-if test "x$warnings" = xyes ; then
-tryflag CFLAGS_AUTO -Wall
-tryflag CFLAGS_AUTO -Wno-parentheses
-tryflag CFLAGS_AUTO -Wno-uninitialized
-tryflag CFLAGS_AUTO -Wno-missing-braces
-tryflag CFLAGS_AUTO -Wno-unused-value
-tryflag CFLAGS_AUTO -Wno-unused-but-set-variable
-tryflag CFLAGS_AUTO -Wno-unknown-pragmas
-tryflag CFLAGS_AUTO -Wno-pointer-to-int-cast
-fi
-
-if test "x$visibility" = xauto ; then
-# This test checks toolchain support for several things:
-# - the -include option
-# - the attributes/pragmas used in vis.h
-# - linking code that takes the address of protected symbols
-# - gcc 3.x bug that wrongly claims declarations mismatch
-printf "checking whether global visibility preinclude works... "
-cat > "$tmpc" <<EOF
-__attribute__((__visibility__("default")))
-extern struct a *const x;
-typedef struct a b;
-extern b *const x;
-b *const x;
-int (*fp)(void);
-int foo(void) { }
-int bar(void) { fp = foo; return foo(); }
-EOF
-if $CC $CFLAGS_C99FSE $CPPFLAGS $CFLAGS \
- -DSHARED -fPIC -I$srcdir/src/internal -include vis.h \
- -nostdlib -shared -Wl,-Bsymbolic-functions \
- -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
-visibility=yes
-else
-visibility=no
-fi
-printf "%s\n" "$visibility"
-fi
+#
+# GCC ignores unused arguements by default, but Clang needs this extra
+# parameter to stop printing warnings about LDFLAGS passed during
+# compiling stage and CFLAGS passed during linking stage.
+#
+test "$cc_family" = clang && tryflag CFLAGS_AUTO -Qunused-arguments