diff --git a/lib/rubygems/commands/install_command.rb b/lib/rubygems/commands/install_command.rb
index 6d3beec0b432..5e7a5a410670 100644
--- a/lib/rubygems/commands/install_command.rb
+++ b/lib/rubygems/commands/install_command.rb
@@ -93,7 +93,7 @@ def description # :nodoc:
   [build fails]
   Gem files will remain installed in \\
   /path/to/gems/some_extension_gem-1.0 for inspection.
-  Results logged to /path/to/gems/some_extension_gem-1.0/gem_make.out
+  Results logged to /path/to/build_info/some_extension_gem-1.0.gem_make.out
   $ gem install some_extension_gem -- --with-extension-lib=/path/to/lib
   [build succeeds]
   $ gem list some_extension_gem
@@ -110,7 +110,7 @@ def description # :nodoc:
   [build fails]
   Gem files will remain installed in \\
   /path/to/gems/some_extension_gem-1.0 for inspection.
-  Results logged to /path/to/gems/some_extension_gem-1.0/gem_make.out
+  Results logged to /path/to/build_info/some_extension_gem-1.0.gem_make.out
   $ [cd /path/to/gems/some_extension_gem-1.0]
   $ [edit files or what-have-you and run make]
   $ gem spec ../../cache/some_extension_gem-1.0.gem --ruby > \\
diff --git a/lib/rubygems/ext/builder.rb b/lib/rubygems/ext/builder.rb
index 53a02f61f31b..ca1b4c2db615 100644
--- a/lib/rubygems/ext/builder.rb
+++ b/lib/rubygems/ext/builder.rb
@@ -222,9 +222,25 @@ def build_extension(extension, dest_path) # :nodoc:
 
       verbose { results.join("\n") }
 
-      write_gem_make_out results.join "\n"
+      # mkmf.log is a noisy, non-reproducible build artifact that is not meant
+      # to be installed. Drop the one left behind by a successful build instead
+      # of leaving it in the installation tree.
+      FileUtils.rm_f File.join(extension_dir, "mkmf.log")
     rescue StandardError => e
       results << e.message
+
+      # On failure keep the mkmf.log for inspection, but move it out of the
+      # installation tree into the build_info directory.
+      mkmf_log = File.join extension_dir, "mkmf.log"
+      if File.exist?(mkmf_log)
+        mkmf_log_dest = File.join @spec.build_info_dir, "#{@spec.full_name}.mkmf.log"
+        FileUtils.mkdir_p @spec.build_info_dir
+        FileUtils.mv mkmf_log, mkmf_log_dest
+
+        results << "To see why this extension failed to compile, please check the mkmf.log which can be found here:"
+        results << "  #{mkmf_log_dest}"
+      end
+
       build_error(results.join("\n"), $@)
     end
   end
@@ -256,12 +272,14 @@ def build_extensions
   end
 
   ##
-  # Writes +output+ to gem_make.out in the extension install directory.
+  # Writes +output+ to gem_make.out in the build_info directory. Only called
+  # on failure (via #build_error), to keep build logs out of the installation
+  # tree.
 
   def write_gem_make_out(output) # :nodoc:
-    destination = File.join @spec.extension_dir, "gem_make.out"
+    destination = File.join @spec.build_info_dir, "#{@spec.full_name}.gem_make.out"
 
-    FileUtils.mkdir_p @spec.extension_dir
+    FileUtils.mkdir_p @spec.build_info_dir
 
     File.open destination, "wb" do |io|
       io.puts output
diff --git a/lib/rubygems/ext/ext_conf_builder.rb b/lib/rubygems/ext/ext_conf_builder.rb
index 822454355d10..a658e0b0eb59 100644
--- a/lib/rubygems/ext/ext_conf_builder.rb
+++ b/lib/rubygems/ext/ext_conf_builder.rb
@@ -27,17 +27,10 @@ def self.build(extension, dest_path, results, args = [], lib_dir = nil, extensio
       cmd << "--target-rbconfig=#{target_rbconfig.path}" if target_rbconfig.path
       cmd.push(*args)
 
