Messages in this thread | | | Date | Thu, 21 May 2020 13:32:35 -0500 | From | "Gustavo A. R. Silva" <> | Subject | Re: [PATCH] ibft: Replace zero-length array with flexible-array |
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Hi all,
Friendly ping: who can take this?
Thanks -- Gustavo
On Thu, May 07, 2020 at 01:55:44PM -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/firmware/iscsi_ibft.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/firmware/iscsi_ibft.c b/drivers/firmware/iscsi_ibft.c > index 96758b71a8db..7127a04bca19 100644 > --- a/drivers/firmware/iscsi_ibft.c > +++ b/drivers/firmware/iscsi_ibft.c > @@ -104,7 +104,7 @@ struct ibft_control { > u16 tgt0_off; > u16 nic1_off; > u16 tgt1_off; > - u16 expansion[0]; > + u16 expansion[]; > } __attribute__((__packed__)); > > struct ibft_initiator { >
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