On Mon, Jun 17, 2019 at 03:59:32PM +0800, Qu Wenruo wrote:
> This patchset will address the remaining warning when compiling
> btrfs-progs devel branch with GCC9.
>
> It's based on the following commit:
> commit 9a1d86a9ac7384b332db498822585a2255f7d3e6 (david/devel)
> Author: David Sterba <dsterba@xxxxxxxx>
> Date: Thu Jun 13 20:45:49 2019 +0200
>
> btrfs-progs: build: disable -Waddress-of-packed-member by default
>
>
> Please note that the 2nd patch mostly replace commit 691656abdc9a
> ("btrfs-progs: fix gcc9 warning and potentially unaligned access to dev stats") by
> backporing kernel btrfs_dev_stats_value() to btrfs-progs.
> Thus the original fix can be removed.
Yeah, the backport is better, patch replaced.
> The remaining warning is -Warray-boundary, but that one looks pretty
> strange. The code looks good, and I backported an easy version:
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <stddef.h>
>
> struct test_struct {
> long long off_0_7;
> int offset_8_11;
> unsigned char offset_12_12;
> } __attribute__ ((packed));
>
> void reset_values(struct test_struct *ptr)
> {
> memset(&ptr->offset_8_11, 0, sizeof(struct test_struct) - offsetof(struct test_struct, offset_8_11));
> }
>
> int main()
> {
> struct test_struct my_struct = { 0xffff, 0xff, 0xff};
>
> printf("struct=0x%llx start=0x%llx len=0x%x\n",
> &my_struct, &my_struct.offset_8_11, sizeof(struct test_struct) - offsetof(struct test_struct, offset_8_11));
> reset_values(&my_struct);
> printf("0x%lx 0x%x 0x%x\n", my_struct.off_0_7, my_struct.offset_8_11, my_struct.offset_12_12);
> return 0;
> }
>
> Which doesn't reproduce the warning.
> Thus looks like a false warning and a bug in gcc.
>
> Qu Wenruo (4):
> btrfs-progs: constify extent buffer reader
> btrfs-progs: Fix -Waddress-of-packed-member warning in
> btrfs_dev_stats_values callers
> btrfs-progs: Remove unnecessary fallthrough attribute in
> test_num_disk_vs_raid()
> btrfs-progs: Fix Wformat-overflow warning in cmds-receive.c
1-4 applied, thanks.
