Messages in this thread | | | Subject | Re: [PATCH][next] pnpbios: pnpbios.h: Replace zero-length array with flexible-array member | From | "Rafael J. Wysocki" <> | Date | Tue, 24 Mar 2020 17:13:50 +0100 |
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On 3/21/2020 12:18 AM, 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> > --- > drivers/pnp/pnpbios/pnpbios.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pnp/pnpbios/pnpbios.h b/drivers/pnp/pnpbios/pnpbios.h > index 37acb8378f39..2ce739ff9c1a 100644 > --- a/drivers/pnp/pnpbios/pnpbios.h > +++ b/drivers/pnp/pnpbios/pnpbios.h > @@ -107,7 +107,7 @@ struct pnp_bios_node { > __u32 eisa_id; > __u8 type_code[3]; > __u16 flags; > - __u8 data[0]; > + __u8 data[]; > }; > #pragma pack() >
Please resend this with a CC to linux-acpi, thanks!
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