameter values
   * symbols, lowercase strings - reserved as user-defined construction variables
 
 ###> Builders
@@ -834,7 +914,8 @@ The `target` parameter is the path to the output file or directory.
 The `sources` parameter is the path or paths to the input file(s) to be used
 by the builder.
 In the `target` and `sources` parameters, the user can explicitly refer to a
-path within the Environment's build root by beginning the path with "^/".
+path within the Environment's build root by beginning the path with "^/", or to
+a path within the Rscons top-level built directory by beginning with "^^/".
 The `vars` parameter is an optional Hash which can include construction
 variables to be used for this build target.
 Any construction variable values specified in this parameter will override
@@ -844,11 +925,11 @@ There are several default builders that are built-in to Rscons:
 
   * `Command`, which executes a user-defined command to produce the target.
   * `Copy`, which copies files or directories to a specified destination.
-  * `CFile`, which builds a C or C++ source file from a lex or yacc input file.
   * `Directory`, which creates a directory.
   * `Disassemble`, which disassembles an object file to a disassembly listing.
   * `Install`, which installs files or directories to a specified destination.
   * `InstallDirectory`, which creates a directory in an install destination.
+  * `Lex`, which builds a source file from a lex input file.
   * `Library`, which collects object files into a static library archive file.
   * `Object`, which compiles source files to produce an object file.
   * `Preprocess`, which invokes the C/C++ preprocessor on a source file.
@@ -858,6 +939,7 @@ There are several default builders that are built-in to Rscons:
   * `SharedObject`, which compiles source files to produce an object file, in a
     way that is able to be used to create a shared library.
   * `Size`, which runs the 'size' utility on an executable file.
+  * `Yacc`, which builds a source file from a yacc input file.
 
 ####> The Command Builder
 
@@ -884,17 +966,6 @@ The `Command` builder supports the following construction variables:
     `CMD_STDOUT` is expanded for variable references, so the token `${_TARGET}`
     can be used, for example.
 
-####> The CFile Builder
-
-```ruby
-env.CFile(target, source)
-# Example
-env.CFile("^/parser/parser.c", "parser.y")
-```
-
-The `CFile` builder will generate a C or C++ source file from a lex (.l, .ll)
-or yacc (.y, .yy) input file.
-
 ####> The Copy Builder
 
 ```ruby
@@ -967,6 +1038,17 @@ the `InstallDirectory` builder.
 The `uninstall` task removes targets created by the `InstallDirectory` builder
 but not by the `Directory` builder.
 
+####> The Lex Builder
+
+```ruby
+env.Lex(target, source)
+# Example
+env.Lex("^/lexer.c", "lexer.l")
+```
+
+The `Lex` builder will generate a source file from a lex (.l, .ll)
+input file.
+
 ####> The Library Builder
 
 ```ruby
@@ -1097,9 +1179,20 @@ stores its output in the target file.
 The size executable can be specified with the `SIZE` construction variable,
 and flags can be specified with `SIZEFLAGS`.
 
+####> The Yacc Builder
+
+```ruby
+env.Yacc(target, source)
+# Example
+env.Yacc("^/parser.c", "parser.y")
+```
+
+The `Yacc` builder will generate a source file from a yacc (.y, .yy)
+input file.
+
 ###> Phony Targets
 
-rscons supports phony build targets.
+Rscons supports phony build targets.
 Normally, a builder produces an output file, and executes whenever the input
 files or command have changed.
 A phony build target can be used to register a builder that does not produce
@@ -1142,17 +1235,15 @@ build target or source file names.
 Example:
 
 ```ruby
-default do
-  Environment.new do |env|
-    env["CFLAGS"] << "-Wall"
-    env.add_build_hook do |builder|
-      # Compile sources from under src/tests without the -Wall flag.
-      if builder.sources.first =~ %r{src/tests/}
-        builder.vars["CFLAGS"] -= %w[-Wall]
-      end
+env do |env|
+  env["CFLAGS"] << "-Wall"
+  env.add_build_hook do |builder|
+    # Compile sources from under src/tests without the -Wall flag.
+    if builder.sources.first =~ %r{src/tests/}
+      builder.vars["CFLAGS"] -= %w[-Wall]
     end
-    env.Program("program.exe", glob("src/**/*.c"))
   end
+  env.Program("program.exe", glob("src/**/*.c"))
 end
 ```
 
@@ -1166,7 +1257,7 @@ Build hooks and post-build hooks can register new build targets.
 
 ###> Barriers
 
-Normally Rscons will parallelize all builders.
+Normally Rscons will parallelize all builders executed within an Environment.
 A barrier can be used to separate sets of build targets.
 All build targets registered before the barrier is created will be built before
 Rscons will schedule any build targets after the barrier.
@@ -1176,14 +1267,140 @@ In other words, build targets are not parallelized across a barrier.
 env.barrier
 ```
 
+##> Variants
+
+Rscons supports build variants.
+Variants can be used to built multiple variations of the same item with a
+specific change.
+For example, a desktop application with the same sources could be built to
+target KDE or GNOME using build variants.
+It is up to the build script author to define the variants and what effect they
+have on the build.
+
+This build script defines "kde" and "gnome" variants:
+
+```ruby
+variant "kde"
+variant "gnome"
+
+with_variants do
+  env "prog" do |env|
+    if variant "kde"
+      env["CPPDEFINES"] << "KDE"
+    end
+    if variant "gnome"
+      env["CPPDEFINES"] << "GNOME"
+    end
+    env.Program("^/prog.exe", "src/**/*.cpp")
+  end
+end
+```
+
+The `variant` build script method has two uses:
+
+  * At the top of the build script, it defines a variant.
+  * Within a `with_variants` block, it queries for whether the given variant is
+    active.
+
+The `with_variants` build script method allows the power of variants to be
+harnessed.
+It iterates through each enabled variant and calls the given block.
+In this example, the block would be called twice, once with the "kde" variant
+active, and the second time with the "gnome" variant active.
+
+Each `env` method call creates an Environment, so two environments are created.
+When an Environment is created within a `with_variants` block, the
+Environment's build directory name has the active variant(s) keys appended to
+the given Environment name, and separated by a "-".
+
+In this example, a "prog-kde" Environment would be created with build root
+build/prog-kde and -DKDE would be passed to the compiler when compiling each
+source.
+Next a "prog-gnome" Environment would be created with build root
+build/prog-gnome and -DGNOME would be passed to the compiler when compiling
+the sources.
+
+The key for a variant is the variant's name by default but can be overridden by
+passing a `:key` value to the `variant` method.
+A `nil` value for the `:key` parameter will omit that variant from appearing
+in the environment's build directory name.
+For example:
+
+```ruby
+variant "debug"
+variant "release", key: nil
+
+with_variants do
+  env "prog" do |env|
+  end
+end
+```
+
+In this example, one "prog" environment will be created for the "debug" variant
+with the build directory "prog-debug", and another "prog" environment will be
+created for the "release" variant with the build directory "prog".
+The build directory for the release variant of the "prog" environment is just
+"prog" instead of "prog-release" because the key for the "release" variant is
+set to `nil`.
+
+Variants are enabled by default, but can be disabled by passing a `false` value
+to the `:default` option of the `variant` method.
+For example:
+
+```ruby
+${include build_tests/variants/default.rb}
+```
+
+The `rscons` command line interface provides a `-e`/`--variants` argument which
+allows the user to enable a different set of variants from those enabled by
+default according to the build script author.
+This argument accepts a comma-separated list of variants to enable.
+Each entry in the list can begin with "-" to disable the variant instead of
+enable it.
+If the list begins with "+" or "-", then the entire given list modifies the
+defaults given in the build script.
+Otherwise, it exactly specifies which variants should be enabled, and any
+variant not listed is disabled.
+
+When the project is configured, the set of enabled variants is recorded and
+remembered for later Rscons invocations.
+This way, a user working on a single variant of a project does not need to
+specify the `-e`/`--variants` option on each build operation.
+
+The `variant_enabled?` build script method can be called to query whether the
+given variant is enabled.
+
+###> Variant Groups
+
+Variants may be grouped, which allows the build script author to define
+multiple combinations of desired variations to build with.
+For example:
+
+```ruby
+${include build_tests/variants/multiple_groups.rb}
+```
+
+This build script executes the block given to `with_variants` four times and
+results in four Environments being created:
+
+  * prog-kde-debug
+  * prog-kde-release
+  * prog-gnome-debug
+  * prog-gnome-release
+
+The command `./rscons -e-debug` would build just "prog-kde-release" and "prog-gnome-release".
+The command `./rscons --variants kde,release` would build just "prog-kde-release".
+
 ##> Build Script Methods
 
 `rscons` provides several methods that a build script can use.
 
   * `autoconf` (see ${#Configure Task})
+  * `build_dir` which returns the path to the top-level Rscons build directory
   * `clean` (see ${#Clean Task})
   * `configure` (see ${#Configure Task})
   * `default` (see ${#Default Task})
+  * `download` (see ${#Downloading Files: The download Method})
   * `distclean` (see ${#Distclean Task})
   * `glob` (see ${#Finding Files: The glob Method})
   * `install` (see ${#Install Task})
@@ -1197,6 +1414,10 @@ env.barrier
   * `sh` (see (${#Executing Commands: The sh Method})
   * `task` (see ${#Tasks})
   * `uninstall` (see ${#Uninstall Task})
+  * `variant` (see ${#Variants})
+  * `variant_enabled?` (see ${#Variant Groups})
+  * `variant_group` (see ${#Variant Groups})
+  * `with_variants` (see ${#Variant Groups})
 
 Additionally, the following methods from the Ruby
 [FileUtils](https://ruby-doc.org/stdlib-3.1.0/libdoc/fileutils/rdoc/FileUtils.html)
@@ -1237,16 +1458,39 @@ rather than file system directory ordering).
 Example use:
 
 ```ruby
-default do
-  Environment.new do |env|
-    env.Program("mytests", glob("src/**/*.cc", "test/**/*.cc"))
-  end
+env do |env|
+  env.Program("mytests", glob("src/**/*.cc", "test/**/*.cc"))
 end
 ```
 
 This example would build the `mytests` executable from all `.cc` source files
 found recursively under the `src` or `test` directory.
 
+###> Downloading Files: The download Method
+
+The [`download`](../yard/Rscons/Script/GlobalDsl.html#download-instance_method)
+method can be used to download a file from a given URL.
+
+Example use:
+
+```ruby
+default do
+  download "https://ftp.gnu.org/gnu/gcc/gcc-#{gcc_version}/gcc-#{gcc_version}.tar.xz",
+    "#{build_dir}/gcc-#{gcc_version}.tar.xz",
+    sha256_sum: gcc_checksum
+end
+```
+
+The `download` method downloads the file specified by the URL in the first
+parameter, and writes it to the local file specified by the second parameter.
+If the `:sha256sum` option is given, this causes two changes to the default
+behavior:
+
+  * If Rscons finds the local file and it already has this checksum, then the
+    file will not be downloaded again.
+  * After downloading, Rscons verifies that the checksum matches what is given
+    and exits with an error if it does not.
+
 ###> PATH Management
 
 `rscons` provides methods for management of the `PATH` environment variable.
@@ -1354,6 +1598,18 @@ default do
 end
 ```
 
