Avoid printf %n

Index: apps/rehash.c
--- apps/rehash.c.orig
+++ apps/rehash.c
@@ -427,8 +427,9 @@ static int do_dir(const char *dirname, enum Hash h)
                     while (bit_isset(idmask, nextid))
                         nextid++;
 
-                    BIO_snprintf(buf, buflen, "%s%s%n%08x.%s%d",
-                                 dirname, pathsep, &n, bp->hash,
+                    n = BIO_snprintf(buf, buflen, "%s%s", dirname, pathsep);
+                    BIO_snprintf(&buf[n], buflen - n, "%08x.%s%d",
+                                 bp->hash,
                                  suffixes[bp->type], nextid);
                     if (verbose)
                         BIO_printf(bio_out, "link %s -> %s\n",
@@ -449,8 +450,9 @@ static int do_dir(const char *dirname, enum Hash h)
                     bit_set(idmask, nextid);
                 } else if (remove_links) {
                     /* Link to be deleted */
-                    BIO_snprintf(buf, buflen, "%s%s%n%08x.%s%d",
-                                 dirname, pathsep, &n, bp->hash,
+                    n = BIO_snprintf(buf, buflen, "%s%s", dirname, pathsep);
+                    BIO_snprintf(&buf[n], buflen - n, "%08x.%s%d",
+                                 bp->hash,
                                  suffixes[bp->type], ep->old_id);
                     if (verbose)
                         BIO_printf(bio_out, "unlink %s\n",