=== modified file 'acinclude/compiler-flags.m4'
--- acinclude/compiler-flags.m4	2013-06-09 20:35:58 +0000
+++ acinclude/compiler-flags.m4	2013-06-21 13:23:52 +0000
@@ -169,8 +169,14 @@
    squid_cv_cc_option_optimize="-fast"
    squid_cv_cc_arg_pipe=""
    ;;
-  clang) 
-   squid_cv_cxx_option_werror="-Werror -Wno-error=parentheses-equality -Qunused-arguments"
+  clang)
+     squid_cv_cxx_option_werror="-Werror"
+   SQUID_CC_CHECK_ARGUMENT([squid_cv_clang_no_error_parentheses_equality],[-Werror -Wno-error=parentheses-equality])
+   SQUID_CC_CHECK_ARGUMENT([squid_cv_clang_qunused_arguments],[-Werror -Qunused-arguments])
+   if test "x$squid_cv_clang_no_error_parentheses_equality" = "xyes" \
+     -a "x$squid_cv_clang_qunused_arguments" = "xyes" ; then
+     squid_cv_cxx_option_werror="$squid_cv_cxx_option_werror -Wno-error=parentheses-equality -Qunused-arguments"
+   fi
    squid_cv_cc_option_werror="$squid_cv_cxx_option_werror" 
    squid_cv_cc_option_wall="-Wall"
    squid_cv_cc_option_optimize="-O2"