linux/sound/soc/intel/atom
Gustavo A. R. Silva 936b9df7a5
ASoC: Intel: Skylake: 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: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lore.kernel.org/r/20200511174647.GA17318@embeddedor
Signed-off-by: Mark Brown <broonie@kernel.org>
2020-05-12 17:14:33 +01:00
..
sst ASoC: SOF/Intel: clarify SPDX license with GPL-2.0-only 2020-05-01 17:45:24 +01:00
Makefile ASoC: SOF/Intel: clarify SPDX license with GPL-2.0-only 2020-05-01 17:45:24 +01:00
sst-atom-controls.c ASoC: Intel: atom: Check drv->lock is locked in sst_fill_and_send_cmd_unlocked 2020-04-03 14:39:57 +01:00
sst-atom-controls.h ASoC: Intel: Skylake: Replace zero-length array with flexible-array 2020-05-12 17:14:33 +01:00
sst-mfld-dsp.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 285 2019-06-05 17:36:37 +02:00
sst-mfld-platform-compress.c ASoC: intel: atom: use snd_compress_ops 2020-04-21 19:01:58 +01:00
sst-mfld-platform-pcm.c ASoC: intel: atom: use snd_compress_ops 2020-04-21 19:01:58 +01:00
sst-mfld-platform.h ASoC: intel: atom: use snd_compress_ops 2020-04-21 19:01:58 +01:00