On Wed, Feb 23, 2022 at 12:25 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
>
> I looked at the gcc documentation for this flag, and it tells me that
> it's default-enabled for std=c99 or higher. Turning it on for --std=gnu89
> shows the same warning, so at least it doesn't sound like the actual
> behavior changed, only the warning output. clang does not warn
> for this code at all, regardless of the --std= flag.
Ok, so we should be able to basically convert '--std=gnu89' into
'--std=gnu11 -Wno-shift-negative-value' with no expected change of
behavior.
Of course, maybe we need to make -Wno-shift-negative-value be
conditional on the compiler supporting it in the first place?
I really would love to finally move forward on this, considering that
it's been brewing for many many years.
I think the loop iterators are the biggest user-visible thing, but
there might be others.
And some googling seems to show that the reason for
-Wshift-negative-value is that with C99 the semantics changed for
targets that weren't two's complement. We *really* don't care.
Of course, the C standard being the bunch of incompetents they are,
they in the process apparently made left-shifts undefined (rather than
implementation-defined). Christ, they keep on making the same mistakes
over and over. What was the definition of insanity again?
Linus
