[Qemu-devel] [PATCH] slirp: Fix build with gcc 9

[Greg Kurz]

Build fails with gcc 9:

  CC      slirp/ndp_table.o
slirp/ndp_table.c: In function ‘ndp_table_add’:
slirp/ndp_table.c:31:23: error: taking address of packed member of ‘struct 
ndpentry’ may result in an unaligned pointer value 
[-Werror=address-of-packed-member]
   31 |         if (in6_equal(&ndp_table->table[i].ip_addr, &ip_addr)) {
      |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
slirp/ndp_table.c: In function ‘ndp_table_search’:
slirp/ndp_table.c:75:23: error: taking address of packed member of ‘struct 
ndpentry’ may result in an unaligned pointer value 
[-Werror=address-of-packed-member]
   75 |         if (in6_equal(&ndp_table->table[i].ip_addr, &ip_addr)) {
      |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

All members of struct ndpentry are naturally aligned. Drop the QEMU_PACKED
attribute and check there isn't unwanted padding at build time.

Signed-off-by: Greg Kurz <address@hidden>
---
 slirp/slirp.h |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/slirp/slirp.h b/slirp/slirp.h
index 752a4cd8c81c..97552962697a 100644
--- a/slirp/slirp.h
+++ b/slirp/slirp.h
@@ -106,7 +106,9 @@ bool arp_table_search(Slirp *slirp, uint32_t ip_addr,
 struct ndpentry {
     unsigned char   eth_addr[ETH_ALEN];     /* sender hardware address */
     struct in6_addr ip_addr;                /* sender IP address       */
-} SLIRP_PACKED;
+};
+
+G_STATIC_ASSERT(sizeof(struct ndpentry) == 22);
 
 #define NDP_TABLE_SIZE 16