Messages in this thread | | | Subject | Re: [PATCH] gcov: gcc_4_7: Replace zero-length array with flexible-array member | From | Peter Oberparleiter <> | Date | Wed, 26 Feb 2020 14:38:40 +0100 |
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On 13.02.2020 16:22, 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>
Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Andrew, could you pick this patch up?
> --- > kernel/gcov/gcc_4_7.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c > index ec37563674d6..908fdf5098c3 100644 > --- a/kernel/gcov/gcc_4_7.c > +++ b/kernel/gcov/gcc_4_7.c > @@ -68,7 +68,7 @@ struct gcov_fn_info { > unsigned int ident; > unsigned int lineno_checksum; > unsigned int cfg_checksum; > - struct gcov_ctr_info ctrs[0]; > + struct gcov_ctr_info ctrs[]; > }; > > /** >
-- Peter Oberparleiter Linux on Z Development - IBM Germany
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