On Thu, May 7, 2020 at 1:49 PM Gustavo A. R. Silva <gustavo...@kernel.org> 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 <gustavo...@kernel.org> > --- > include/linux/fsl/bestcomm/bestcomm.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-)
Applied for next. Thanks. Regards, Leo > > diff --git a/include/linux/fsl/bestcomm/bestcomm.h > b/include/linux/fsl/bestcomm/bestcomm.h > index a0e2e6b19b57..154e541ce57e 100644 > --- a/include/linux/fsl/bestcomm/bestcomm.h > +++ b/include/linux/fsl/bestcomm/bestcomm.h > @@ -27,7 +27,7 @@ > */ > struct bcom_bd { > u32 status; > - u32 data[0]; /* variable payload size */ > + u32 data[]; /* variable payload size */ > }; > > /* ======================================================================== > */ >