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author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 14:06:38 -0500 |
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committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2020-05-15 18:20:49 +0200 |
commit | 9361797c7696874a1136442b5ee69c62b0e54738 (patch) | |
tree | 50f0c4809d2ff44e906a9f37485d2a8d8c52e3b8 /drivers/pnp | |
parent | 2ef96a5bb12be62ef75b5828c0aab838ebb29cb8 (diff) | |
download | lwn-9361797c7696874a1136442b5ee69c62b0e54738.tar.gz lwn-9361797c7696874a1136442b5ee69c62b0e54738.zip |
PNPBIOS: 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 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/pnp')
-rw-r--r-- | drivers/pnp/pnpbios/pnpbios.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/pnp/pnpbios/pnpbios.h b/drivers/pnp/pnpbios/pnpbios.h index 37acb8378f39..2ce739ff9c1a 100644 --- a/drivers/pnp/pnpbios/pnpbios.h +++ b/drivers/pnp/pnpbios/pnpbios.h @@ -107,7 +107,7 @@ struct pnp_bios_node { __u32 eisa_id; __u8 type_code[3]; __u16 flags; - __u8 data[0]; + __u8 data[]; }; #pragma pack() |