+Options that Ruby's `spawn` method accepts can also be passed in to the `sh`
+method.
+For example, to execute the given command with a different working directory,
+the `:chdir` option can be specified:
+
+```ruby
+default do
+  # Execute 'ls' from within the 'src' directory:
+  sh "ls", chdir: "src"
+end
+```
+
 ##> Extending Rscons
 
 ### Adding New Languages
@@ -1361,8 +1617,8 @@ end
 The `Object` and `SharedObject` builders that ship with Rscons have an API that
 allows the user to register extra languages that can be suppored by the
 builders.
-In fact, the built-in support for assembly, C, C++, and D compilation all make
-use of this built-in API.
+In fact, the built-in support for assembly, C, C++, D, and LLVM compilation
+all make use of this built-in API.
 To see an example of how this API is used, see the
 `lib/rscons/builders/lang/*.rb` files in the Rscons source repository.
 For example, here is how the C++ language is registered:
@@ -1406,7 +1662,7 @@ class Rscons::Builders::Mine < Rscons::Builder
 end
 
 default do
-  Environment.new do |env|
+  env do |env|
     env.add_builder(Rscons::Builders::Mine)
   end
 end
@@ -1429,7 +1685,7 @@ Rscons::DEFAULT_BUILDERS << :Special
 load "SpecialBuilder.rb"
 
 default do
-  Environment.new do |env|
+  env do |env|
     # A build target using the "Special" builder can be registered.
     env.Special("target", "source")
   end
@@ -1656,40 +1912,45 @@ ${include lib/rscons/default_construction_variables.rb}
 ### Example: Building a C Program
 
 ```ruby
-default do
-  Environment.new do |env|
-    env["CFLAGS"] << "-Wall"
-    env.Program("program", glob("src/**/*.c"))
-  end
+env do |env|
+  env["CFLAGS"] << "-Wall"
+  env.Program("program", glob("src/**/*.c"))
 end
 ```
 
 ### Example: Building a D Program
 
 ```ruby
-default do
-  Environment.new do |env|
-    env["DFLAGS"] << "-Wall"
-    env.Program("program", glob("src/**/*.d"))
-  end
+env do |env|
+  env["DFLAGS"] << "-Wall"
+  env.Program("program", glob("src/**/*.d"))
+end
+```
+
+### Example: Building a Program from C and LLVM Sources
+
+```ruby
+env do |env|
+  env["CFLAGS"] << "-Wall"
+  env.Program("program", glob("src/**/*.{c,ll}"))
 end
 ```
 
 ### Example: Cloning an Environment
 
 ```ruby
-default do
-  main_env = Environment.new do |env|
-    env["CFLAGS"] = ["-DSOME_DEFINE", "-O3"]
-    env["LIBS"] = ["SDL"]
-    env.Program("program", glob("src/**/*.cc"))
-  end
+main_env = env do |env|
+  env["CFLAGS"] = ["-fshort-enums", "-O3"]
+  env["CPPDEFINES"] << "SOME_DEFINE"
+  env["LIBS"] = ["SDL"]
+  env.Program("program", glob("src/**/*.cc"))
+end
 
-  debug_env = main_env.clone do |env|
-    env["CFLAGS"] -= ["-O3"]
-    env["CFLAGS"] += ["-g", "-O0"]
-    env.Program("program-debug", glob("src/**/*.cc"))
-  end
+test_env = main_env.clone do |env|
+  env["CFLAGS"] -= ["-O3"]
+  env["CFLAGS"] += ["-g", "-O0"]
+  env["CPPDEFINES"] = "ENABLE_TESTS"
+  env.Program("program-test", glob("src/**/*.cc"))
 end
 ```
 
@@ -1709,49 +1970,123 @@ EOF
   end
 end
 
-default do
-  Environment.new do |env|
-    env.add_builder(GenerateFoo)
-    env.GenerateFoo("foo.h", [])
-    env.Program("a.out", glob("*.c"))
-  end
+env do |env|
+  env.add_builder(GenerateFoo)
+  env.GenerateFoo("foo.h", [])
+  env.Program("a.out", glob("*.c"))
 end
 ```
 
 ### Example: Using different compilation flags for some sources
 
 ```ruby
-default do
-  Environment.new do |env|
-    env["CFLAGS"] = ["-O3", "-Wall"]
-    env.add_build_hook do |builder|
-      if builder.sources.first =~ %r{src/third-party/}
-        build_op[:vars]["CFLAGS"] -= ["-Wall"]
-      end
+env do |env|
+  env["CFLAGS"] = ["-O3", "-Wall"]
+  env.add_build_hook do |builder|
+    if builder.sources.first =~ %r{src/third-party/}
+      build_op[:vars]["CFLAGS"] -= ["-Wall"]
     end
-    env.Program("program", glob("**/*.cc"))
   end
+  env.Program("program", glob("**/*.cc"))
 end
 ```
 
 ### Example: Creating a static library
 
 ```ruby
-default do
-  Environment.new do |env|
-    env.Library("mylib.a", glob("src/**/*.c"))
-  end
+env do |env|
+  env.Library("mylib.a", glob("src/**/*.c"))
 end
 ```
 
 ### Example: Creating a C++ parser source from a Yacc/Bison input file
 
