linux/include
chenqiwu 57e86fa16a mm: replace zero-length array with flexible-array member
The current codebase makes use of the zero-length array language extension
to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

    struct foo {
        int stuff;
        struct boo array[];
    };

By making use of the mechanism above, we will get a compiler warning in
case the flexible array does not occur last in the structure, which will
help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by this
change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied.  As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

[akpm@linux-foundation.org: fix build]
Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Baoquan He <bhe@redhat.com>
Link: http://lkml.kernel.org/r/1586599916-15456-1-git-send-email-qiwuchen55@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-04 19:06:23 -07:00
..
acpi Merge branches 'acpi-apei', 'acpi-pmic', 'acpi-video' and 'acpi-dptf' 2020-06-01 17:19:43 +02:00
asm-generic mm: remove __ARCH_HAS_5LEVEL_HACK and include/asm-generic/5level-fixup.h 2020-06-04 19:06:21 -07:00
clocksource
crypto
drm drm: remove drm specific kmap_atomic code 2020-06-04 19:06:22 -07:00
dt-bindings
keys
kunit
kvm
linux mm: replace zero-length array with flexible-array member 2020-06-04 19:06:23 -07:00
math-emu
media media updates for v5.8-rc1 2020-06-03 20:59:38 -07:00
misc
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-06-03 16:27:18 -07:00
pcmcia
ras
rdma
scsi
soc
sound
target
trace Merge branch 'akpm' (patches from Andrew) 2020-06-03 20:24:15 -07:00
uapi media updates for v5.8-rc1 2020-06-03 20:59:38 -07:00
vdso
video
xen