-      run(cmd, results, class_name, extension_dir) do |s, r|
-        mkmf_log = File.join(extension_dir, "mkmf.log")
-        if File.exist? mkmf_log
-          unless s.success?
-            r << "To see why this extension failed to compile, please check" \
-              " the mkmf.log which can be found here:\n"
-            r << "  " + File.join(dest_path, "mkmf.log") + "\n"
-          end
-          FileUtils.mv mkmf_log, dest_path
-        end
-      end
+      # Leave mkmf.log in the extension directory. The final placement (dropped
+      # on success, moved to build_info on failure) is decided by
+      # Gem::Ext::Builder#build_extension.
+      run(cmd, results, class_name, extension_dir)
 
       ENV["DESTDIR"] = nil
 
diff --git a/lib/rubygems/uninstaller.rb b/lib/rubygems/uninstaller.rb
index fe4c3a80cf92..ff4982d9945f 100644
--- a/lib/rubygems/uninstaller.rb
+++ b/lib/rubygems/uninstaller.rb
@@ -271,6 +271,8 @@ def remove(spec)
 
     safe_delete { rm_r full_gem_path, exclusions: exclusions }
     safe_delete { FileUtils.rm_r spec.extension_dir }
+    safe_delete { FileUtils.rm_f File.join(spec.build_info_dir, "#{spec.full_name}.mkmf.log") }
+    safe_delete { FileUtils.rm_f File.join(spec.build_info_dir, "#{spec.full_name}.gem_make.out") }
 
     old_platform_name = spec.original_name
 
diff --git a/spec/bundler/installer/parallel_installer_spec.rb b/spec/bundler/installer/parallel_installer_spec.rb
index 528dc1ae93e5..be62ae59d0a6 100644
--- a/spec/bundler/installer/parallel_installer_spec.rb
+++ b/spec/bundler/installer/parallel_installer_spec.rb
@@ -147,34 +147,37 @@
     let(:gem_two) { definition.specs.find {|spec| spec.name == "two" } }
 
     it "takes all available slots" do
-      redefine_build_jobs do
+      acquired = track_build_jobs(rendezvous: true) do
         Bundler::ParallelInstaller.call(installer, definition.specs, 5, false, true)
       end
 
-      # Take 3 slots out of the 5 available.
-      expect(File.read(File.join(gem_one.extension_dir, "gem_make.out"))).to include("make -j3")
+      # Take 3 slots (capped per gem) out of the 5 available.
+      expect(acquired["one"]).to eq(3)
       # Take the remaining 2 slots.
-      expect(File.read(File.join(gem_two.extension_dir, "gem_make.out"))).to include("make -j2")
+      expect(acquired["two"]).to eq(2)
     end
 
     it "fallback to non parallel when no slots are available" do
-      redefine_build_jobs do
+      acquired = track_build_jobs(rendezvous: true) do
         Bundler::ParallelInstaller.call(installer, definition.specs, 3, false, true)
       end
 
       # Take 3 slots out of the 3 available.
-      expect(File.read(File.join(gem_one.extension_dir, "gem_make.out"))).to include("make -j3")
+      expect(acquired["one"]).to eq(3)
       # Fallback to one slot (non parallel).
-      expect(File.read(File.join(gem_two.extension_dir, "gem_make.out"))).to_not include("make -j")
+      expect(acquired["two"]).to eq(1)
     end
 
     it "uses one jobs when installing serially" do
+      acquired = nil
       Bundler.settings.temporary(jobs: 1) do
-        Bundler::ParallelInstaller.call(installer, definition.specs, 1, false, true)
+        acquired = track_build_jobs do
+          Bundler::ParallelInstaller.call(installer, definition.specs, 1, false, true)
+        end
       end
 
