The C standard says nothing about accesses via lvalue expressions with volatile types

src/libsodium/sodium/utils.c

@@ -69,12 +69,8 @@ sodium_memzero(void * const pnt, const size_t len)
     memset(pnt, 0, len);
     __sodium_dummy_symbol_to_prevent_lto(pnt, len);
 #else
-    volatile unsigned char *pnt_ = (volatile unsigned char *) pnt;
-    size_t                     i = (size_t) 0U;
-
-    while (i < len) {
-        pnt_[i++] = 0U;
-    }
+    static void * (* const volatile memset_ptr)(void *, int, size_t) = memset;
+    memset_ptr(pnt, 0, len);
 #endif
 }