Messages in this thread | | | Date | Tue, 1 Nov 2022 06:46:56 +0100 | From | Jiri Slaby <> | Subject | Re: [PATCH] block/blk-iocost (gcc13): cast enum members to int in prints |
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On 31. 10. 22, 18:57, Tejun Heo wrote: > On Mon, Oct 31, 2022 at 05:24:28AM -0700, Christoph Hellwig wrote: >> On Mon, Oct 31, 2022 at 12:45:20PM +0100, Jiri Slaby (SUSE) wrote: >>> Cast the enum members to int when printing them. >>> >>> Alternatively, we can cast them to ulong (to silence gcc < 12) and use %lu. >>> Alternatively, we can move VTIME_PER_SEC away from the enum. >> >> Yes, either split the enum or just use a define. But casts are a big >> code smell and should be avoided if there is a reasonable alternative. > > enums are so much better for debugging and other instrumentation stuff. The > only requirement for the enum types is that they're big enough to express > all the members and we can use whatever printf format letter which matches > the type in use. The problem here is that the compiler behavior is different > depending on the compiler version, which kinda sucks.
Yes. The real problem is that using anything else then an INT_MIN <= x <= INT_MAX _constant_ in an enum is undefined in ANSI C < 2x (in particular, 1 << x is undefined too). gcc manual defines unsigned int on the top of that as defined too (so this holds for our -std=g*).
> I suppose the most reasonable thing to do here is just splitting them into > separate enum definitions. Does anyone know how this behavior change came to > be?
C2x which introduces un/signed long enums. See the bug I linked in the commit log: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36113
The change is also turned on in < C2x on purpose. AIUI, unless there is too much breakage. So we'd need to sort it out in (rather distant) future anyway (when we come up to -std=g2x).
> Do we know whether clang is gonna be changed the same way?
In C2x, Likely. In < C2x, dunno what'd be the default.
thanks, -- js suse labs
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