-      expect(File.read(File.join(gem_one.extension_dir, "gem_make.out"))).to_not include("make -j")
-      expect(File.read(File.join(gem_two.extension_dir, "gem_make.out"))).to_not include("make -j")
+      expect(acquired["one"]).to eq(1)
+      expect(acquired["two"]).to eq(1)
     end
 
     it "release the job slots" do
@@ -186,39 +189,52 @@
         end
       end
 
-      Bundler::ParallelInstaller.call(installer, definition.specs, 3, false, true)
+      acquired = track_build_jobs do
+        Bundler::ParallelInstaller.call(installer, definition.specs, 3, false, true)
+      end
 
       # Take 3 slots out of the 3 available.
-      expect(File.read(File.join(gem_one.extension_dir, "gem_make.out"))).to include("make -j3")
-      # Take 3 slots that were released.
-      expect(File.read(File.join(gem_two.extension_dir, "gem_make.out"))).to include("make -j3")
+      expect(acquired["one"]).to eq(3)
+      # Take 3 slots that were released by `one`.
+      expect(acquired["two"]).to eq(3)
     end
 
-    def redefine_build_jobs
+    # Records how many jobserver slots each gem's build acquired. RubyGems turns
+    # that count directly into `make -jN`, so asserting on it verifies slot
+    # allocation and release without reading a build log, which a successful
+    # build no longer writes. With +rendezvous+, "one" grabs its slots first and
+    # holds them until "two" has grabbed the rest, making the split deterministic.
+    def track_build_jobs(rendezvous: false)
+      acquired = {}
       old_method = Bundler::RubyGemsGemInstaller.instance_method(:build_jobs)
       Bundler::RubyGemsGemInstaller.remove_method(:build_jobs)
 
-      # Rendezvous so that "one" grabs its slots first and keeps holding them
-      # until "two" has grabbed the rest. Blocking on a queue avoids the
-      # busy-wait and makes the ordering deterministic.
       one_acquired = Thread::Queue.new
       two_acquired = Thread::Queue.new
 
       Bundler::RubyGemsGemInstaller.define_method(:build_jobs) do
-        if spec.name == "one"
-          value = old_method.bind(self).call
-          one_acquired << true
-          two_acquired.pop
-        elsif spec.name == "two"
-          one_acquired.pop
-          value = old_method.bind(self).call
-          two_acquired << true
-        end
+        value =
+          if rendezvous && spec.name == "one"
+            v = old_method.bind(self).call
+            one_acquired << true
+            two_acquired.pop
+            v
+          elsif rendezvous && spec.name == "two"
+            one_acquired.pop
+            v = old_method.bind(self).call
+            two_acquired << true
+            v
+          else
+            old_method.bind(self).call
+          end
 
+        acquired[spec.name] = value
         value
       end
 
       yield
+
+      acquired
     ensure
       Bundler::RubyGemsGemInstaller.remove_method(:build_jobs)
       Bundler::RubyGemsGemInstaller.define_method(:build_jobs, old_method)
diff --git a/spec/commands/install_spec.rb b/spec/commands/install_spec.rb
index f8a134f23108..7048c0f4d253 100644
--- a/spec/commands/install_spec.rb
+++ b/spec/commands/install_spec.rb
@@ -1369,10 +1369,18 @@ def run
           s.extensions = extension
 
           s.write(extension, extconf_code)
+          # A successful build no longer leaves gem_make.out behind. Force the
+          # build to fail at the make stage so the make command line, including
+          # the jobserver `-j`, is recorded in build_info for these assertions.
+          s.write("ext/mypsych/mypsych.c", "#error forced build failure for test")
         end
       end
     end
 
