On Fri, May 1, 2020 at 4:53 PM James Bottomley <jejb@xxxxxxxxxxxxx> wrote:
> On Fri, 2020-05-01 at 09:54 +0200, Arnd Bergmann wrote:
> > On Fri, May 1, 2020 at 9:48 AM John Garry <john.garry@xxxxxxxxxx>
> > wrote:
> > I found one hack that would work, but I think it's too ugly and
> > likely not well-defined either:
> >
> > struct ssp_response_iu {
> > ...
> > struct {
> > u8 dummy[0]; /* a struct must have at least one
> > non-flexible member */
>
> If gcc is now warning about zero length members, why isn't it warning
> about this one ... are unions temporarily excluded?
It does not warn about all zero-length arrays, but it does warn when you
try to access an array with an out-of-range index, and this apparently
got extended in gcc-10 to any index for zero-length arrays.
> > u8 resp_data[]; /* allowed here because it's at
> > the one of a struct */
> > };
> > u8 sense_data[];
> > } __attribute__ ((packed));
>
> Let's go back to what the standard says: we want the data beyond the
> ssp_response_iu to be addressable either as sense_data if it's an error
> return or resp_data if it's a real response. What about trying to use
> an alias attribute inside the structure ... will that work on gcc-10?
I think alias attributes only work for functions and variables, but not
for struct members.
A "#define sense_data resp_data" would obviously work, but it's
rather error-prone when other code uses the same identifiers.
Another option would be an inline helper like
static inline u8 *ssp_response_data(struct ssp_response_iu *iu)
{
return iu.resp_data;
}
Arnd
