diff --git a/configure.ac b/configure.ac
index e24f41f1..f4937170 100644
--- a/configure.ac
+++ b/configure.ac
@@ -31,6 +31,30 @@ AC_ARG_WITH([pkgconfigdir], AS_HELP_STRING([--with-pkgconfigdir=DIR],
             [pkgconfigdir="$withval"], [pkgconfigdir='${libdir}/pkgconfig'])
 AC_SUBST([pkgconfigdir])
 
+dnl === TEST_AND_ADD_CFLAGS(flag)
+dnl ===   Checks whether $CC supports 'flag' and adds it to AM_CFLAGS on success.
+AC_DEFUN([TEST_AND_ADD_CFLAGS],
+         [SAVED_CFLAGS="$CFLAGS"
+          CFLAGS="-Werror $1"
+          AC_MSG_CHECKING([whether $CC supports $1])
+          dnl Note AC_LANG_PROGRAM([]) uses an old-style main definition.
+          AC_COMPILE_IFELSE([AC_LANG_SOURCE([int main(void) { return 0; }])],
+                            [AC_MSG_RESULT([yes])]
+                            [AS_VAR_APPEND([AM_CFLAGS], [" $1"])],
+                            [AC_MSG_RESULT([no])])
+          CFLAGS="$SAVED_CFLAGS"])
+TEST_AND_ADD_CFLAGS([-Wall])
+TEST_AND_ADD_CFLAGS([-Wdeclaration-after-statement])
+TEST_AND_ADD_CFLAGS([-Wextra])
+TEST_AND_ADD_CFLAGS([-Wmissing-declarations])
+TEST_AND_ADD_CFLAGS([-Wmissing-prototypes])
+TEST_AND_ADD_CFLAGS([-Wold-style-definition])
+TEST_AND_ADD_CFLAGS([-Wshadow])
+TEST_AND_ADD_CFLAGS([-Wunused-but-set-variable])
+TEST_AND_ADD_CFLAGS([-Wunused])
+TEST_AND_ADD_CFLAGS([-Wvla])
+AC_SUBST([AM_CFLAGS])
+
 dnl === CLEAR_LIBVARS([var_pfx])
 dnl ===   Clears <var_pfx>_{INCLUDES,LIBS}.
 AC_DEFUN([CLEAR_LIBVARS], [$1_INCLUDES=""; $1_LIBS=""])