--- configure.ac.orig	2016-12-26 20:59:49.000000000 +0000
+++ configure.ac	2017-07-04 16:35:44.818612000 +0000
@@ -18,14 +18,23 @@
 
 AC_SUBST(dunelegacydatadir)
 
-dnl Some flags for gcc
-CXXFLAGS="-std=c++11 -pthread -fPIC -O3 -pipe -pedantic -Wall -Wextra -Wno-unused-parameter -Wno-shift-negative-value -DNDEBUG"
-CFLAGS="-std=c99 -pthread -fPIC -O3 -pipe -pedantic -Wall -Wextra -Wno-unused-parameter -Wno-shift-negative-value -DNDEBUG"
-dnl Additional flags: -Wconversion -Wno-sign-conversion -Wlogical-op
+AC_MSG_CHECKING([if compiling with clang])
 
-dnl Some flags for clang
-dnl CXXFLAGS="-std=c++11 -O3 -pipe -pedantic -Weverything -Wno-sign-conversion -Wno-conversion -Wno-shadow -Wno-missing-noreturn -Wno-padded -Wno-packed -Wno-weak-vtables -Wno-c++11-narrowing -Wno-cast-align -Wno-unreachable-code -Wno-missing-prototypes -Wno-float-equal -Wno-global-constructors -Wno-exit-time-destructors -Wno-format-nonliteral -Wno-unused-macros -Wreserved-id-macro -Wextra -Wno-unused-parameter -Wno-narrowing"
+AC_COMPILE_IFELSE(
+[AC_LANG_PROGRAM([], [[
+#ifndef __clang__
+       not clang
+#endif
+]])],
+[CLANG=yes], [CLANG=no])
 
+AC_MSG_RESULT([$CLANG])
+
+if test "x$CLANG" = xyes; then
+  CXXFLAGS="-std=c++11 -O3 -pipe -pedantic -Weverything -Wno-sign-conversion -Wno-conversion -Wno-shadow -Wno-missing-noreturn -Wno-padded -Wno-packed -Wno-weak-vtables -Wno-c++11-narrowing -Wno-cast-align -Wno-unreachable-code -Wno-missing-prototypes -Wno-float-equal -Wno-global-constructors -Wno-exit-time-destructors -Wno-format-nonliteral -Wno-unused-macros -Wextra -Wno-unused-parameter"
+else
+  CXXFLAGS="-O3 -pipe -pedantic -Wall -Wextra -Wno-unused-parameter -DNDEBUG"
+fi
 
 AC_ARG_ENABLE([debug],
             [AS_HELP_STRING([--enable-debug],