+    def gem_make_out
+      File.read(File.join(@gemspec.build_info_dir, "#{@gemspec.full_name}.gem_make.out"))
+    end
+
     after do
       if @old_makeflags
         ENV["MAKEFLAGS"] = @old_makeflags
@@ -1384,39 +1392,33 @@ def run
     it "doesn't pass down -j to make when MAKEFLAGS is set" do
       ENV["MAKEFLAGS"] = "-j1"
 
-      install_gemfile(<<~G, env: { "BUNDLE_JOBS" => "8" })
+      install_gemfile(<<~G, env: { "BUNDLE_JOBS" => "8" }, raise_on_error: false)
         source "https://gem.repo4"
         gem "mypsych"
       G
 
-      gem_make_out = File.read(File.join(@gemspec.extension_dir, "gem_make.out"))
-
       expect(gem_make_out).not_to include("make -j8")
     end
 
     it "uses 3 slots from the available pool when running the compilation of an extension" do
       ENV.delete("MAKEFLAGS")
 
-      install_gemfile(<<~G, env: { "BUNDLE_JOBS" => "8" })
+      install_gemfile(<<~G, env: { "BUNDLE_JOBS" => "8" }, raise_on_error: false)
         source "https://gem.repo4"
         gem "mypsych"
       G
 
-      gem_make_out = File.read(File.join(@gemspec.extension_dir, "gem_make.out"))
-
       expect(gem_make_out).to include("make -j3")
     end
 
     it "consumes 3 slots from the pool when BUNDLE_JOBS isn't set" do
       ENV.delete("MAKEFLAGS")
 
-      install_gemfile(<<~G)
+      install_gemfile(<<~G, raise_on_error: false)
         source "https://gem.repo4"
         gem "mypsych"
       G
 
-      gem_make_out = File.read(File.join(@gemspec.extension_dir, "gem_make.out"))
-
       expect(gem_make_out).to include("make -j3")
     end
   end
diff --git a/test/rubygems/test_gem_commands_install_command.rb b/test/rubygems/test_gem_commands_install_command.rb
index d75ba349f96a..39b6e5951df7 100644
--- a/test/rubygems/test_gem_commands_install_command.rb
+++ b/test/rubygems/test_gem_commands_install_command.rb
@@ -1587,6 +1587,9 @@ def test_pass_down_the_job_option_to_make
 
         write_file(extconf_path) do |io|
           io.puts "require 'mkmf'"
+          # Force the build to fail at the make stage so the build log is
+          # written. The make command line (including -j) is recorded there.
+          io.puts "File.write('a.c', '#error forced build failure for test')"
           io.puts "create_makefile '#{spec.name}'"
         end
 
@@ -1595,12 +1598,12 @@ def test_pass_down_the_job_option_to_make
     end
 
     use_ui @ui do
-      assert_raise Gem::MockGemUi::SystemExitException, @ui.error do
+      assert_raise Gem::MockGemUi::TermError, @ui.error do
         @cmd.invoke "a", "-j4"
       end
     end
 
-    gem_make_out = File.read(File.join(gemspec.extension_dir, "gem_make.out"))
+    gem_make_out = File.read(File.join(gemspec.build_info_dir, "#{gemspec.full_name}.gem_make.out"))
     if vc_windows? && nmake_found?
       refute_includes(gem_make_out, " -j4")
     else
diff --git a/test/rubygems/test_gem_commands_update_command.rb b/test/rubygems/test_gem_commands_update_command.rb
index 5bc36d61035e..ec5c762b89dd 100644
--- a/test/rubygems/test_gem_commands_update_command.rb
+++ b/test/rubygems/test_gem_commands_update_command.rb
@@ -735,6 +735,9 @@ def test_pass_down_the_job_option_to_make
 
         write_file(extconf_path) do |io|
           io.puts "require 'mkmf'"
+          # Force the build to fail at the make stage so the build log is
+          # written. The make command line (including -j) is recorded there.
+          io.puts "File.write('a.c', '#error forced build failure for test')"
           io.puts "create_makefile '#{spec.name}'"
         end
 
