On 8/12/19 7:53 PM, Jens Axboe wrote:
On 8/12/19 8:01 PM, Bart Van Assche wrote:
Instead of declaring the whole structure packed, only declare non-aligned
members packed. This patch is an alternative way to fix the following gcc 9
compiler warnings:
eta.c: In function 'calc_thread_status':
eta.c:510:7: error: taking address of packed member of 'struct jobs_eta' may result in an unaligned pointer value [-Werror=address-of-packed-member]
510 | je->rate);
| ~~^~~~~~
eta.c:522:66: error: taking address of packed member of 'struct jobs_eta' may result in an unaligned pointer value [-Werror=address-of-packed-member]
522 | calc_rate(unified_rw_rep, disp_time, io_bytes, disp_io_bytes, je->rate);
| ~~^~~~~~
eta.c:523:64: error: taking address of packed member of 'struct jobs_eta' may result in an unaligned pointer value [-Werror=address-of-packed-member]
523 | calc_iops(unified_rw_rep, disp_time, io_iops, disp_io_iops, je->iops);
|
This seems fragile. Not that we change the struct all the time, or even often,
but it'd be easy to add members and end up with different layout on 32-bit
vs 64-bit.
How do we improve on that?
Hi Jens,
Do you agree that the "BUILD_BUG_ON(sizeof(struct jobs_eta) != 160)"
statement added by the previous patch should catch such differences? 160
bytes namely is the size of an entirely packed jobs_eta structure.
Thanks,
Bart.