 ```ruby
+env do |env|
+  env.Yacc("^/parser.tab.cc", "parser.yy")
+end
+```
+
+### Example: GCC Cross Compiler
+
+```ruby
+binutils_version = "2.35"
+binutils_checksum = "1b11659fb49e20e18db460d44485f09442c8c56d5df165de9461eb09c8302f85"
+gcc_version = "10.2.0"
+gcc_checksum = "b8dd4368bb9c7f0b98188317ee0254dd8cc99d1e3a18d0ff146c855fe16c1d8c"
+install_path = File.expand_path("i686-elf-gcc")
+target = "i686-elf"
+path_prepend "#{install_path}/bin"
+
+configure do
+  check_c_compiler "gcc"
+  check_program "make"
+  check_program "bison"
+  check_program "flex"
+  check_program "texi2any", on_fail: "Install the texinfo package"
+  check_program "wget"
+  check_lib "gmp", on_fail: "Install the libgmp-dev package"
+  check_lib "mpc", on_fail: "Install the libmpc-dev package"
+  check_lib "mpfr", on_fail: "Install the libmpfr-dev package"
+end
+
 default do
-  Environment.new do |env|
-    env.CFile("^/parser.tab.cc", "parser.yy")
+  unless Dir.exist?(install_path)
+
+    # Download archives.
+    download "https://ftp.gnu.org/gnu/binutils/binutils-#{binutils_version}.tar.xz",
+      "#{build_dir}/binutils-#{binutils_version}.tar.xz",
+      sha256sum: binutils_checksum
+
+    download "https://ftp.gnu.org/gnu/gcc/gcc-#{gcc_version}/gcc-#{gcc_version}.tar.xz",
+      "#{build_dir}/gcc-#{gcc_version}.tar.xz",
+      sha256sum: gcc_checksum
+
+    # Extract archives.
+    sh "tar", "xJf", "binutils-#{binutils_version}.tar.xz",
+      chdir: build_dir
+
+    sh "tar", "xJf", "gcc-#{gcc_version}.tar.xz",
+      chdir: build_dir
+
+    # Build binutils.
+    rm_rf "#{build_dir}/build-binutils"
+    mkdir_p "#{build_dir}/build-binutils"
+    cd "#{build_dir}/build-binutils" do
+      sh %W[../binutils-#{binutils_version}/configure
+        --target=#{target} --prefix=#{install_path} --with-sysroot --disable-nls
+        --disable-werror]
+      sh "make"
+      sh "make install"
+    end
+
+    # Build gcc.
+    rm_rf "#{build_dir}/build-gcc"
+    mkdir_p "#{build_dir}/build-gcc"
+    cd "#{build_dir}/build-gcc" do
+      sh %W[../gcc-#{gcc_version}/configure
+        --target=#{target} --prefix=#{install_path} --disable-nls
+        --enable-languages=c,c++ --without-headers]
+      sh "make all-gcc"
+      sh "make all-target-libgcc"
+      sh "make install-gcc"
+      sh "make install-target-libgcc"
+    end
   end
 end
+
+clean do
+  rm_f "#{build_dir}/binutils-#{binutils_version}.tar.xz"
+  rm_rf "#{build_dir}/binutils-#{binutils_version}"
+  rm_rf "#{build_dir}/build-binutils"
+  rm_f "#{build_dir}/gcc-#{gcc_version}.tar.xz"
+  rm_rf "#{build_dir}/gcc-#{gcc_version}"
+  rm_rf "#{build_dir}/build-gcc"
+end
+
+distclean do
+  rm_rf install_path
+end
 ```
 
 ##> ./configure && make

lib/rscons.rb

@@ -23,20 +23,23 @@ module Rscons
   # Names of the default builders which will be added to all newly created
   # {Environment} objects.
   DEFAULT_BUILDERS = [
-    :CFile,
+    :Barrier,
     :Command,
     :Copy,
     :Directory,
     :Disassemble,
     :Install,
     :InstallDirectory,
+    :Lex,
     :Library,
     :Object,
+    :Precompile,
     :Preprocess,
     :Program,
     :SharedLibrary,
     :SharedObject,
     :Size,
+    :Yacc,
   ]
 
   # Class to represent a fatal error during an Rscons operation.
@@ -65,6 +68,13 @@ module Rscons
       target.is_a?(Symbol)
     end
 
+    # Generate a random phony target name.
+    #
+    # @return [Symbol] Phony target name.
+    def gen_phony_target
+      ("t" + sprintf("%08x", rand(1_000_000..4_000_000_000))).to_sym
+    end
+
     # Return the system shell and arguments for executing a shell command.
     #
     # @return [Array<String>] The shell and flag.
@@ -135,25 +145,29 @@ require_relative "rscons/builders/mixins/object_deps"
 require_relative "rscons/builders/mixins/program"
 
 # default builders
-require_relative "rscons/builders/cfile"
+require_relative "rscons/builders/barrier"
 require_relative "rscons/builders/command"
 require_relative "rscons/builders/copy"
 require_relative "rscons/builders/directory"
 require_relative "rscons/builders/disassemble"
+require_relative "rscons/builders/lex"
 require_relative "rscons/builders/library"
 require_relative "rscons/builders/object"
+require_relative "rscons/builders/precompile"
 require_relative "rscons/builders/preprocess"
 require_relative "rscons/builders/program"
 require_relative "rscons/builders/shared_library"
 require_relative "rscons/builders/shared_object"
 require_relative "rscons/builders/simple_builder"
 require_relative "rscons/builders/size"
+require_relative "rscons/builders/yacc"
 
 # language support
 require_relative "rscons/builders/lang/asm"
 require_relative "rscons/builders/lang/c"
 require_relative "rscons/builders/lang/cxx"
 require_relative "rscons/builders/lang/d"
+require_relative "rscons/builders/lang/llvm_asm"
 
 # Unbuffer $stdout
 $stdout.sync = true

lib/rscons/application.rb

@@ -42,6 +42,16 @@ module Rscons
       @variant_groups = []
     end
 
+    # Return if Rscons is in the task execution phase.
+    #
+    # @api private
+    #
+    # @return [Boolean]
+    #   If Rscons is in the task execution phase.
+    def task_execution_phase?
+      @task_execution_phase
+    end
+
     # Run the application.
     #
     # Execute user-specified tasks.
@@ -54,13 +64,16 @@ module Rscons
     #   List of task(s) to execute.
     # @param show_tasks [Boolean]
     #   Flag to show tasks and exit.
+    # @param all_tasks [Boolean]
+    #   Flag to show all tasks (not just those with a description).
     # @param enabled_variants [String]
     #   User-specified variants list.
     #
     # @return [Integer]
     #   Process exit code (0 on success).
-    def run(rsconscript, tasks_and_params, show_tasks, enabled_variants)
+    def run(rsconscript, tasks_and_params, show_tasks, all_tasks, enabled_variants)
       Cache.instance["failed_commands"] = []
+      @tasks_and_params = tasks_and_params
       @enabled_variants = enabled_variants
       if enabled_variants == "" && !tasks_and_params.include?("configure")
         if cache_enabled_variants = Cache.instance["configuration_data"]["enabled_variants"]
@@ -68,13 +81,16 @@ module Rscons
         end
       end
       @script = Script.new
-      @script.load(rsconscript)
+      if should_load_script
+        @script.load(rsconscript)
+        enable_variants
+      end
       if show_tasks
-        show_script_tasks
+        show_script_tasks(all_tasks)
         return 0
       end
-      apply_task_params(tasks_and_params)
-      enable_variants
+      apply_task_params(false)
+      @task_execution_phase = true
       if tasks_and_params.empty?
         check_process_environments
         if Task.tasks["default"]
@@ -156,8 +172,8 @@ module Rscons
     def distclean
       cache = Cache.instance
       clean
-      FileUtils.rm_rf(@build_dir)
       cache.clear
+      FileUtils.rm_rf(@build_dir)
     end
 
     # Check if the project needs to be configured.
@@ -166,6 +182,7 @@ module Rscons
     #
     # @return [void]
     def check_configure
+      apply_task_params(true)
       enable_variants
       unless Cache.instance["configuration_data"]["configured"]
         if @script.autoconf
@@ -192,20 +209,20 @@ module Rscons
     #
     # @api private
     #
-    # @param options [Hash]
-    #   Options.
-    #
     # @return [void]
     def configure
-      co = ConfigureOp.new(@script)
-      begin
-        @script.configure(co)
-      rescue RsconsError => e
-        co.close(false)
-        raise e
+      unless @_configured
+        @_configured = true
+        co = ConfigureOp.new(@script)
+        begin
+          @script.configure(co)
+        rescue RsconsError => e
+          co.close(false)
+          raise e
+        end
+        Cache.instance["configuration_data"]["enabled_variants"] = @enabled_variants
+        co.close(true)
       end
-      Cache.instance["configuration_data"]["enabled_variants"] = @enabled_variants
-      co.close(true)
     end
 
     # Remove installed files.
@@ -220,7 +237,7 @@ module Rscons
       cache = Cache.instance
       cache.targets(true).each do |target|
         cache.remove_target(target)
-        next unless File.exists?(target)
+        next unless File.exist?(target)
         puts "Removing #{target}" if verbose
         FileUtils.rm_f(target)
       end
@@ -241,6 +258,14 @@ module Rscons
     #
     # @param name [String]
     #   Variant name.
+    # @param options [Hash]
+    #   Optional parameters.
+    # @option options [String] :default
+    #   Whether the variant is enabled by default (default: true).
+    # @option options [String] :key
+    #   Variant key, used to name an Environment's build directory. If nil,
+    #   this variant will not contribute to the Environment's build directory
+    #   name.
     def variant(name, options = {})
       if @active_variants
         !!@active_variants.find {|variant| variant[:name] == name}
@@ -277,6 +302,15 @@ module Rscons
     end
 
     # Create a variant group.
+    #
+    # @overload variant_group(name, options = {})
+    #   @param name [String]
+    #     Variant group name (optional).
+    #   @param options [Hash]
+    #     Optional variant group parameters.
+    # @overload variant_group(options = {})
+    #   @param options [Hash]
+    #     Optional variant group parameters.
     def variant_group(*args, &block)
       if args.first.is_a?(String)
         name = args.slice!(0)
@@ -340,10 +374,10 @@ module Rscons
       end
     end
 
-    def show_script_tasks
+    def show_script_tasks(all_tasks)
       puts "Tasks:"
       Task[].sort.each do |task_name, task|
-        if task.description
+        if task.description || all_tasks
           puts %[  #{sprintf("%-27s", task_name)} #{task.description}]
           task.params.each do |param_name, param|
             arg_text = "--#{param_name}"
@@ -354,20 +388,38 @@ module Rscons
           end
         end
       end
-    end
 
-    def apply_task_params(tasks_and_params)
-      tasks_and_params.each do |task_name, task_params|
-        task_params.each do |param_name, param_value|
-          if param = Task[task_name].params[param_name]
-            Task[task_name].set_param_value(param_name, param_value)
-          else
-            raise RsconsError.new("Unknown parameter #{param_name.inspect} for task #{task_name}")
+      unless @variant_groups.empty?
+        @variant_groups.each do |variant_group|
+          puts "\nVariant group#{variant_group[:name] ? " '#{variant_group[:name]}'" : ""}:"
+          variant_group[:variants].each do |variant|
+            puts "  #{variant[:name]}#{variant[:enabled] ? " (enabled)" : ""}"
           end
         end
       end
     end
 
+    def apply_task_params(only_configure)
+      @tasks_and_params.each do |task_name, task_params|
+        unless only_configure && task_name != "configure"
+          task_params.each do |param_name, param_value|
+            if param = Task[task_name].params[param_name]
+              Task[task_name].set_param_value(param_name, param_value)
+            else
+              raise RsconsError.new("Unknown parameter #{param_name.inspect} for task #{task_name}")
+            end
