+if test "x$visibility" = xauto ; then
+# This test checks toolchain support for several things:
+# - the -include option
+# - the attributes/pragmas used in vis.h
+# - linking code that takes the address of protected symbols
+printf "checking whether global visibility preinclude works... "
+echo 'int (*fp)(void);' > "$tmpc"
+echo 'int foo(void) { }' >> "$tmpc"
+echo 'int bar(void) { fp = foo; return foo(); }' >> "$tmpc"
+if $CC $CFLAGS_C99FSE $CPPFLAGS $CFLAGS \
+ -DSHARED -fPIC -I./src/internal -include vis.h \
+ -nostdlib -shared -Wl,-Bsymbolic-functions \
+ -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
+visibility=yes
+else
+visibility=no
+fi
+printf "%s\n" "$visibility"
+fi
+
+if test "x$visibility" = xyes ; then
+CFLAGS_AUTO="$CFLAGS_AUTO -include vis.h"
+CFLAGS_AUTO="${CFLAGS_AUTO# }"
+fi
+