On Mon, Feb 1, 2021 at 2:48 PM Theodore Ts'o <tytso@xxxxxxx> wrote:
>
> On Mon, Feb 01, 2021 at 07:05:11PM -0300, Vinicius Tinti wrote:
> >
> > The goal is to try to detect real bugs. In this instance specifically I
> > suggested to remove the "if (0) {...}" because it sounded like an
> > unused code.
> >
> > If it is useful it is fine to keep.
>
> The trick was that it was unused code, but it was pretty obviously
> deliberate, which should have implied that at some point, it was
> considered useful. :-)
>
> It was the fact that you were so determined to find a way to suppress
> the warning, suggesting multiple tactics, which made me wonder.... why
> were you going through so much effort to silence the warning if the
> goal was *not* to turn it on unconditionally everywhere?
Because a maintainer might say "oh, I meant to turn that back on years
ago" or "that should not have been committed!" Hasn't happened yet,
doesn't mean it's impossible. Vinicius asked how he can help. I said
"go see if any instances of this warning are that case."
>
> I suspect the much more useful thing to consider is how can we suggest
> hueristics to the Clang folks to make the warning more helpful. For
> example, Coverity will warn about the following:
>
> void test_func(unsigned int arg)
> {
> if (arg < 0) {
> printf("Hello, world\n")
> }
> }
Put that code in in godbolt.org (https://godbolt.org/z/E7KK9T) and
you'll see that both compilers already warn here on -Wextra (via
-Wtautological-unsigned-zero-compare in clang or -Wtype-limits in
GCC).
clang:
warning: result of comparison of unsigned expression < 0 is always
false [-Wtautological-unsigned-zero-compare]
if (arg < 0) {
~~~ ^ ~
gcc:
warning: comparison of unsigned expression in '< 0' is always false
[-Wtype-limits]
3 | if (arg < 0) {
| ^
>
> P.S. If anyone wants to file a feature request bug with the Clang
> developers, feel free. :-)
--
Thanks,
~Nick Desaulniers
