Use explicit_bzero if available

configure.ac

@@ -355,7 +355,7 @@ AS_IF([test "x$EMSCRIPTEN" = "x"],[
   AC_CHECK_FUNCS([memset_s])
 ])
 AC_CHECK_FUNCS([mlock VirtualLock])
-AC_CHECK_FUNCS([SecureZeroMemory posix_memalign])
+AC_CHECK_FUNCS([SecureZeroMemory explicit_bzero posix_memalign])
 
 AC_SUBST([LIBTOOL_EXTRA_FLAGS])
 

src/libsodium/sodium/utils.c

@@ -28,6 +28,8 @@ sodium_memzero(void * const pnt, const size_t len)
     if (memset_s(pnt, (rsize_t) len, 0, (rsize_t) len) != 0) {
         abort();
     }
+#elif defined(HAVE_EXPLICIT_BZERO)
+    explicit_bzero(pnt, len);
 #else
     volatile unsigned char *pnt_ = (volatile unsigned char *) pnt;
     size_t                     i = (size_t) 0U;