Place object files next to source files for source files in build directory - close #171

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

lib/rscons/environment.rb

@@ -277,7 +277,15 @@ module Rscons
       if extra_path = builder_class.extra_path
         extra_path = "/#{extra_path}"
       end
-      "#{@build_root}/o#{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
 
     # Build all build targets specified in the Environment.

spec/build_tests_spec.rb

@@ -990,6 +990,14 @@ EOF
     verify_lines(slines, [%r{\babs.exe\b}])
   end
 
+  it "creates object files next to the source file for source files in the build root" do
+    test_dir "simple"
+    result = run_rscons(args: %w[-f build_root_source_path.rb])
+    expect(result.stderr).to eq ""
+    expect(File.exist?("build/e/o/build/e/src/foo.c.o")).to be_falsey
+    expect(File.exist?("build/e/src/foo.c.o")).to be_truthy
+  end
+
   it "creates shared libraries" do
     test_dir("shared_library")