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[PULL,3/3] slirp: Don't mark struct ipq or struct ipasfrag as packed

Message ID 20190126212010.11730-4-samuel.thibault@ens-lyon.org (mailing list archive)
State New, archived
Headers show
Series [PULL,1/3] slirp: Avoid unaligned 16bit memory access | expand

Commit Message

Samuel Thibault Jan. 26, 2019, 9:20 p.m. UTC 
From: Peter Maydell <peter.maydell@linaro.org>

There is no reason to mark the struct ipq and struct ipasfrag as
packed: they are naturally aligned anyway, and are not representing
any on-the-wire packet format.  Indeed they vary in size depending on
the size of pointers on the host system, because the 'struct qlink'
members include 'void *' fields.

Dropping the 'packed' annotation fixes clang -Waddress-of-packed-member
warnings and probably lets the compiler generate better code too.

The only thing we do care about in the layout of the struct is
that the frag_link matches up with the ipf_link of the struct
ipasfrag, as documented in the comment on that struct; assert
at build time that this is the case.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
---
 slirp/ip.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
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Patch

diff --git a/slirp/ip.h b/slirp/ip.h
index 243b6c8b24..20614f3b53 100644
--- a/slirp/ip.h
+++ b/slirp/ip.h
@@ -217,7 +217,7 @@  struct ipq {
 	uint8_t	ipq_p;			/* protocol of this fragment */
 	uint16_t	ipq_id;			/* sequence id for reassembly */
 	struct	in_addr ipq_src,ipq_dst;
-} QEMU_PACKED;
+};
 
 /*
  * Ip header, when holding a fragment.
@@ -227,7 +227,10 @@  struct ipq {
 struct	ipasfrag {
 	struct qlink ipf_link;
 	struct ip ipf_ip;
-} QEMU_PACKED;
+};
+
+QEMU_BUILD_BUG_ON(offsetof(struct ipq, frag_link) !=
+                  offsetof(struct ipasfrag, ipf_link));
 
 #define ipf_off      ipf_ip.ip_off
 #define ipf_tos      ipf_ip.ip_tos