On Wed, Aug 15, 2012 at 05:59:26PM +0200, Stefan Weil wrote: > Am 15.08.2012 16:16, schrieb Stefan Hajnoczi: > >On Fri, Aug 10, 2012 at 10:03:27PM +0200, Stefan Weil wrote: > >>QEMU_PACKED results in a MinGW compiler warning when it is > >>used for single structure elements: > >> > >>warning: 'gcc_struct' attribute ignored > >> > >>Using QEMU_PACKED for the whole structure avoids the compiler warning > >>without changing the memory layout. > >Quick link for other reviewers: > >http://gcc.gnu.org/onlinedocs/gcc-4.7.1/gcc/Type-Attributes.html#Type-Attributes > > > >>Signed-off-by: Stefan Weil <s...@weilnetz.de> > >>--- > >> hw/srp.h | 8 ++++---- > >> 1 files changed, 4 insertions(+), 4 deletions(-) > >> > >>diff --git a/hw/srp.h b/hw/srp.h > >>index 3009bd5..5e0cad5 100644 > >>--- a/hw/srp.h > >>+++ b/hw/srp.h > >>@@ -177,13 +177,13 @@ struct srp_tsk_mgmt { > >> uint8_t reserved1[6]; > >> uint64_t tag; > >> uint8_t reserved2[4]; > >>- uint64_t lun QEMU_PACKED; > >>+ uint64_t lun; > >> uint8_t reserved3[2]; > >> uint8_t tsk_mgmt_func; > >> uint8_t reserved4; > >> uint64_t task_tag; > >> uint8_t reserved5[8]; > >>-}; > >>+} QEMU_PACKED; > >Here I actually see a difference for the uint64_t task_tag field. > >Previously it was not packed, now it is packed and because it has 4 * > >uint8_t before it there will be a difference in layout. > > > >Looking at how QEMU accesses srp_tsk_mgmt, I think we're safe because we > >never actually access task_tag? > > > >Ben: Any thoughts on this patch? > > > >Stefan > > 4 * uint8_t + 4 bytes from the packed lun, so there is no change > for task_tag, it's always on a 8 byte boundary!
Ah, yes, I see it now! Glad we're switching to struct-level packing :). Stefan