+# AIX declares sig_atomic_t to already include volatile, and C89 compilers
+# then choke on 'volatile sig_atomic_t'. C99 requires that it compile.
+ AC_CHECK_TYPE([volatile sig_atomic_t], [],
+ [HAVE_TYPE_VOLATILE_SIG_ATOMIC_T=0], [[
+#include <signal.h>
+ ]])
+ AC_REQUIRE([AC_TYPE_UID_T])
+
+ dnl Check for declarations of anything we want to poison if the
+ dnl corresponding gnulib module is not in use.
+ gl_WARN_ON_USE_PREPARE([[#include <signal.h>
+ ]], [sigaction sigaddset sigdelset sigemptyset sigfillset sigismember
+ sigpending sigprocmask])