Messages in this thread | | | Subject | Re: [PATCH] auxdisplay: charlcd: replace zero-length array with flexible-array member | From | "Gustavo A. R. Silva" <> | Date | Thu, 13 Feb 2020 00:13:41 -0600 |
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Hi Miguel,
On 2/12/20 14:49, Miguel Ojeda wrote: > Hi Gustavo, > > On Wed, Feb 12, 2020 at 8:49 PM Gustavo A. R. Silva > <gustavo@embeddedor.com> 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. > > s:inadvertenly:inadvertently: >
Thanks for this.
>> 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> > > I saw the discussion regarding this -- thanks! Do you want me to > handle this or will you push everything centrally? If the latter, have > my >
Please, go ahead and handle it.
> Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> >
Thanks -- Gustavo
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