enable system arc4random on FreeBSD 12+

1 files changed, 9 insertions, 3 deletions

diff --git a/m4/check-os-options.m4 b/m4/check-os-options.m4
index bd38938..c73709d 100644
--- a/m4/check-os-options.m4
+++ b/m4/check-os-options.m4
@@ -61,9 +61,15 @@ char buf[1]; getentropy(buf, 1);
         *freebsd*)
                 HOST_OS=freebsd
                 HOST_ABI=elf
-                # fork detection missing, weak seed on failure
-                # https://svnweb.freebsd.org/base/head/lib/libc/gen/arc4random.c?revision=268642&view=markup
-                USE_BUILTIN_ARC4RANDOM=yes
+                AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+#include <sys/param.h>
+#if __FreeBSD_version < 1200000
+        undefined
+#endif
+                       ]], [[]])],
+                       [ USE_BUILTIN_ARC4RANDOM=no ],
+                       [ USE_BUILTIN_ARC4RANDOM=yes ]
+                )
                 AC_SUBST([PROG_LDADD], ['-lthr'])
                 ;;
         *hpux*)