+          end
+        end
+      end
+    end
+
+    def should_load_script
+      return true if @tasks_and_params.empty?
+      return true if Cache.instance["configuration_data"]["configured"]
+      return false if (@tasks_and_params.keys - %w[distclean clean uninstall]).empty?
+      true
+    end
+
   end
 
 end

lib/rscons/builder_set.rb

@@ -27,8 +27,9 @@ module Rscons
       #   env.Directory("dest")
       #   env.Install("dest", "bin")
       #   env.Install("dest", "share")
-      self[builder.target] ||= []
-      self[builder.target] << builder
+      target = Util.absolute_path(builder.target)
+      self[target] ||= []
+      self[target] << builder
     end
 
     # Return the number of remaining build steps.
@@ -37,7 +38,7 @@ module Rscons
     #   The number of remaining build steps.
     def build_steps_remaining
       self.reduce(0) do |result, (target, builders)|
-        result + builders.size
+        result + builders.count {|b| !b.is_a?(Rscons::Builders::Barrier)}
       end
     end
 
@@ -55,9 +56,14 @@ module Rscons
     def get_next_builder_to_run(targets_still_building)
       to_build = self.find do |target, builders|
         deps = builders.first.sources + (@build_dependencies[target] || []).to_a
+        deps.map! {|dep| Util.absolute_path(dep)}
         # All dependencies must have been built for this target to be ready to
         # build.
         deps.all? do |dep|
+          puts "BuilderSet: #{target}: dep #{dep}"
+          puts "  still building? #{targets_still_building.include?(dep)}"
+          puts "  self.include? #{self.include?(dep)}"
+          puts "  @side_effects.include? #{@side_effects.include?(dep)}"
           !(targets_still_building.include?(dep) ||
             self.include?(dep) ||
             @side_effects.include?(dep))
@@ -66,6 +72,7 @@ module Rscons
 
       if to_build
         target, builders = *to_build
+        puts "Selecting #{target.inspect} to build"
         builder = builders.first
         if builders.size > 1
           builders.slice!(0)

lib/rscons/builders/barrier.rb

@@ -0,0 +1,15 @@
+module Rscons
+  module Builders
+    # The Barrier builder does not perform any action. It exists as a builder
+    # on which to place dependencies to ensure that each of its sources are
+    # built before any build targets which depend on the barrier build target.
+    class Barrier < Builder
+
+      # Run the builder.
+      def run(options)
+        true
+      end
+
+    end
+  end
+end

lib/rscons/builders/cfile.rb

@@ -1,35 +0,0 @@
-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
-
-      # Run the builder to produce a build target.
-      def run(options)
-        if @command
-          finalize_command
-        else
-          @vars["_TARGET"] = @target
-          @vars["_SOURCES"] = @sources
-          case
-          when @sources.first.end_with?(*@env.expand_varref("${LEXSUFFIX}"))
-            cmd = "LEX"
-            message = "Generating lexer"
-          when @sources.first.end_with?(*@env.expand_varref("${YACCSUFFIX}"))
-            cmd = "YACC"
-            message = "Generating parser"
-          else
-            raise "Unknown source file #{@sources.first.inspect} for CFile builder"
-          end
-          command = @env.build_command("${#{cmd}_CMD}", @vars)
-          standard_command("#{message} from <source>#{Util.short_format_paths(@sources)}<reset> => <target>#{@target}<reset>", command)
-        end
-      end
-
-    end
-  end
-end

lib/rscons/builders/copy.rb

@@ -14,14 +14,14 @@ module Rscons
       # Run the builder to produce a build target.
       def run(options)
         target_is_dir = (@sources.length > 1) ||
-                        Dir.exists?(@sources.first) ||
-                        Dir.exists?(@target)
+                        Dir.exist?(@sources.first) ||
+                        Dir.exist?(@target)
         outdir = target_is_dir ? @target : File.dirname(@target)
         # Collect the list of files to copy over.
         file_map = {}
         if target_is_dir
           @sources.each do |src|
-            if Dir.exists? src
+            if Dir.exist? src
               Dir.glob("#{src}/**/*", File::FNM_DOTMATCH).select do |f|
                 File.file?(f)
               end.each do |subfile|
@@ -50,7 +50,7 @@ module Rscons
           end
           @cache.register_build(dest, :Copy, [src], @env, install: @install_builder)
         end
-        (target_is_dir ? Dir.exists?(@target) : File.exists?(@target)) ? true : false
+        (target_is_dir ? Dir.exist?(@target) : File.exist?(@target)) ? true : false
       end
 
     end

lib/rscons/builders/directory.rb

@@ -14,7 +14,7 @@ module Rscons
       def run(options)
         if File.directory?(@target)
           true
-        elsif File.exists?(@target)
+        elsif File.exist?(@target)
           Ansi.write($stderr, :red, "Error: `#{@target}' already exists and is not a directory", :reset, "\n")
           false
         else

lib/rscons/builders/lang/llvm_asm.rb

@@ -0,0 +1,10 @@
+Rscons::Builders::Object.register(
+  command: "${LLVMAS_CMD}",
+  direct_command: "${LLVMAS_CMD:direct}",
+  suffix: "${LLVMAS_SUFFIX}",
+  short_description: "Assembling")
+Rscons::Builders::SharedObject.register(
+  command: "${LLVMAS_CMD}",
+  direct_command: "${LLVMAS_CMD:direct}",
+  suffix: "${LLVMAS_SUFFIX}",
+  short_description: "Assembling")

lib/rscons/builders/lex.rb

@@ -0,0 +1,24 @@
+module Rscons
+  module Builders
+    # Build a source file given a lex input file.
+    #
+    # Examples::
+    #   env.Lex("lex.c", "parser.l")
+    #   env.Lex("lex.cc", "parser.ll")
+    class Lex < Builder
+
+      # Run the builder to produce a build target.
+      def run(options)
+        if @command
+          finalize_command
+        else
+          @vars["_TARGET"] = @target
+          @vars["_SOURCES"] = @sources
+          command = @env.build_command("${LEX_CMD}", @vars)
+          standard_command("Generating lexer source from <source>#{Util.short_format_paths(@sources)}<reset> => <target>#{@target}<reset>", command)
+        end
+      end
+
+    end
+  end
+end

lib/rscons/builders/mixins/depfile.rb

@@ -8,7 +8,7 @@ module Rscons
         # dependency file.
         def finalize_command_with_depfile
           deps = @sources
-          if File.exists?(@vars["_DEPFILE"])
+          if File.exist?(@vars["_DEPFILE"])
             deps += Util.parse_dependency_file(@vars["_DEPFILE"])
           end
           @cache.register_build(@target, @command, deps.uniq, @env)

lib/rscons/builders/mixins/object_deps.rb

@@ -15,11 +15,16 @@ module Rscons
         #   List of paths to the object or static library dependencies.
         def register_object_deps(builder_class)
           suffixes = @env.expand_varref(["${OBJSUFFIX}", "${LIBSUFFIX}"], @vars)
+          barrier_target = @env.setup_precompile(@sources)
           @sources.map do |source|
             if source.end_with?(*suffixes)
               source
             else
-              @env.register_dependency_build(@target, source, suffixes.first, @vars, builder_class)
+              object_file_path = @env.register_dependency_build(@target, source, suffixes.first, @vars, builder_class)
+              if barrier_target
+                @env.depends(object_file_path, barrier_target)
+              end
+              object_file_path
             end
           end
         end

lib/rscons/builders/precompile.rb

@@ -0,0 +1,29 @@
+module Rscons
+  module Builders
+    # The Precompile builder generates .di interface files from .d source files
+    # for D.
+    class Precompile < Builder
+
+      # Run the builder to produce a build target.
+      def run(options)
+        if @command
+          finalize_command
+        else
+          if @sources.find {|s| s.end_with?(*@env.expand_varref("${DSUFFIX}", @vars))}
+            pcc = @env.expand_varref("${DC}")
+            if pcc =~ /ldc/
+              dpc_cmd = "${DPC_CMD:ldc}"
+            else
+              dpc_cmd = "${DPC_CMD:gdc}"
+            end
+            @vars["_TARGET"] = @target
+            @vars["_SOURCES"] = @sources
+            command = @env.build_command(dpc_cmd, @vars)
+            standard_command("Precompile <source>#{Util.short_format_paths(@sources)}<reset>", command)
+          end
+        end
+      end
+
+    end
+  end
+end

lib/rscons/builders/yacc.rb

@@ -0,0 +1,24 @@
+module Rscons
+  module Builders
+    # Build a source file given a yacc input file.
+    #
+    # Examples::
+    #   env.Yacc("parser.c", "parser.y")
+    #   env.Yacc("parser.cc", "parser.yy")
+    class Yacc < Builder
+
+      # Run the builder to produce a build target.
+      def run(options)
+        if @command
+          finalize_command
+        else
+          @vars["_TARGET"] = @target
+          @vars["_SOURCES"] = @sources
+          command = @env.build_command("${YACC_CMD}", @vars)
+          standard_command("Generating parser source from <source>#{Util.short_format_paths(@sources)}<reset> => <target>#{@target}<reset>", command)
+        end
+      end
+
+    end
+  end
+end

lib/rscons/cache.rb

@@ -101,6 +101,7 @@ module Rscons
     #
     # @return [void]
     def write
+      return unless Dir.exist?(File.dirname(cache_file))
       @cache["version"] = VERSION
       File.open(cache_file, "w") do |fh|
         fh.puts(JSON.dump(@cache))
@@ -141,14 +142,16 @@ module Rscons
     #   - each cached dependency file's current checksum matches the checksum
     #     stored in the cache file
     def up_to_date?(targets, command, deps, env, options = {})
+      deps.map! {|dep| Util.absolute_path(dep)}
       Array(targets).each do |target|
+        target = Util.absolute_path(target)
         cache_key = get_cache_key(target)
 
         unless Rscons.phony_target?(target)
           # target file must exist on disk
-          unless File.exists?(target)
-            if options[:debug]
-              puts "Target #{target} needs rebuilding because it does not exist on disk"
+          unless File.exist?(target)
+            if options[:debug] || ENV["RSCONS_CACHE_DEBUG"]
+              puts "Cache: up_to_date?: Target #{target} needs rebuilding because it does not exist on disk"
             end
             return false
           end
@@ -156,8 +159,8 @@ module Rscons
 
         # target must be registered in the cache
         unless @cache["targets"].has_key?(cache_key)
-          if options[:debug]
-            puts "Target #{target} needs rebuilding because there is no cached build information for it"
+          if options[:debug] || ENV["RSCONS_CACHE_DEBUG"]
+            puts "Cache: up_to_date?: Target #{target} needs rebuilding because there is no cached build information for it"
           end
           return false
         end
@@ -165,8 +168,8 @@ module Rscons
         unless Rscons.phony_target?(target)
           # target must have the same checksum as when it was built last
           unless @cache["targets"][cache_key]["checksum"] == lookup_checksum(target)
-            if options[:debug]
-              puts "Target #{target} needs rebuilding because it has been changed on disk since being built last"
