Messages in this thread | | | Date | Tue, 27 Jul 2021 15:13:28 -0500 | From | Segher Boessenkool <> | Subject | Re: [PATCH v2 1/3] base: mark 'no_warn' as unused |
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On Tue, Jul 27, 2021 at 07:59:24PM +0200, Greg Kroah-Hartman wrote: > On Tue, Jul 27, 2021 at 10:39:49AM -0700, Nick Desaulniers wrote: > > I think warn_unused_result should only really be used for functions > > where the return value should be used 100% of the time. > > I too want a shiny new pony. > > But here in the real world, sometimes you have functions that for 99% of > the users, you do want them to check the return value, but when you use > them in core code or startup code, you "know" you are safe to ignore the > return value. > > That is the case here. We have other fun examples of where people have > tried to add error handling to code that runs at boot that have actually > introduced security errors and they justify it with "but you have to > check error values!" > > > If there are > > cases where it's ok to not check the return value, consider not using > > warn_unused_result on function declarations. > > Ok, so what do you do when you have a function like this where 99.9% of > the users need to check this? Do I really need to write a wrapper > function just for it so that I can use it "safely" in the core code > instead? > > Something like: > > void do_safe_thing_and_ignore_the_world(...) > { > __unused int error; > > error = do_thing(...); > } > > Or something else to get the compiler to be quiet about error being set > and never used?
The simplest is to write if (do_thing()) { /* Nothing here, we can safely ignore the return value * here, because of X and Y and I don't know, I have no * idea actually why we can in this example. Hopefully * in real code people do have a good reason :-) */ }
which should work in *any* compiler, doesn't need any extension, is quite elegant, and encourages documenting why we ignore the return value here.
Segher
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