Align pcap_t private data on an 8-byte boundary.

It might be necessary on some platforms, and there's no portable way to
determine whether it is necessary.

diff --git a/pcap.c b/pcap.c
index 95ea26e3fdb65b682256e4bf5b48beb3753ec297..90230486744c17681b4a53f25a5be65e0f62f114 100644 (file)
--- a/pcap.c
+++ b/pcap.c
@@ -2124,14 +2124,23 @@ pcap_alloc_pcap_t(char *ebuf, size_t size)
         * plus a structure following it of size "size".  The
         * structure following it is a private data structure
         * for the routines that handle this pcap_t.
+        *
+        * The structure following it must be aligned on
+        * the appropriate alignment boundary for this platform.
+        * We align on an 8-byte boundary as that's probably what
+        * at least some platforms do, even with 32-bit integers,
+        * and because we can't be sure that some values won't
+        * require 8-byte alignment even on platforms with 32-bit
+        * integers.
         */
-       chunk = malloc(sizeof (pcap_t) + size);
+#define PCAP_T_ALIGNED_SIZE    ((sizeof(pcap_t) + 7) & ~0x7)
+       chunk = malloc(PCAP_T_ALIGNED_SIZE + size);
        if (chunk == NULL) {
                pcap_fmt_errmsg_for_errno(ebuf, PCAP_ERRBUF_SIZE,
                    errno, "malloc");
                return (NULL);
        }
-       memset(chunk, 0, sizeof (pcap_t) + size);
+       memset(chunk, 0, PCAP_T_ALIGNED_SIZE + size);
 
        /*
         * Get a pointer to the pcap_t at the beginning.
@@ -2156,7 +2165,7 @@ pcap_alloc_pcap_t(char *ebuf, size_t size)
                 * Set the pointer to the private data; that's the structure
                 * of size "size" following the pcap_t.
                 */
-               p->priv = (void *)(chunk + sizeof (pcap_t));
+               p->priv = (void *)(chunk + PCAP_T_ALIGNED_SIZE);
        }
 
        return (p);