+            if options[:debug] || ENV["RSCONS_CACHE_DEBUG"]
+              puts "Cache: up_to_date?: Target #{target} needs rebuilding because it has been changed on disk since being built last"
             end
             return false
           end
@@ -174,8 +177,8 @@ module Rscons
 
         # command used to build target must be identical
         unless @cache["targets"][cache_key]["command"] == Digest::MD5.hexdigest(command.inspect)
-          if options[:debug]
-            puts "Target #{target} needs rebuilding because the command used to build it has changed"
+          if options[:debug] || ENV["RSCONS_CACHE_DEBUG"]
+            puts "Cache: up_to_date?: Target #{target} needs rebuilding because the command used to build it has changed"
           end
           return false
         end
@@ -185,16 +188,16 @@ module Rscons
         if options[:strict_deps]
           # depedencies passed in must exactly equal those in the cache
           unless deps == cached_deps_fnames
-            if options[:debug]
-              puts "Target #{target} needs rebuilding because the :strict_deps option is given and the set of dependencies does not match the previous set of dependencies"
+            if options[:debug] || ENV["RSCONS_CACHE_DEBUG"]
+              puts "Cache: up_to_date?: Target #{target} needs rebuilding because the :strict_deps option is given and the set of dependencies does not match the previous set of dependencies"
             end
             return false
           end
         else
           # all dependencies passed in must exist in cache (but cache may have more)
           unless (Set.new(deps) - Set.new(cached_deps_fnames)).empty?
-            if options[:debug]
-              puts "Target #{target} needs rebuilding because there are new dependencies"
+            if options[:debug] || ENV["RSCONS_CACHE_DEBUG"]
+              puts "Cache: up_to_date?: Target #{target} needs rebuilding because there are new dependencies"
             end
             return false
           end
@@ -202,11 +205,12 @@ module Rscons
 
         # set of user dependencies must match
         user_deps = env.get_user_deps(target) || []
+        user_deps.map! {|dep| Util.absolute_path(dep)}
         cached_user_deps = @cache["targets"][cache_key]["user_deps"] || []
         cached_user_deps_fnames = cached_user_deps.map { |dc| dc["fname"] }
         unless user_deps == cached_user_deps_fnames
-          if options[:debug]
-            puts "Target #{target} needs rebuilding because the set of user-specified dependency files has changed"
+          if options[:debug] || ENV["RSCONS_CACHE_DEBUG"]
+            puts "Cache: up_to_date?: Target #{target} needs rebuilding because the set of user-specified dependency files has changed"
           end
           return false
         end
@@ -214,12 +218,14 @@ module Rscons
         # all cached dependencies must have their checksums match
         (cached_deps + cached_user_deps).each do |dep_cache|
           unless dep_cache["checksum"] == lookup_checksum(dep_cache["fname"])
-            if options[:debug]
-              puts "Target #{target} needs rebuilding because dependency file #{dep_cache["fname"]} has changed"
+            if options[:debug] || ENV["RSCONS_CACHE_DEBUG"]
+              puts "Cache: up_to_date?: Target #{target} needs rebuilding because dependency file #{dep_cache["fname"]} has changed"
             end
             return false
           end
         end
+
+        puts "Cache: up_to_date?: Target #{target} is up to date" if ENV["RSCONS_CACHE_DEBUG"]
       end
 
       true
@@ -246,22 +252,26 @@ module Rscons
     # @return [void]
     def register_build(targets, command, deps, env, options = {})
       Array(targets).each do |target|
+        target = Util.absolute_path(target)
         target_checksum =
           if options[:side_effect] or Rscons.phony_target?(target)
             ""
           else
             calculate_checksum(target)
           end
+        puts "Cache: register_build(#{target}, #{target_checksum})"
         @cache["targets"][get_cache_key(target)] = {
           "command" => Digest::MD5.hexdigest(command.inspect),
           "checksum" => target_checksum,
           "deps" => deps.map do |dep|
+            dep = Util.absolute_path(dep)
             {
               "fname" => dep,
               "checksum" => lookup_checksum(dep),
             }
           end,
           "user_deps" => (env.get_user_deps(target) || []).map do |dep|
+            dep = Util.absolute_path(dep)
             {
               "fname" => dep,
               "checksum" => lookup_checksum(dep),
@@ -306,7 +316,7 @@ module Rscons
       parts.each_index do |i|
         next if parts[i] == ""
         subpath = File.join(*parts[0, i + 1])
-        unless File.exists?(subpath)
+        unless File.exist?(subpath)
           FileUtils.mkdir_p(subpath)
           @cache["directories"][subpath] = !!options[:install]
         end
@@ -380,6 +390,8 @@ module Rscons
     #
     # @return [String] The file's checksum.
     def lookup_checksum(file)
+      file = Util.absolute_path(file)
+      puts "Cache: lookup_checksum(#{file})" if ENV["RSCONS_CACHE_DEBUG"]
       @lookup_checksums[file] || calculate_checksum(file)
     end
 
@@ -389,7 +401,10 @@ module Rscons
     #
     # @return [String] The file's checksum.
     def calculate_checksum(file)
-      @lookup_checksums[file] = Digest::MD5.hexdigest(File.read(file, mode: "rb")) rescue ""
+      file = Util.absolute_path(file)
+      cs = Digest::MD5.hexdigest(File.read(file, mode: "rb")) rescue ""
+      puts "Cache: calculate_checksum(#{file}) = #{cs}" if ENV["RSCONS_CACHE_DEBUG"]
+      @lookup_checksums[file] = cs
     end
 
   end

lib/rscons/cli.rb

@@ -54,10 +54,15 @@ module Rscons
     def run_toplevel(argv)
       rsconscript = nil
       show_tasks = false
+      all_tasks = false
       enabled_variants = ""
 
       OptionParser.new do |opts|
 
+        opts.on("-A", "--all") do
+          all_tasks = true
+        end
+
         opts.on("-b", "--build DIR") do |build_dir|
           Rscons.application.build_dir = build_dir
         end
@@ -113,13 +118,13 @@ module Rscons
 
       # Find the build script.
       if rsconscript
-        unless File.exists?(rsconscript)
+        unless File.exist?(rsconscript)
           $stderr.puts "Cannot read #{rsconscript}"
           return 1
         end
       else
         rsconscript = DEFAULT_RSCONSCRIPTS.find do |f|
-          File.exists?(f)
+          File.exist?(f)
         end
       end
 
@@ -132,7 +137,7 @@ module Rscons
       end
 
       begin
-        Rscons.application.run(rsconscript, tasks_and_params, show_tasks, enabled_variants)
+        Rscons.application.run(rsconscript, tasks_and_params, show_tasks, all_tasks, enabled_variants)
       rescue RsconsError => e
         Ansi.write($stderr, :red, e.message, :reset, "\n")
         1
@@ -144,16 +149,49 @@ module Rscons
 Usage: #{$0} [global options] [[task] [task options] ...]
 
 Global options:
-  -b BUILD, --build=BUILD     Set build directory (default: build)
-  -e VS, --variants=VS        Enable or disable variants
-  -f FILE                     Use FILE as Rsconscript
-  -F, --show-failure          Show failed command log from previous build and exit
-  -h, --help                  Show rscons help and exit
-  -j N, --nthreads=N          Set number of threads (local default: #{Rscons.application.n_threads})
-  -r COLOR, --color=COLOR     Set color mode (off, auto, force)
-  -T, --tasks                 Show task list and parameters and exit
-  -v, --verbose               Run verbosely
-  --version                   Show rscons version and exit
+  -A, --all
+    Show all tasks (even those without descriptions) in task list. Use in
+    conjunction with the -T argument.
+
+  -b BUILD, --build=BUILD
+    Set build directory (default: build).
+
+  -e VS, --variants=VS
+    Enable or disable variants. VS is a comma-separated list of variant
+    entries. If the entry begins with "-" the variant is disabled instead of
+    enabled. If the full list begins with "+" or "-" then it modifies the
+    variants that are enabled by default by only enabling or disabling the
+    listed variants. Otherwise, the enabled set of variants is as given and
+    any variants not listed are disabled. The set of enabled variants is
+    remembered from when the project is configured.
+
+  -f FILE
+    Use FILE as Rsconscript.
+
+  -F, --show-failure
+    Show failed command log from previous build and exit (does not load build
+    script).
+
+  -h, --help
+    Show rscons help and exit (does not load build script).
+
+  -j N, --nthreads=N
+    Set number of threads (local default: #{Rscons.application.n_threads}).
+
+  -r COLOR, --color=COLOR
+    Set color mode (off, auto, force).
+
+  -T, --tasks
+    Show task list and parameters and exit (loads build script). By default
+    only tasks with a description are listed. Use -AT to show all tasks whether
+    they have a description or not.
+
+  -v, --verbose
+    Run verbosely. This causes Rscons to print the full build command used by
+    each builder.
+
+  --version
+    Show rscons version and exit (does not load build script).
 EOF
     end
 

lib/rscons/configure_op.rb

@@ -1,5 +1,6 @@
 require "fileutils"
 require "open3"
+require "set"
 
 module Rscons
   # Class to manage a configure operation.
@@ -10,9 +11,11 @@ module Rscons
     # @param script [Script]
     #   Build script.
     def initialize(script)
+      @tested_compilers = {}
       @work_dir = "#{Rscons.application.build_dir}/_configure"
       FileUtils.mkdir_p(@work_dir)
-      @log_fh = File.open("#{@work_dir}/config.log", "wb")
+      @log_file_name = "#{@work_dir}/config.log"
+      @log_fh = File.open(@log_file_name, "wb")
       cache = Cache.instance
       cache["failed_commands"] = []
       cache["configuration_data"] = {}
@@ -23,14 +26,11 @@ module Rscons
           $stdout.puts "Configuring project..."
         end
       end
-      vars = {}
       Task["configure"].params.each do |name, param|
         unless Rscons.application.silent_configure
           Ansi.write($stdout, "Setting #{name}... ", :green, param.value, :reset, "\n")
         end
-        vars[name] = param.value
       end
-      store_merge(vars)
     end
 
     # Close the log file handle.
@@ -65,9 +65,15 @@ module Rscons
         ccc = %w[gcc clang]
       end
       cc = ccc.find do |cc|
-        test_c_compiler(cc)
+        test_c_compiler(cc, options)
       end
-      complete(cc ? 0 : 1, options.merge(success_message: cc))
+      if cc
+        @tested_compilers["c"] ||= Set.new
+        @tested_compilers["c"] << cc
+      end
+      complete(cc ? 0 : 1, options.merge(
+        success_message: cc,
+        fail_message: "not found (checked #{ccc.join(", ")})"))
     end
 
     # Check for a working C++ compiler.
@@ -87,9 +93,15 @@ module Rscons
         ccc = %w[g++ clang++]
       end
       cc = ccc.find do |cc|
-        test_cxx_compiler(cc)
+        test_cxx_compiler(cc, options)
       end
-      complete(cc ? 0 : 1, options.merge(success_message: cc))
+      if cc
+        @tested_compilers["cxx"] ||= Set.new
