Copied from https://github.com/ansemjo/tinyssh-convert/blob/9028c16d99c6ab36aa3e51ac4f3c0b505ebfdff5/utilities.h
--- chat.h
+++ chat.h
@@ -460,3 +460,7 @@ int getopt_config(
 	int argc, char *const *argv,
 	const char *optstring, const struct option *longopts, int *longindex
 );
+
+/* volatile memset to try & avoid optmising it away */
+static void * (* const volatile volatile_memset)(void *, int, size_t) = memset;
+#define memzero(ptr, size) volatile_memset(ptr, 0, size)
--- configure
+++ configure
@@ -49,8 +49,7 @@ case "$(uname)" in
 		echo 'OBJS += compat_readpassphrase.o'
 		;;
 	(Darwin)
-		cflags -D__STDC_WANT_LIB_EXT1__=1
-		cflags "-D'explicit_bzero(b,l)=memset_s((b),(l),0,(l))'"
+		cflags "-D'explicit_bzero(b,l)=memzero((b),(l))'"
 		config libtls ncursesw
 		defvar OPENSSL_BIN openssl exec_prefix /bin/openssl
 		;;