avoid memcpy(malloc(0), ..., 0), which is not portable.

ok florian@

diff --git a/lib/libc/asr/getrrsetbyname_async.c b/lib/libc/asr/getrrsetbyname_async.c
index 43e6cfe..6fd2e37 100644 (file)
--- a/lib/libc/asr/getrrsetbyname_async.c
+++ b/lib/libc/asr/getrrsetbyname_async.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: getrrsetbyname_async.c,v 1.13 2023/03/15 22:12:00 millert Exp $       */
+/*     $OpenBSD: getrrsetbyname_async.c,v 1.14 2024/05/07 23:40:53 djm Exp $   */
 /*
  * Copyright (c) 2012 Eric Faurot <eric@openbsd.org>
  *
@@ -170,7 +170,7 @@ getrrsetbyname_async_run(struct asr_query *as, struct asr_result *ar)
 
 /* The rest of this file is taken from the original implementation. */
 
-/* $OpenBSD: getrrsetbyname_async.c,v 1.13 2023/03/15 22:12:00 millert Exp $ */
+/* $OpenBSD: getrrsetbyname_async.c,v 1.14 2024/05/07 23:40:53 djm Exp $ */
 
 /*
  * Copyright (c) 2001 Jakob Schlyter. All rights reserved.
@@ -334,13 +334,14 @@ get_response(struct asr_result *ar, const char *pkt, int pktlen)
 
                if (rdata) {
                        rdata->rdi_length = rr->size;
-                       rdata->rdi_data   = malloc(rr->size);
-
-                       if (rdata->rdi_data == NULL) {
-                               ar->ar_rrset_errno = ERRSET_NOMEMORY;
-                               goto fail;
+                       if (rr->size != 0) {
+                               rdata->rdi_data = malloc(rr->size);
+                               if (rdata->rdi_data == NULL) {
+                                       ar->ar_rrset_errno = ERRSET_NOMEMORY;
+                                       goto fail;
+                               }
+                               memcpy(rdata->rdi_data, rr->rdata, rr->size);
                        }
-                       memcpy(rdata->rdi_data, rr->rdata, rr->size);
                }
        }
        free_dns_response(response);
@@ -552,12 +553,13 @@ parse_dns_rrsection(const u_char *answer, int size, const u_char **cp,
 
                /* rdata itself */
                NEED(curr->size);
-               curr->rdata = malloc(curr->size);
-               if (curr->rdata == NULL) {
-                       free_dns_rr(head);
-                       return (NULL);
+               if (curr->size != 0) {
+                       if ((curr->rdata = malloc(curr->size)) == NULL) {
+                               free_dns_rr(head);
+                               return (NULL);
+                       }
+                       memcpy(curr->rdata, *cp, curr->size);
                }
-               memcpy(curr->rdata, *cp, curr->size);
                *cp += curr->size;
        }
 #undef NEED