+        @tested_compilers["cxx"] << cc
+      end
+      complete(cc ? 0 : 1, options.merge(
+        success_message: cc,
+        fail_message: "not found (checked #{ccc.join(", ")})"))
     end
 
     # Check for a working D compiler.
@@ -106,12 +118,18 @@ module Rscons
       end
       if cdc.empty?
         # Default D compiler search array.
-        cdc = %w[gdc ldc2]
+        cdc = %w[gdc ldc2 ldc]
       end
       dc = cdc.find do |dc|
-        test_d_compiler(dc)
+        test_d_compiler(dc, options)
       end
-      complete(dc ? 0 : 1, options.merge(success_message: dc))
+      if dc
+        @tested_compilers["d"] ||= Set.new
+        @tested_compilers["d"] << dc
+      end
+      complete(dc ? 0 : 1, options.merge(
+        success_message: dc,
+        fail_message: "not found (checked #{cdc.join(", ")})"))
     end
 
     # Check for a package or configure program output.
@@ -121,7 +139,12 @@ module Rscons
       elsif program = options[:program]
         Ansi.write($stdout, "Checking '", :cyan, program, :reset, "'... ")
       end
-      program ||= "pkg-config"
+      unless program
+        program = "pkg-config"
+        unless Util.find_executable(program)
+          raise RsconsError.new("Error: executable '#{program}' not found")
+        end
+      end
       args = options[:args] || %w[--cflags --libs]
       command = [program, *args, package].compact
       stdout, _, status = log_and_test_command(command)
@@ -243,17 +266,36 @@ module Rscons
     def check_lib(lib, options = {})
       check_libpath = [nil] + (options[:check_libpath] || [])
       Ansi.write($stdout, "Checking for library '", :cyan, lib, :reset, "'... ")
-      File.open("#{@work_dir}/cfgtest.c", "wb") do |fh|
-        fh.puts <<-EOF
-          int main(int argc, char * argv[]) {
-            return 0;
-          }
-        EOF
+      if @tested_compilers["d"]
+        source_file = "#{@work_dir}/cfgtest.d"
+        File.open(source_file, "wb") do |fh|
+          fh.puts <<-EOF
+            int main() {
+              return 0;
+            }
+          EOF
+        end
+      else
+        source_file = "#{@work_dir}/cfgtest.c"
+        File.open(source_file, "wb") do |fh|
+          fh.puts <<-EOF
+            int main(int argc, char * argv[]) {
+              return 0;
+            }
+          EOF
+        end
+      end
+      ld = "${CC}"
+      %w[d cxx c].each do |language|
+        if @tested_compilers[language]
+          ld = @tested_compilers[language].first
+          break
+        end
       end
       vars = {
-        "LD" => "${CC}",
+        "LD" => ld,
         "LIBS" => [lib],
-        "_SOURCES" => "#{@work_dir}/cfgtest.c",
+        "_SOURCES" => source_file,
         "_TARGET" => "#{@work_dir}/cfgtest.exe",
       }
       status = 1
@@ -378,6 +420,8 @@ module Rscons
     #   A define to set (in CPPDEFINES) if the requested item is found.
     # @option options [String] :success_message
     #   Message to print on success (default "found").
+    # @option options [String] :fail_message
+    #   Message to print on failure (default "not found").
     def complete(status, options)
       success_message = options[:success_message] || "found"
       fail_message = options[:fail_message] || "not found"
@@ -401,7 +445,7 @@ module Rscons
           options[:on_fail].call
         end
         if should_fail
-          raise RsconsError.new("Configuration failed")
+          raise RsconsError.new("Configuration failed; log file written to #{@log_file_name}")
         end
       end
     end
@@ -415,7 +459,7 @@ module Rscons
     #
     # @return [Boolean]
     #   Whether the C compiler tested successfully.
-    def test_c_compiler(cc)
+    def test_c_compiler(cc, options)
       File.open("#{@work_dir}/cfgtest.c", "wb") do |fh|
         fh.puts <<-EOF
           int fun(int val) {
@@ -427,7 +471,7 @@ module Rscons
       merge = {"CC" => cc}
       _, _, status = log_and_test_command(command)
       if status == 0
-        store_merge(merge)
+        store_merge(merge, options)
         true
       end
     end
@@ -439,7 +483,7 @@ module Rscons
     #
     # @return [Boolean]
     #   Whether the C++ compiler tested successfully.
-    def test_cxx_compiler(cc)
+    def test_cxx_compiler(cc, options)
       File.open("#{@work_dir}/cfgtest.cxx", "wb") do |fh|
         fh.puts <<-EOF
           template<typename T>
@@ -452,7 +496,7 @@ module Rscons
       merge = {"CXX" => cc}
       _, _, status = log_and_test_command(command)
       if status == 0
-        store_merge(merge)
+        store_merge(merge, options)
         true
       end
     end
@@ -464,7 +508,7 @@ module Rscons
     #
     # @return [Boolean]
     #   Whether the D compiler tested successfully.
-    def test_d_compiler(dc)
+    def test_d_compiler(dc, options)
       File.open("#{@work_dir}/cfgtest.d", "wb") do |fh|
         fh.puts <<-EOF
           import core.math;
@@ -485,15 +529,17 @@ module Rscons
           env = BasicEnvironment.new
           merge = {
             "DC" => dc,
-            "DCCMD" => env["DCCMD"].map {|e| e.sub(/^-o$/, "-of")},
-            "LDCMD" => env["LDCMD"].map {|e| e.sub(/^-o$/, "-of")},
+            "DC:-o" => "-of",
+            "LD:-o" => "-of",
+            "LIBDIRPREFIX" => "-L-L",
+            "LIBLINKPREFIX" => "-L-l",
             "DDEPGEN" => ["-deps=${_DEPFILE}"],
           }
           merge["OBJSUFFIX"] = [ldc_objsuffix]
         end
         _, _, status = log_and_test_command(command)
         if status == 0
-          store_merge(merge)
+          store_merge(merge, options)
           true
         end
       end

lib/rscons/default_construction_variables.rb

@@ -35,21 +35,24 @@ module Rscons
     "CXXFLAGS" => [],
     "CXXSUFFIX" => %w[.cc .cpp .cxx .C],
     "DC" => "gdc",
-    "DCCMD" => %w[${DC} -c -o ${_TARGET} ${DDEPGEN} ${INCPREFIX}${D_IMPORT_PATH} ${DFLAGS} ${_SOURCES}],
-    "DCCMD:direct" => %w[${DC} -o ${_TARGET} ${DDEPGEN} ${INCPREFIX}${D_IMPORT_PATH} ${DFLAGS} ${LDFLAGS} ${_SOURCES} ${LIBDIRPREFIX}${LIBPATH} ${LIBLINKPREFIX}${LIBS}],
+    "DC:-o" => "-o",
+    "DCCMD" => %w[${DC} -c ${DC:-o} ${_TARGET} ${DDEPGEN} ${INCPREFIX}${D_IMPORT_PATH} ${DFLAGS} ${_SOURCES}],
+    "DCCMD:direct" => %w[${DC} ${DC:-o} ${_TARGET} ${DDEPGEN} ${INCPREFIX}${D_IMPORT_PATH} ${DFLAGS} ${LDFLAGS} ${_SOURCES} ${LIBDIRPREFIX}${LIBPATH} ${LIBLINKPREFIX}${LIBS}],
     "DDEPGEN" => %w[-MMD -MF ${_DEPFILE}],
     "DEPFILESUFFIX" => ".mf",
     "DFLAGS" => [],
     "DISASM_CMD" => %w[${OBJDUMP} ${DISASM_FLAGS} ${_SOURCES}],
     "DISASM_FLAGS" => %w[--disassemble --source],
+    "DPC_CMD:ldc" => %w[${DC} -H -Hf ${_TARGET} -o- ${INCPREFIX}${D_IMPORT_PATH} ${DFLAGS} ${_SOURCES}],
+    "DPC_CMD:gdc" => %w[${DC} -H -Hf ${_TARGET} -fsyntax-only ${INCPREFIX}${D_IMPORT_PATH} ${DFLAGS} ${_SOURCES}],
     "DSUFFIX" => %w[.d],
     "D_IMPORT_PATH" => [],
     "INCPREFIX" => "-I",
     "LD" => nil,
-    "LDCMD" => %w[${LD} -o ${_TARGET} ${LDFLAGS} ${_SOURCES} ${LIBDIRPREFIX}${LIBPATH} ${LIBLINKPREFIX}${LIBS}],
+    "LD:-o" => "-o",
+    "LDCMD" => %w[${LD} ${LD:-o} ${_TARGET} ${LDFLAGS} ${_SOURCES} ${LIBDIRPREFIX}${LIBPATH} ${LIBLINKPREFIX}${LIBS}],
     "LDFLAGS" => [],
     "LEX" => "flex",
-    "LEXSUFFIX" => %w[.l .ll],
     "LEX_CMD" => %w[${LEX} ${LEX_FLAGS} -o ${_TARGET} ${_SOURCES}],
     "LEX_FLAGS" => [],
     "LIBDIRPREFIX" => "-L",
@@ -57,6 +60,11 @@ module Rscons
     "LIBPATH" => [],
     "LIBS" => [],
     "LIBSUFFIX" => ".a",
+    "LLVMAS" => "clang",
+    "LLVMAS_CMD" => %w[${LLVMAS} -c -o ${_TARGET} ${LLVMAS_FLAGS} ${_SOURCES}],
+    "LLVMAS_CMD:direct" => %w[${LLVMAS} -o ${_TARGET} ${LLVMAS_FLAGS} ${LDFLAGS} ${_SOURCES} ${LIBDIRPREFIX}${LIBPATH} ${LIBLINKPREFIX}${LIBS}],
+    "LLVMAS_FLAGS" => [],
+    "LLVMAS_SUFFIX" => ".ll",
     "OBJDUMP" => "objdump",
     "OBJSUFFIX" => %w[.o],
     "PROGSUFFIX" => on_windows ? ".exe" : "",
@@ -84,7 +92,6 @@ module Rscons
     "SIZECMD" => %w[${SIZE} ${SIZEFLAGS} ${_SOURCES}],
     "SIZEFLAGS" => [],
     "YACC" => "bison",
-    "YACCSUFFIX" => %w[.y .yy],
     "YACC_CMD" => %w[${YACC} ${YACC_FLAGS} -o ${_TARGET} ${_SOURCES}],
     "YACC_FLAGS" => %w[-d],
   }

lib/rscons/environment.rb

@@ -72,35 +72,21 @@ module Rscons
     attr_reader :name
 
     # Create an Environment object.
-    #
-    # @overload initialize(name, options)
-    # @overload initialize(options)
-    #
-    # @param name [String]
-    #   Environment name. This determines the folder name used to store all
-    #   environment build files under the top-level build directory.
-    # @param options [Hash]
-    # @option options [Symbol] :echo
-    #   :command, :short, or :off (default :short)
-    # @option options [Boolean] :exclude_builders
-    #   Whether to omit adding default builders (default false)
-    # @option options [String, Array<String>] :use
-    #   Use flag(s). If specified, any configuration flags which were saved
-    #   with a corresponding `:use` value will be applied to this Environment.
-    #
-    # If a block is given, the Environment object is yielded to the block and
-    # when the block returns, the {#process} method is automatically called.
     def initialize(*args, &block)
       @id = self.class.get_id
-      if args.first.is_a?(String)
-        base_name = args.slice!(0)
-      else
-        base_name = "e.#{@id}"
-      end
       variant_keys = (Rscons.application.active_variants || []).map do |variant|
         variant[:key]
       end.compact
-      @name = [base_name, *variant_keys].join("-")
+      if args.first.is_a?(String)
+        base_name = args.slice!(0)
+        @name = [base_name, *variant_keys].join("-")
+        @build_root = "#{Rscons.application.build_dir}/#{@name}"
+      else
+        if variant_keys.size > 0
+          raise RsconsError.new("Error: an Environment with active variants must be given a name")
+        end
+        @build_root = Rscons.application.build_dir
+      end
       options = args.first || {}
       unless Cache.instance["configuration_data"]["configured"]
         raise "Project must be configured before creating an Environment"
@@ -132,8 +118,8 @@ module Rscons
         else
           :short
         end
-      @build_root = "#{Rscons.application.build_dir}/#{@name}"
       @n_threads = Rscons.application.n_threads
+      @build_steps = 0
       self.class.register(self)
       if block
         Environment.running_environment = self
@@ -294,7 +280,26 @@ module Rscons
       if extra_path = builder_class.extra_path
         extra_path = "/#{extra_path}"
       end
-      "#{@build_root}#{extra_path}/#{Util.make_relative_path("#{source_fname}#{suffix}")}".gsub("\\", "/")
+      source_fname = source_fname.gsub("\\", "/")
+      if extra_path.nil? && source_fname.start_with?("#{@build_root}/")
+        # If the source file is in the environment's build directory and no
+        # builder "extra path" is present, then just place the output file
+        # next to the source file.
+        "#{source_fname}#{suffix}"
+      else
+        "#{@build_root}/o#{extra_path}/#{Util.make_relative_path("#{source_fname}#{suffix}")}"
+      end
+    end
+
