On Wed, May 13, 2020 at 05:03:43PM +0200, Johan Hovold wrote:
On Thu, May 07, 2020 at 01:53:18PM -0500, Gustavo A. R. Silva wrote:
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
drivers/greybus/arpc.h | 2 - include/linux/greybus/greybus_protocols.h | 44 +++++++++++++++---------------
I noticed Greg just applied this one to his -testing branch, but do we really want this in greybus_protocols.h, which is meant to be shared with the firmware side? Perhaps not an issue, just figured I'd point this out.
Why not, it should be the same thing, right? No logic has changed that I see.
thanks,
greg k-h