Detect closefrom(2) support

build/autotools/configure.ac

@@ -222,7 +222,7 @@ AC_CHECK_FUNCS([getrusage getpassphrase posix_madvise madvise])
 AC_CHECK_FUNCS([memmem random snprintf srandom gettime])
 #checkpoint
 AC_CACHE_SAVE
-AC_CHECK_FUNCS([vsnprintf prctl procctl])
+AC_CHECK_FUNCS([vsnprintf prctl procctl closefrom])
 
 #autoscan suggested this....
 #These are recommended by autoscan, but no code supports it currently

configure

@@ -8290,7 +8290,7 @@ $as_echo "$as_me: not updating unwritable cache $cache_file" >&6;}
   fi
 fi
 rm -f confcache
-for ac_func in vsnprintf prctl procctl
+for ac_func in vsnprintf prctl procctl closefrom
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 ac_fn_cxx_check_func "$LINENO" "$ac_func" "$as_ac_var"

src/config.h.in

@@ -22,6 +22,9 @@
 /* Define to 1 if you have the <arpa/inet.h> header file. */
 #undef HAVE_ARPA_INET_H
 
+/* Define to 1 if you have the `closefrom' function. */
+#undef HAVE_CLOSEFROM
+
 /* define if the compiler supports basic C++11 syntax */
 #undef HAVE_CXX11