+    # Get a path under the build root for precompile outputs.
+    #
+    # @param end_path [String]
+    #   Path to append to precompile build root.
+    #
+    # @return [String]
+    #   Precompile directory name.
+    def get_pc_build_dir(end_path)
+      "#{@build_root}/pc/#{Util.make_relative_path(end_path)}"
     end
 
     # Build all build targets specified in the Environment.
@@ -377,6 +382,7 @@ module Rscons
           @builder_sets << build_builder_set
         end
         @builder_sets.last << builder
+        @build_steps += 1
         @build_targets[target] = builder
         builder
       else
@@ -394,7 +400,9 @@ module Rscons
       if target.is_a?(Builder)
         target = target.target
       end
-      target = expand(target.to_s)
+      unless Rscons.phony_target?(target)
+        target = Util.absolute_path(expand(target))
+      end
       user_deps = user_deps.map do |ud|
         if ud.is_a?(Builder)
           ud = ud.target
@@ -402,7 +410,11 @@ module Rscons
         expand(ud)
       end
       @user_deps[target] ||= []
-      @user_deps[target] = (@user_deps[target] + user_deps).uniq
+      user_deps.each do |ud|
+        unless @user_deps[target].include?(ud)
+          @user_deps[target] << Util.absolute_path(ud)
+        end
+      end
       build_after(target, user_deps)
     end
 
@@ -433,14 +445,16 @@ module Rscons
       targets = Array(targets)
       prerequisites = Array(prerequisites)
       targets.each do |target|
-        target = expand(target)
+        unless Rscons.phony_target?(target)
+          target = Util.absolute_path(expand(target))
+        end
         @registered_build_dependencies[target] ||= Set.new
         prerequisites.each do |prerequisite|
           if prerequisite.is_a?(Builder)
             prerequisite = prerequisite.target
           end
           prerequisite = expand(prerequisite)
-          @registered_build_dependencies[target] << prerequisite
+          @registered_build_dependencies[target] << Util.absolute_path(prerequisite)
         end
       end
     end
@@ -455,7 +469,7 @@ module Rscons
     #
     # @return [void]
     def produces(target, *side_effects)
-      target = expand(target)
+      target = Util.absolute_path(expand(target))
       @builder_sets.reverse.each do |builder_set|
         if builders = builder_set[target]
           builders.last.produces(*side_effects)
@@ -601,6 +615,42 @@ module Rscons
       @builder_sets << build_builder_set
     end
 
+    # Set up builders and barrier for a precompile phase if needed.
+    #
+    # @param sources [Array<String>]
+    #   Sources for the build operation.
+    #
+    # @return [Symbol, nil]
+    #   Barrier target name if a precompile phase is needed, otherwise nil.
+    def setup_precompile(sources)
+      barrier_target = nil
+      precompile_paths = Set.new
+      sources.each do |source|
+        next unless source.end_with?(".d")
+        unless barrier_target
+          barrier_target = Rscons.gen_phony_target
+          self.Barrier(barrier_target)
+        end
+        next unless module_name = Util.get_module_name(source)
+        next unless import_path = Util.find_import_path_for_d_source(self["D_IMPORT_PATH"], source, module_name)
+        precompile_path = get_pc_build_dir(import_path)
+        unless precompile_paths.include?(precompile_path)
+          Util.clean_d_precompile_path(precompile_path, import_path)
+          precompile_paths << precompile_path
+        end
+        unless self["D_IMPORT_PATH"].include?(precompile_path)
+          # Put the precompile path containing the .di files for the given
+          # import path immediately before the import path.
+          index = self["D_IMPORT_PATH"].find_index {|ip| ip == import_path}
+          self["D_IMPORT_PATH"].insert(index, precompile_path)
+        end
+        pctarget = "#{precompile_path}/#{module_name.gsub(".", "/")}.di"
+        self.Precompile(pctarget, source)
+        self.depends(barrier_target, pctarget)
+      end
+      barrier_target
+    end
+
     private
 
     # Build a BuilderSet.
@@ -628,7 +678,9 @@ module Rscons
     #
     # @return [void]
     def run_builder(builder)
-      builder.build_step ||= get_next_build_step
+      unless builder.is_a?(Rscons::Builders::Barrier)
+        builder.build_step ||= get_next_build_step
+      end
       case result = builder.run({})
       when Array
         result.each do |waititem|
@@ -654,8 +706,10 @@ module Rscons
           Cache.instance.register_build(side_effect, nil, [], self, side_effect: true)
           @side_effects.delete(side_effect)
         end
-        @build_hooks[:post].each do |build_hook_block|
-          build_hook_block.call(builder)
+        unless builder.is_a?(Rscons::Builders::Barrier)
+          @build_hooks[:post].each do |build_hook_block|
+            build_hook_block.call(builder)
+          end
         end
         process_remove_wait(builder)
       else
@@ -727,13 +781,15 @@ module Rscons
       # If no builder was found to run yet and there are threads available, try
       # to get a runnable builder from the builder set.
       targets_still_building = @threads.reduce([]) do |result, (thread, obj)|
-        result << builder_for_thread(thread).target
+        result << Util.absolute_path(builder_for_thread(thread).target)
       end
       if @builder_sets.size > 0
         if builder = @builder_sets[0].get_next_builder_to_run(targets_still_building)
           builder.vars = @varset.merge(builder.vars)
-          @build_hooks[:pre].each do |build_hook_block|
-            build_hook_block.call(builder)
+          unless builder.is_a?(Rscons::Builders::Barrier)
+            @build_hooks[:pre].each do |build_hook_block|
+              build_hook_block.call(builder)
+            end
           end
           return run_builder(builder)
         end

lib/rscons/script.rb

@@ -10,6 +10,14 @@ module Rscons
         @script = script
       end
 
+      # Get the Rscons build directory path.
+      #
+      # @return [String]
+      #   Rscons build directory path.
+      def build_dir
+        Rscons.application.build_dir
+      end
+
       # Return a list of paths matching the specified pattern(s).
       #
       # A pattern can contain a "/**" component to recurse through directories.
@@ -26,15 +34,7 @@ module Rscons
       #
       # @return [Array<String>] Paths matching the specified pattern(s).
       def glob(*patterns)
-        require "pathname"
-        patterns.reduce([]) do |result, pattern|
-          if pattern.end_with?("/**")
-            pattern += "/"
-          end
-          result += Dir.glob(pattern).map do |path|
-            Pathname.new(path.gsub("\\", "/")).cleanpath.to_s
-          end
-        end.sort
+        Util.glob(*patterns)
       end
 
       # Download a file.
@@ -94,9 +94,49 @@ module Rscons
       end
 
       # Create an environment.
+      #
+      # @overload env(name, options)
+      #   @param name [String]
+      #     Environment name. This determines the folder name used to store all
+      #     environment build files under the top-level build directory.
+      #   @param options [Hash]
+      #   @option options [Symbol] :echo
+      #     :command, :short, or :off (default :short)
+      #   @option options [Boolean] :exclude_builders
+      #     Whether to omit adding default builders (default false)
+      #   @option options [String, Array<String>] :use
+      #     Use flag(s). If specified, any configuration flags which were saved
+      #     with a corresponding `:use` value will be applied to this
+      #     Environment.
+      #
+      # @overload env(options)
+      #   @param options [Hash]
+      #   @option options [Symbol] :echo
+      #     :command, :short, or :off (default :short)
+      #   @option options [Boolean] :exclude_builders
+      #     Whether to omit adding default builders (default false)
+      #   @option options [String, Array<String>] :use
+      #     Use flag(s). If specified, any configuration flags which were saved
+      #     with a corresponding `:use` value will be applied to this
+      #     Environment.
+      #
+      # If a block is given it is immediately executed and passed the newly
+      # created Environment object as an argument.
+      # If the Environment is created in task context, the +process+ method is
+      # immediately called.
+      # Otherwise, the Environment is not processed until the task execution
+      # phase.
+      #
+      # @yield [env]
+      # @yieldparam env [Environment]
+      #   The created environment.
       def env(*args, &block)
         Rscons.application.check_configure
-        Environment.new(*args, &block)
+        e = Environment.new(*args, &block)
+        if Rscons.application.task_execution_phase?
+          e.process
+        end
+        e
       end
 
       # Construct a task parameter.
@@ -241,27 +281,80 @@ module Rscons
       end
 
       # Create or modify a task.
+      #
+      # @overload task(name, options = {}, &block)
+      #   @param name [String]
+      #     Task name.
+      #   @param options [Hash]
+      #     Optional task attributes.
+      #   @option options [Boolean] :autoconf
+      #     Whether to automatically configure before running this task
+      #     (default: true).
+      #   @option options [String] :desc
+      #     Description for the task.
+      #   @option options [Array<String>] :depends
+      #     Dependencies of the task.
+      #   @option options [Array<Task::Param>] :params
+      #     Task parameter definitions.
+      #
+      # The action block given will be invoked by Rscons when the task
+      # executes. It will be passed two arguments:
+      #   1) The Task object.
+      #   2) A Hash of task parameter names and values.
       def task(*args, &block)
         Util.task(*args, &block)
       end
 
       # Define a variant, or within a with_variants block, query if it is
       # active.
-      def variant(*args)
-        Rscons.application.variant(*args)
+      #
+      # @param name [String]
+      #   Variant name.
+      # @param options [Hash]
+      #   Optional parameters.
+      # @option options [String] :default
+      #   Whether the variant is enabled by default (default: true).
+      # @option options [String] :key
+      #   Variant key, used to name an Environment's build directory. If nil,
+      #   this variant will not contribute to the Environment's build directory
+      #   name.
+      def variant(name, options = {})
+        Rscons.application.variant(name, options)
       end
 
       # Check if a variant is enabled.
-      def variant_enabled?(*args)
-        Rscons.application.variant_enabled?(*args)
+      #
+      # This can be used, for example, in a configuration block to omit or
+      # include configuration checks based on which variants have been
+      # configured.
+      #
+      # @param variant_name [String]
+      #   Variant name.
+      #
+      # @return [Boolean]
+      #   Whether the requested variant is enabled.
+      def variant_enabled?(variant_name)
+        Rscons.application.variant_enabled?(variant_name)
       end
 
       # Create a variant group.
