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| author | Gustavo A. R. Silva <gustavo@embeddedor.com> | 2020-02-26 16:31:25 -0600 |
|---|---|---|
| committer | Ulf Hansson <ulf.hansson@linaro.org> | 2020-03-24 14:39:45 +0100 |
| commit | 1a91a36aba9c232c73e4a5fce038147f5d29e566 (patch) | |
| tree | 556ba35f35e808f13f5f51cc08f47c0a2b2b5d2c /include/linux/mmc | |
| parent | ea21e9b2b33fd06c131415cc66ca5499ab2aef5f (diff) | |
| download | lwn-1a91a36aba9c232c73e4a5fce038147f5d29e566.tar.gz lwn-1a91a36aba9c232c73e4a5fce038147f5d29e566.zip | |
mmc: 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 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20200226223125.GA20630@embeddedor
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Diffstat (limited to 'include/linux/mmc')
| -rw-r--r-- | include/linux/mmc/host.h | 2 | ||||
| -rw-r--r-- | include/linux/mmc/sdio_func.h | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h index f5db24a6a860..c318fb5b6a94 100644 --- a/include/linux/mmc/host.h +++ b/include/linux/mmc/host.h @@ -468,7 +468,7 @@ struct mmc_host { /* Host Software Queue support */ bool hsq_enabled; - unsigned long private[0] ____cacheline_aligned; + unsigned long private[] ____cacheline_aligned; }; struct device_node; diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h index 5a177f7a83c3..fa2aaab5e57a 100644 --- a/include/linux/mmc/sdio_func.h +++ b/include/linux/mmc/sdio_func.h @@ -25,7 +25,7 @@ struct sdio_func_tuple { struct sdio_func_tuple *next; unsigned char code; unsigned char size; - unsigned char data[0]; + unsigned char data[]; }; /* |