Messages in this thread | | | From | Adam Thomson <> | Subject | RE: [PATCH] regulator: da9062: Replace zero-length array with flexible-array member | Date | Wed, 12 Feb 2020 14:55:07 +0000 |
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On 12 February 2020 14:29, Gustavo A. R. Silva wrote:
> On 2/12/20 05:12, Adam Thomson wrote: > > On 11 February 2020 23:46, 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 > >> inadvertenly introduced[3] to the codebase from now on. > >> > >> 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> > >> --- > >> drivers/regulator/da9062-regulator.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/drivers/regulator/da9062-regulator.c b/drivers/regulator/da9062- > >> regulator.c > >> index b064d8a19d4c..c3b6ba9bafdf 100644 > >> --- a/drivers/regulator/da9062-regulator.c > >> +++ b/drivers/regulator/da9062-regulator.c > >> @@ -86,7 +86,7 @@ struct da9062_regulators { > >> int irq_ldo_lim; > >> unsigned n_regulators; > >> /* Array size to be defined during init. Keep at end. */ > >> - struct da9062_regulator regulator[0]; > >> + struct da9062_regulator regulator[]; > > > > I don't think is the correct change here for this driver. In the probe > > 'struct_size()' is used to determine the actual size requested from 'malloc()' > > when allocating memory for this structure. It's not statically initialised. > > Your change will break that code I believe. > > > > 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] > > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
Yeah, ok misinterpreted the descriptions in there. In which case:
Acked-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
> > Thanks > -- > Gustavo
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