Index: libcxx/trunk/test/lit.cfg
===================================================================
--- libcxx/trunk/test/lit.cfg
+++ libcxx/trunk/test/lit.cfg
@@ -45,7 +45,7 @@
         if in_dir:
             kwargs['cwd'] = in_dir
         p = subprocess.Popen(command, **kwargs)
-        out,err = p.communicate()
+        out, err = p.communicate()
         exitCode = p.wait()
 
         # Detect Ctrl-C in subprocess.
@@ -108,6 +108,37 @@
         # Evaluate the test.
         return self._evaluate_test(test, use_verify, lit_config)
 
+    def _build(self, exec_path, source_path, compile_only=False,
+               use_verify=False):
+        cmd = [self.cxx_under_test, '-o', exec_path,
+               source_path] + self.cpp_flags
+
+        if compile_only:
+            cmd += ['-c']
+        else:
+            cmd += self.ld_flags
+
+        if use_verify:
+            cmd += ['-Xclang', '-verify']
+
+        out, err, rc = self.execute_command(cmd)
+        return cmd, out, err, rc
+
+    def _clean(self, exec_path):
+        os.remove(exec_path)
+
+    def _run(self, exec_path, lit_config, in_dir=None):
+        cmd = []
+        if self.exec_env:
+            cmd.append('env')
+            cmd.extend('%s=%s' % (name, value)
+                       for name,value in self.exec_env.items())
+        cmd.append(exec_path)
+        if lit_config.useValgrind:
+            cmd = lit_config.valgrindArgs + cmd
+        out, err, exitCode = self.execute_command(cmd, in_dir)
+        return cmd, out, err, exitCode
+
     def _evaluate_test(self, test, use_verify, lit_config):
         name = test.path_in_suite[-1]
         source_path = test.getSourcePath()
@@ -119,13 +150,10 @@
 
         # If this is a compile (failure) test, build it and check for failure.
         if expected_compile_fail:
-            cmd = [self.cxx_under_test, '-c',
-                   '-o', '/dev/null', source_path] + self.cpp_flags
-            expected_rc = 1
-            if use_verify:
-                cmd += ['-Xclang', '-verify']
-                expected_rc = 0
-            out, err, rc = self.execute_command(cmd)
+            cmd, out, err, rc = self._build('/dev/null', source_path,
+                                            compile_only=True,
+                                            use_verify=use_verify)
+            expected_rc = 0 if use_verify else 1
             if rc == expected_rc:
                 return lit.Test.PASS, ""
             else:
@@ -144,14 +172,12 @@
             exec_file.close()
 
             try:
-                compile_cmd = [self.cxx_under_test, '-o', exec_path,
-                       source_path] + self.cpp_flags + self.ld_flags
-                cmd = compile_cmd
-                out, err, exitCode = self.execute_command(cmd)
-                if exitCode != 0:
+                cmd, out, err, rc = self._build(exec_path, source_path)
+                compile_cmd = cmd
+                if rc != 0:
                     report = """Command: %s\n""" % ' '.join(["'%s'" % a
                                                              for a in cmd])
-                    report += """Exit Code: %d\n""" % exitCode
+                    report += """Exit Code: %d\n""" % rc
                     if out:
                         report += """Standard Output:\n--\n%s--""" % out
                     if err:
@@ -159,21 +185,14 @@
                     report += "\n\nCompilation failed unexpectedly!"
                     return lit.Test.FAIL, report
 
-                cmd = []
-                if self.exec_env:
-                    cmd.append('env')
-                    cmd.extend('%s=%s' % (name, value)
-                               for name,value in self.exec_env.items())
-                cmd.append(exec_path)
-                if lit_config.useValgrind:
-                    cmd = lit_config.valgrindArgs + cmd
-                out, err, exitCode = self.execute_command(cmd, source_dir)
-                if exitCode != 0:
+                cmd, out, err, rc = self._run(exec_path, lit_config,
+                                              source_dir)
+                if rc != 0:
                     report = """Compiled With: %s\n""" % \
                         ' '.join(["'%s'" % a for a in compile_cmd])
                     report += """Command: %s\n""" % \
                         ' '.join(["'%s'" % a for a in cmd])
-                    report += """Exit Code: %d\n""" % exitCode
+                    report += """Exit Code: %d\n""" % rc
                     if out:
                         report += """Standard Output:\n--\n%s--""" % out
                     if err:
@@ -182,7 +201,9 @@
                     return lit.Test.FAIL, report
             finally:
                 try:
-                    os.remove(exec_path)
+                    # Note that cleanup of exec_file happens in `_clean()`. If
+                    # you override this, cleanup is your reponsibility.
+                    self._clean(exec_path)
                 except:
                     pass
         return lit.Test.PASS, ""
@@ -514,6 +535,11 @@
 # test_source_root: The root path where tests are located.
 config.test_source_root = os.path.dirname(__file__)
 
-configuration = Configuration(lit_config, config)
+cfg_variant = getattr(config, 'configuration_variant', '')
+if cfg_variant:
+    print 'Using configuration variant: %s' % cfg_variant
+
+# Construct an object of the type named `<VARIANT>Configuration`.
+configuration = globals()['%sConfiguration' % cfg_variant](lit_config, config)
 configuration.configure()
 config.test_format = configuration.get_test_format()