+      #
+      # @overload variant_group(name, options = {})
+      #   @param name [String]
+      #     Variant group name (optional).
+      #   @param options [Hash]
+      #     Optional variant group parameters.
+      # @overload variant_group(options = {})
+      #   @param options [Hash]
+      #     Optional variant group parameters.
       def variant_group(*args, &block)
         Rscons.application.variant_group(*args, &block)
       end
 
-      # Iterate through variants.
+      # Iterate through enabled variants.
+      #
+      # The given block is called for each combination of enabled variants
+      # across the defined variant groups.
       def with_variants(&block)
         Rscons.application.enable_variants
         Rscons.application.with_variants(&block)
@@ -301,11 +394,17 @@ module Rscons
     # Top-level DSL available to the Rsconscript.
     class TopLevelDsl < GlobalDsl
       # Set the project name.
+      #
+      # @param project_name [String]
+      #   Project name.
       def project_name(project_name)
         @script.project_name = project_name
       end
 
-      # Whether to automatically configure (default true).
+      # Set whether to automatically configure (default true).
+      #
+      # @param autoconf [Boolean]
+      #   Whether to automatically configure.
       def autoconf(autoconf)
         @script.autoconf = autoconf
       end

lib/rscons/util.rb

@@ -16,6 +16,42 @@ module Rscons
         end
       end
 
+      # Get the absolute path for a given path.
+      #
+      # If the path is a phony target, leave it as is.
+      #
+      # @param path [String, Symbol]
+      #   Input path.
+      #
+      # @return [String, Symbol]
+      #   Output path.
+      def absolute_path(path)
+        if Rscons.phony_target?(path)
+          path
+        else
+          File.expand_path(path)
+        end
+      end
+
+      # Remove any stale .di files from the precompile path.
+      #
+      # @param pc_path [String]
+      #   Path to precompile build directory containing .di generated
+      #   interface files.
+      # @param import_path [String]
+      #   D import path containing .d source files.
+      #
+      # @return [void]
+      def clean_d_precompile_path(pc_path, import_path)
+        glob("#{pc_path}/**/*.di").each do |di_path|
+          end_path = di_path[(pc_path.size+1)..]
+          path = "#{import_path}/#{end_path}".sub(/\.di$/, ".d")
+          unless File.exist?(path)
+            FileUtils.rm_f(path)
+          end
+        end
+      end
+
       # Colorize a builder run message.
       #
       # @param message [String]
@@ -120,6 +156,29 @@ module Rscons
         end
       end
 
+      # Find the D import path that will be used to import the given module.
+      #
+      # @param import_paths [Array<String>]
+      #   Import paths.
+      # @param source [String]
+      #   Source file name.
+      # @param module_name [String]
+      #   Module name.
+      #
+      # @return [String, nil]
+      #   Import path used to import the given module.
+      def find_import_path_for_d_source(import_paths, source, module_name)
+        source = source.gsub("\\", "/")
+        module_path = module_name.gsub(".", "/") + ".d"
+        import_paths.each do |import_path|
+          path = "#{import_path}/#{module_path}".gsub("\\", "/")
+          if path == source
+            return import_path
+          end
+        end
+        nil
+      end
+
       # Format an elapsed time in human-readable format.
       #
       # @return [String]
@@ -141,6 +200,52 @@ module Rscons
         result
       end
 
+      # Get the module name for a D source file.
+      #
+      # @param source_path [String]
+      #   D source file.
+      #
+      # @return [String, nil]
+      #   Module name.
+      def get_module_name(source_path)
+        if File.exist?(source_path)
+          if File.binread(source_path) =~ /^\s*module\s(\S*);/
+            return $1
+          end
+          name = File.basename(source_path).sub(/\.d$/, "")
+          if name =~ /^\w+$/
+            return name
+          end
+        end
+      end
+
+      # Return a list of paths matching the specified pattern(s).
+      #
+      # A pattern can contain a "/**" component to recurse through directories.
+      # If the pattern ends with "/**" then only the recursive list of
+      # directories will be returned.
+      #
+      # Examples:
+      # - "src/**": return all directories under "src", recursively (including
+      #   "src" itself).
+      # - "src/**/*": return all files and directories recursively under the src
+      #   directory.
+      # - "src/**/*.c": return all .c files recursively under the src directory.
+      # - "dir/*/": return all directories in dir, but no files.
+      #
+      # @return [Array<String>] Paths matching the specified pattern(s).
+      def glob(*patterns)
+        require "pathname"
+        patterns.reduce([]) do |result, pattern|
+          if pattern.end_with?("/**")
+            pattern += "/"
+          end
+          result += Dir.glob(pattern).map do |path|
+            Pathname.new(path.gsub("\\", "/")).cleanpath.to_s
+          end
+        end.sort
+      end
+
       # Make a relative path corresponding to a possibly absolute one.
       #
       # @param path [String]

lib/rscons/version.rb

@@ -1,4 +1,4 @@
 module Rscons
   # Project version.
-  VERSION = "2.3.0"
+  VERSION = "3.3.0"
 end

rb/build_dist.rb

@@ -1,7 +1,10 @@
 #!/usr/bin/env ruby
 
-require "fileutils"
+require "base64"
 require "digest/md5"
+require "fileutils"
+require "stringio"
+require "zlib"
 
 if File.read("lib/rscons/version.rb") =~ /VERSION = "(.+)"/
   VERSION = $1
@@ -22,7 +25,7 @@ combine_files = lambda do |file|
       require_name = $1
       if require_name =~ %r{^#{PROG_NAME}(?:/.*)?$}
         path = "#{LIB_DIR}/#{require_name}.rb"
-        if File.exists?(path)
+        if File.exist?(path)
           unless files_processed[path]
             files_processed[path] = true
             combine_files[path]
@@ -60,13 +63,23 @@ combined_file.each do |line|
   end
 end
 
-license = File.read("LICENSE.txt").gsub(/^/, "# ")
+license = File.read("LICENSE.txt").gsub(/^(.*?)$/) do |line|
+  if line.size > 0
+    "# #{line}"
+  else
+    "#"
+  end
+end
 
-require "zlib"
-require "base64"
 compressed_script = Zlib::Deflate.deflate(stripped.join)
+hash = Digest::MD5.hexdigest(compressed_script)
 encoded_compressed_script = Base64.encode64(compressed_script).gsub("\n", "")
-hash = Digest::MD5.hexdigest(encoded_compressed_script)
+encoded_compressed_script_io = StringIO.new(encoded_compressed_script)
+commented_encoded_compressed_script = ""
+until encoded_compressed_script_io.eof?
+  line = encoded_compressed_script_io.read(64)
+  commented_encoded_compressed_script += "##{line}\n"
+end
 
 FileUtils.rm_rf(DIST)
 FileUtils.mkdir_p(DIST)
@@ -76,25 +89,53 @@ File.open("#{DIST}/#{PROG_NAME}", "wb", 0755) do |fh|
 
 #{license}
 
+BASE64CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+
+def base64_decode(s)
+  out = ""
+  v = 0
+  bits = 0
+  s.each_char do |c|
+    if cv = BASE64CHARS.index(c)
+      v = (v << 6) | cv
+      bits += 6
+    elsif c == "="
+      break
+    end
+    if bits >= 8
+      out += (v >> (bits - 8)).chr
+      v &= 0xFFFFFFFF >> (32 - (bits - 8))
+      bits -= 8
+    end
+  end
+  out
+end
+
 script = File.join(File.dirname(__FILE__), ".rscons-#{VERSION}-#{hash}.rb")
-unless File.exists?(script)
-  if File.read(__FILE__, mode: "rb") =~ /^#==>(.*)/
+unless File.exist?(script)
+  if File.read(__FILE__, mode: "rb") =~ /^#==>(.*)/m
     require "zlib"
-    require "base64"
     encoded_compressed = $1
-    unescaped_compressed = Base64.decode64(encoded_compressed)
-    inflated = Zlib::Inflate.inflate(unescaped_compressed)
+    compressed = base64_decode(encoded_compressed)
+    if ENV["rscons_dist_specs"]
+      require "digest/md5"
+      if Digest::MD5.hexdigest(compressed) != "#{hash}"
+        raise "Hash mismatch when decompressing rscons executable"
+      end
+    end
+    inflated = Zlib::Inflate.inflate(compressed)
     File.open(script, "wb") do |fh|
       fh.write(inflated)
     end
   else
-    raise "Could not decompress."
+    raise "Error expanding rscons executable"
   end
 end
 load script
 if __FILE__ == $0
   Rscons::Cli.new.run(ARGV)
 end
-#==>#{encoded_compressed_script}
+#==>
+#{commented_encoded_compressed_script}
 EOF
 end

rb/gen_user_guide.rb

@@ -99,7 +99,7 @@ class Generator
     end
 
     template = File.read("rb/assets/user_guide.html.erb")
-    erb = ERB.new(template, nil, "<>")
+    erb = ERB.new(template, trim_mode: "<>")
 
     if multi_page
       @pages.each_with_index do |page, page_index|

spec/rscons/cache_spec.rb

@@ -17,14 +17,14 @@ module Rscons
       it "makes directories and records any created in the cache" do
         _cache = {}
         cache = build_from(_cache)
-        expect(File).to receive(:exists?).with("one").and_return(true)
-        expect(File).to receive(:exists?).with("one/two").and_return(false)
+        expect(File).to receive(:exist?).with("one").and_return(true)
+        expect(File).to receive(:exist?).with("one/two").and_return(false)
         expect(FileUtils).to receive(:mkdir_p).with("one/two")
-        expect(File).to receive(:exists?).with("one/two/three").and_return(false)
+        expect(File).to receive(:exist?).with("one/two/three").and_return(false)
         expect(FileUtils).to receive(:mkdir_p).with("one/two/three")
-        expect(File).to receive(:exists?).with("one").and_return(true)
-        expect(File).to receive(:exists?).with("one/two").and_return(true)
-        expect(File).to receive(:exists?).with("one/two/four").and_return(false)
+        expect(File).to receive(:exist?).with("one").and_return(true)
+        expect(File).to receive(:exist?).with("one/two").and_return(true)
+        expect(File).to receive(:exist?).with("one/two/four").and_return(false)
         expect(FileUtils).to receive(:mkdir_p).with("one/two/four")
         cache.mkdir_p("one/two/three")
         cache.mkdir_p("one\\two\\four")
@@ -34,8 +34,8 @@ module Rscons
       it "handles absolute paths" do
         _cache = {}
         cache = build_from(_cache)
-        expect(File).to receive(:exists?).with("/one").and_return(true)
-        expect(File).to receive(:exists?).with("/one/two").and_return(false)
+        expect(File).to receive(:exist?).with("/one").and_return(true)
+        expect(File).to receive(:exist?).with("/one/two").and_return(false)
         expect(FileUtils).to receive(:mkdir_p).with("/one/two")
         cache.mkdir_p("/one/two")
         expect(cache.directories(false)).to eq ["/one/two"]

spec/spec_helper.rb

@@ -1,4 +1,4 @@
-if ENV["dist_specs"]
+if ENV["rscons_dist_specs"]
   require_relative "../test/rscons"
 else
   require "simplecov"
@@ -11,12 +11,7 @@ else
     else
       command_name "RSpec"
     end
-    if ENV["dist_specs"]
-      add_filter "/bin/"
-      add_filter "/lib/"
-    else
-      add_filter "test/rscons.rb"
-    end
+    add_filter "test/rscons.rb"
     project_name "Rscons"
     merge_timeout 3600
   end