@@ -748,7 +751,7 @@ def test_pass_down_the_job_option_to_make
       @cmd.invoke("a", "-j2")
     end
 
-    gem_make_out = File.read(File.join(gemspec.extension_dir, "gem_make.out"))
+    gem_make_out = File.read(File.join(gemspec.build_info_dir, "#{gemspec.full_name}.gem_make.out"))
     if vc_windows? && nmake_found?
       refute_includes(gem_make_out, " -j2")
     else
diff --git a/test/rubygems/test_gem_ext_builder.rb b/test/rubygems/test_gem_ext_builder.rb
index 37204f3c472a..5285d7af1308 100644
--- a/test/rubygems/test_gem_ext_builder.rb
+++ b/test/rubygems/test_gem_ext_builder.rb
@@ -154,7 +154,9 @@ def test_build_extensions
 
       assert_path_exist @spec.extension_dir
       assert_path_exist @spec.gem_build_complete_path
-      assert_path_exist File.join @spec.extension_dir, "gem_make.out"
+      assert_path_not_exist File.join @spec.extension_dir, "gem_make.out"
+      assert_path_not_exist File.join @spec.extension_dir, "mkmf.log"
+      assert_path_not_exist File.join @spec.gem_dir, "ext", "mkmf.log"
       assert_path_exist File.join @spec.extension_dir, "a.rb"
       assert_path_exist File.join @spec.gem_dir, "lib", "a.rb"
       assert_path_exist File.join @spec.gem_dir, "lib", "a", "b.rb"
@@ -208,7 +210,9 @@ def test_build_extensions_install_ext_only
 
       assert_path_exist @spec.extension_dir
       assert_path_exist @spec.gem_build_complete_path
-      assert_path_exist File.join @spec.extension_dir, "gem_make.out"
+      assert_path_not_exist File.join @spec.extension_dir, "gem_make.out"
+      assert_path_not_exist File.join @spec.extension_dir, "mkmf.log"
+      assert_path_not_exist File.join @spec.gem_dir, "ext", "mkmf.log"
       assert_path_exist File.join @spec.extension_dir, "a.rb"
       assert_path_not_exist File.join @spec.gem_dir, "lib", "a.rb"
       assert_path_not_exist File.join @spec.gem_dir, "lib", "a", "b.rb"
@@ -261,13 +265,88 @@ def test_build_multiple_extensions
       assert_path_exist @spec.extension_dir
       assert_path_exist @spec.gem_build_complete_path
       assert_path_exist File.join @spec.gem_dir, "ext", "foo"
-      assert_path_exist File.join @spec.extension_dir, "gem_make.out"
+      assert_path_not_exist File.join @spec.extension_dir, "gem_make.out"
+      assert_path_not_exist File.join @spec.extension_dir, "mkmf.log"
+      assert_path_not_exist File.join @spec.gem_dir, "ext", "mkmf.log"
       assert_path_exist File.join @spec.extension_dir, "a.rb"
       assert_path_exist File.join @spec.gem_dir, "lib", "a.rb"
       assert_path_exist File.join @spec.gem_dir, "lib", "a", "b.rb"
     end
   end
 
