linux/sound/firewire/fireworks
Gustavo A. R. Silva 89ebe49aaa ALSA: fireworks: 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>
Acked-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20200507185245.GA14270@embeddedor
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2020-05-08 09:41:30 +02:00
..
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
fireworks.c ALSA: firewire: use KBUILD_MODNAME for struct driver.name instead of string 2020-03-06 15:54:03 +01:00
fireworks.h ALSA: fireworks: Replace zero-length array with flexible-array 2020-05-08 09:41:30 +02:00
fireworks_command.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 345 2019-06-05 17:37:08 +02:00
fireworks_hwdep.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 345 2019-06-05 17:37:08 +02:00
fireworks_midi.c ALSA: fireworks: share PCM buffer size for both direction 2019-10-18 04:35:44 +02:00
fireworks_pcm.c ALSA: firewire: Drop superfluous ioctl PCM ops 2019-12-11 07:25:27 +01:00
fireworks_proc.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 345 2019-06-05 17:37:08 +02:00
fireworks_stream.c ALSA: firewire-lib: postpone to start IR context 2019-10-19 09:18:27 +02:00
fireworks_transaction.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 345 2019-06-05 17:37:08 +02:00