Copied from https://github.com/ansemjo/tinyssh-convert/blob/9028c16d99c6ab36aa3e51ac4f3c0b505ebfdff5/utilities.h
--- bounce.h
+++ bounce.h
@@ -292,3 +292,7 @@ static inline void base64(char *dst, const byte *src, size_t len) {
 	}
 	dst[i] = '\0';
 }
+
+/* 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
@@ -51,8 +51,7 @@ case "$(uname)" in
 		defvar OPENSSL_BIN openssl exec_prefix /bin/openssl
 		;;
 	(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))'"
 		ldadd crypt ''
 		config libtls
 		defvar OPENSSL_BIN openssl exec_prefix /bin/openssl