+  def test_build_extensions_does_not_install_logs_on_success
+    pend "terminates on mswin" if vc_windows? && ruby_repo?
+
+    @spec.extensions << "ext/extconf.rb"
+
+    ext_dir = File.join @spec.gem_dir, "ext"
+    FileUtils.mkdir_p ext_dir
+
+    File.open File.join(ext_dir, "extconf.rb"), "w" do |f|
+      f.write <<-'RUBY'
+        require 'mkmf'
+
+        create_makefile 'a'
+      RUBY
+    end
+
+    use_ui @ui do
+      @builder.build_extensions
+    end
+
+    assert_path_exist @spec.gem_build_complete_path
+
+    # No build logs are left anywhere in the installation tree.
+    assert_path_not_exist File.join @spec.extension_dir, "gem_make.out"
+    assert_path_not_exist File.join @spec.extension_dir, "mkmf.log"
+    assert_path_not_exist File.join ext_dir, "mkmf.log"
+    assert_path_not_exist File.join ext_dir, "gem_make.out"
+    assert_path_not_exist File.join @spec.build_info_dir, "#{@spec.full_name}.mkmf.log"
+    assert_path_not_exist File.join @spec.build_info_dir, "#{@spec.full_name}.gem_make.out"
+  end
+
+  def test_build_extensions_logs_to_build_info_on_failure
+    pend "terminates on mswin" if vc_windows? && ruby_repo?
+
+    @spec.extensions << "ext/extconf.rb"
+
+    ext_dir = File.join @spec.gem_dir, "ext"
+    FileUtils.mkdir_p ext_dir
+
+    File.open File.join(ext_dir, "extconf.rb"), "w" do |f|
+      f.write <<-'RUBY'
+        require 'mkmf'
+
+        have_library 'nonexistent' or abort 'need libnonexistent'
+
+        create_makefile 'a'
+      RUBY
+    end
+
+    e = assert_raise Gem::Ext::BuildError do
+      use_ui @ui do
+        @builder.build_extensions
+      end
+    end
+
+    mkmf_log = File.join @spec.build_info_dir, "#{@spec.full_name}.mkmf.log"
+    gem_make_out = File.join @spec.build_info_dir, "#{@spec.full_name}.gem_make.out"
+
+    assert_path_exist mkmf_log
+    assert_path_exist gem_make_out
+
+    # Logs are not left in the installation tree.
+    assert_path_not_exist File.join @spec.extension_dir, "mkmf.log"
+    assert_path_not_exist File.join @spec.extension_dir, "gem_make.out"
+    assert_path_not_exist File.join ext_dir, "mkmf.log"
+
+    # The error message points at the new build_info paths.
+    assert_includes e.message, gem_make_out
+    assert_includes e.message, mkmf_log
+
+    assert_path_not_exist @spec.gem_build_complete_path
+  end
+
   def test_build_extensions_none
     use_ui @ui do
       @builder.build_extensions
@@ -311,12 +390,14 @@ def test_build_extensions_extconf_bad
     assert_equal "Building native extensions. This could take a while...\n", @ui.output
     assert_equal "", @ui.error
 
-    gem_make_out = File.join @spec.extension_dir, "gem_make.out"
+    gem_make_out = File.join @spec.build_info_dir, "#{@spec.full_name}.gem_make.out"
     cmd_make_out = File.read(gem_make_out)
 
     assert_match %r{#{Regexp.escape Gem.ruby} .* extconf\.rb}, cmd_make_out
     assert_match(/: No such file/, cmd_make_out)
 
+    assert_path_not_exist File.join @spec.extension_dir, "gem_make.out"
+
     assert_path_not_exist @spec.gem_build_complete_path
 
     assert_equal cwd, Dir.pwd
@@ -324,7 +405,7 @@ def test_build_extensions_extconf_bad
 
   def test_build_extensions_unsupported
     FileUtils.mkdir_p @spec.gem_dir
-    gem_make_out = File.join @spec.extension_dir, "gem_make.out"
+    gem_make_out = File.join @spec.build_info_dir, "#{@spec.full_name}.gem_make.out"
     @spec.extensions << nil
 
     e = assert_raise Gem::Ext::BuildError do
diff --git a/test/rubygems/test_gem_ext_ext_conf_builder.rb b/test/rubygems/test_gem_ext_ext_conf_builder.rb
index bc383e5540a9..e14013899559 100644
--- a/test/rubygems/test_gem_ext_ext_conf_builder.rb
+++ b/test/rubygems/test_gem_ext_ext_conf_builder.rb
@@ -110,10 +110,12 @@ def test_class_build_extconf_fail
     assert_equal "extconf failed, exit code 1", error.message
 
     assert_match(/^#{Regexp.quote(Gem.ruby)}.* extconf.rb/, output[1])
-    assert_match(File.join(@dest_path, "mkmf.log"), output[4])
-    assert_includes(output, "To see why this extension failed to compile, please check the mkmf.log which can be found here:\n")
+    refute_includes(output, "To see why this extension failed to compile, please check the mkmf.log which can be found here:\n")
 
