Messages in this thread | | | From | Bill Wendling <> | Date | Mon, 26 Jul 2021 23:15:52 -0700 | Subject | Re: [PATCH v2 1/3] base: mark 'no_warn' as unused |
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On Mon, Jul 26, 2021 at 10:27 PM Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > On Mon, Jul 26, 2021 at 01:47:33PM -0700, Nathan Chancellor wrote: > > + Greg and Rafael as the maintainer and reviewer of drivers/base/module.c > > respectively, drop everyone else. > > Odd no one cc:ed us originally, I guess they didn't want the patch ever > merged? :( > > > > > Original post: > > > > https://lore.kernel.org/r/20210726201924.3202278-2-morbo@google.com/ > > > > On 7/26/2021 1:19 PM, 'Bill Wendling' via Clang Built Linux wrote: > > > Fix the following build warning: > > > > > > drivers/base/module.c:36:6: error: variable 'no_warn' set but not used [-Werror,-Wunused-but-set-variable] > > > int no_warn; > > That's not going to be a good warning to ever have the kernel use due to > how lots of hardware works (i.e. we need to do a read after a write but > we can throw the read away as it does not matter). > > > > > > > > This variable is used to remove another warning, but causes a warning > > > itself. Mark it as 'unused' to avoid that. > > > > > > Signed-off-by: Bill Wendling <morbo@google.com> > > > > Even though they evaluate to the same thing, it might be worth using > > "__always_unused" here because it is :) > > But it is not unused, the value is written into it. > I believe that only matters if the variable is marked "volatile". Otherwise, the variable itself is never used. A "variable that's written to but not read from," in fact, is the whole reason for the warning.
> So this isn't ok, sometimes we want to write to variables but never care > about the value, that does not mean the compiler should complain about > it. > Typically, if you don't care about the return value, you simply don't assign it to a variable (cf. printf). However, the functions that assign to "no_warn" have the "warn_unused_result" attribute. The fact that the variable is named "no_warn" seems to indicate that it's meant to remain unused, even if it probably should be checked.
Would you rather the warning be turned off on some level?
-bw
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