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i3c: master: Replace zero-length array with flexible-array member

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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 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-i3c/20200227131307.GA24935@embeddedor
This commit is contained in:
Gustavo A. R. Silva 2020-02-27 07:13:07 -06:00 committed by Boris Brezillon
parent 65ec1d0ddf
commit cd851485ef
2 changed files with 2 additions and 2 deletions
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2
drivers/i3c/master/dw-i3c-master.c
View File

@ -221,7 +221,7 @@ struct dw_i3c_xfer {
struct completion comp;
int ret;
unsigned int ncmds;
struct dw_i3c_cmd cmds[0];
struct dw_i3c_cmd cmds[];
};
struct dw_i3c_master {

2
drivers/i3c/master/i3c-master-cdns.c
View File

@ -388,7 +388,7 @@ struct cdns_i3c_xfer {
struct completion comp;
int ret;
unsigned int ncmds;
struct cdns_i3c_cmd cmds[0];
struct cdns_i3c_cmd cmds[];
};
struct cdns_i3c_data {