Messages in this thread | | | Date | Mon, 16 Mar 2020 15:57:47 +0100 | From | Jan Kara <> | Subject | Re: [PATCH][next] udf: udf_sb.h: Replace zero-length array with flexible-array member |
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On Mon 09-03-20 15:27:15, 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] > > 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@embeddedor.com>
Thanks. I've added the patch to my tree.
> --- > fs/udf/udf_sb.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/udf/udf_sb.h b/fs/udf/udf_sb.h > index 3d83be54c474..65280ae009e0 100644 > --- a/fs/udf/udf_sb.h > +++ b/fs/udf/udf_sb.h > @@ -83,7 +83,7 @@ struct udf_virtual_data { > struct udf_bitmap { > __u32 s_extPosition; > int s_nr_groups; > - struct buffer_head *s_block_bitmap[0]; > + struct buffer_head *s_block_bitmap[]; > }; > > struct udf_part_map { > -- > 2.25.0 > -- Jan Kara <jack@suse.com> SUSE Labs, CR
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