-    assert_path_exist File.join @dest_path, "mkmf.log"
+    # mkmf.log is left in the extension directory; deciding where it ends up is
+    # left to Gem::Ext::Builder#build_extension.
+    assert_path_exist File.join @ext, "mkmf.log"
+    assert_path_not_exist File.join @dest_path, "mkmf.log"
   end
 
   def test_class_build_extconf_success_without_warning
@@ -133,7 +135,10 @@ def test_class_build_extconf_success_without_warning
 
     refute_includes(output, "To see why this extension failed to compile, please check the mkmf.log which can be found here:\n")
 
-    assert_path_exist File.join @dest_path, "mkmf.log"
+    # On a successful build, mkmf.log is cleaned up by "make clean" and is never
+    # copied into the install destination.
+    assert_path_not_exist File.join @ext, "mkmf.log"
+    assert_path_not_exist File.join @dest_path, "mkmf.log"
   end
 
   def test_class_build_unconventional
diff --git a/test/rubygems/test_gem_specification.rb b/test/rubygems/test_gem_specification.rb
index 79be0c996d23..a82abe5cb30f 100644
--- a/test/rubygems/test_gem_specification.rb
+++ b/test/rubygems/test_gem_specification.rb
@@ -1562,8 +1562,9 @@ def test_build_extensions_preview
 
     @ext.build_extensions
 
+    # A successful build no longer leaves gem_make.out in the install tree.
     gem_make_out = File.join @ext.extension_dir, "gem_make.out"
-    assert_path_exist gem_make_out
+    assert_path_not_exist gem_make_out
   end
 
   def test_contains_requirable_file_eh
diff --git a/test/rubygems/test_gem_uninstaller.rb b/test/rubygems/test_gem_uninstaller.rb
index 92ea01a3bca2..f4ce4e0e04e3 100644
--- a/test/rubygems/test_gem_uninstaller.rb
+++ b/test/rubygems/test_gem_uninstaller.rb
@@ -391,6 +391,39 @@ def test_uninstall_extension
     assert_path_not_exist @spec.extension_dir
   end
 
+  def test_uninstall_removes_build_info_logs
+    @spec.extensions << "extconf.rb"
+    write_file File.join(@tempdir, "extconf.rb") do |io|
+      io.write <<-RUBY
+require 'mkmf'
+create_makefile '#{@spec.name}'
+      RUBY
+    end
+
+    @spec.files += %w[extconf.rb]
+
+    use_ui @ui do
+      path = Gem::Package.build @spec
+
+      installer = Gem::Installer.at path, force: true
+      installer.install
+    end
+
+    # Build logs left behind in build_info by a previous failed build.
+    FileUtils.mkdir_p @spec.build_info_dir
+    mkmf_log = File.join @spec.build_info_dir, "#{@spec.full_name}.mkmf.log"
+    gem_make_out = File.join @spec.build_info_dir, "#{@spec.full_name}.gem_make.out"
+    FileUtils.touch mkmf_log
+    FileUtils.touch gem_make_out
+
+    uninstaller = Gem::Uninstaller.new @spec.name, executables: true
+    uninstaller.uninstall
+
+    assert_path_not_exist @spec.extension_dir
+    assert_path_not_exist mkmf_log
+    assert_path_not_exist gem_make_out
+  end
+
   def test_uninstall_nonexistent
     uninstaller = Gem::Uninstaller.new "bogus", executables: true