linux/arch/um
Gustavo A. R. Silva f6e8c47439 um: virtio: Replace zero-length array with flexible-array
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]

sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.

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")

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Richard Weinberger <richard@nod.at>
2020-06-02 22:38:00 +02:00
..
configs um: Cleanup CONFIG_IOSCHED_CFQ 2020-03-29 23:15:22 +02:00
drivers um: virtio: Replace zero-length array with flexible-array 2020-06-02 22:38:00 +02:00
include um: Fix xor.h include 2020-04-29 21:21:51 +02:00
kernel um: syscall.c: include <asm/unistd.h> 2020-04-29 21:22:04 +02:00
os-Linux um: Use fdatasync() when mapping the UBD FSYNC command 2020-06-02 22:37:55 +02:00
scripts License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
Kconfig um: Make CONFIG_STATIC_LINK actually static 2020-03-29 23:51:24 +02:00
Kconfig.debug um: Make GCOV depend on !KCOV 2018-12-27 22:48:19 +01:00
Makefile um: ensure make ARCH=um mrproper removes arch/$(SUBARCH)/include/generated/ 2020-04-23 10:50:26 +09:00
Makefile-os-Linux
Makefile-skas