| Message ID | 20200508210805.GA24170@embeddedor |
|---|---|
| State | New |
| Headers | show |
| Series | firmware: qcom_scm-legacy: Replace zero-length array with flexible-array | expand |
diff --git a/drivers/firmware/qcom_scm-legacy.c b/drivers/firmware/qcom_scm-legacy.c index 8532e7c78ef7..eba6b60bfb61 100644 --- a/drivers/firmware/qcom_scm-legacy.c +++ b/drivers/firmware/qcom_scm-legacy.c @@ -56,7 +56,7 @@ struct scm_legacy_command { __le32 buf_offset; __le32 resp_hdr_offset; __le32 id; - __le32 buf[0]; + __le32 buf[]; }; /**
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") Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- drivers/firmware/qcom_scm-legacy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)