Messages in this thread | | | Date | Tue, 7 Mar 2017 10:01:44 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86/fpu: fix boolreturn.cocci warnings |
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(Linus and Andrew Cc:-ed)
* Thomas Gleixner <tglx@linutronix.de> wrote:
> On Tue, 7 Mar 2017, Ingo Molnar wrote: > > > > * kbuild test robot <fengguang.wu@intel.com> wrote: > > > > > arch/x86/kernel/fpu/xstate.c:931:9-10: WARNING: return of 0/1 in function 'xfeatures_mxcsr_quirk' with return type bool > > > > > > Return statements in functions returning bool should use > > > true/false instead of 1/0. > > > > Note that this is a totally bogus warning. I personally find a 0/1 return more > > readable than a textual 'true/false', even if bools are used, and nowhere does the > > kernel mandate the use of 0/1. > > I disagree. > > The fact that booleans have been brought retroactively into the C-Standard > does and for compability reasons C still follows the approach "Boolean > values are just integers" does not make it any better. > > We had stupid bugs, where people returned -EINVAL from a boolean function > and introduced silly and hard to understand bugs.
But this function is not using -EINVAL, it's using 0 and 1 which is both correct and unambiguous!
I mean, if the Cocci script warned about -EINVAL then it would have found a clear bug. Now it's warning about the use of 0/1 literals with bool types which is perfectly legal, readable, clear C code!
> The canonical values assigned to booleans are 'true' and 'false' and not > whatever people prefer. Can we please be consistent on that?
I think that's backwards, because 1/0 is just as canonical for true/false, and to me personally it's in fact easier to read as well.
I would really like higher level buy-in for that principle (I've Cc:-ed Linus and Andrew), and if indeed the consensus is that '0/1' cannot be used with 'bool' then I'll remove all uses of 'bool' from my patches and from code I care about and use 'int' instead. Please update Documentation/CodingStyle accordingly as well.
To me a lexical 'true/false' instead of '1/0' is a step backwards in readability in many cases - using the slightly wider 'int' type is the lesser evil.
Thanks,
Ingo
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