Messages in this thread | | | From | "Alexander van Heukelum" <> | Subject | Re: [PATCH 4/5 v2] x86 boot: show pfn addresses in hex not decimal in some kernel info printks | Date | Mon, 30 Jun 2008 09:58:28 +0200 |
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On Wed, 25 Jun 2008 08:19:13 -0700 (PDT), "Linus Torvalds" <torvalds@linux-foundation.org> said: > On Wed, 25 Jun 2008, Johannes Berg wrote: > > > > In networking, we've gone through various incarnations of print_mac() > > which is similar to the sym() macro Paul proposed, and it turned out to > > be undesirable because of the way it interacts with static inlines that > > only optionally contain code at all, the print_mac() function call is > > still emitted by the compiler. People experimented with marking it > > __pure but that had other problems. > > You don't even have to go that esoteric. > > Just printing things like "sector_t" or "u64" is painful, because the > exact type depends on config options and/or architecture. > > > It would be nice to be able to say > > > > u8 *eaddr; > > > > printk(... %M ..., eaddr); > > For special things, I do think we should extend the format more, and > forget about single-character names. It would be lovely to do them as > %[mac], %[u64], %[symbol] or similar. Because once you don't rely on gcc > checking the string, you can do it.
That would confuse the gcc format string checking... A solution that just crossed my mind is leaving the format string as is (i.e., "%p"), but prepending it with a special linux-specific string which does not confuse gcc. Like: "&mac%p"... for simplicity & can be considered always special in printk, and && can stand for a literal &. (or pick any other character that is not used frequently in format strings and is not %, of course.)
> The problem is that right now we absolutely _do_ rely on gcc checking the > string, and as such we're forced to use standard patterns, and standard > patterns _only_. And that means that %M isn't an option, but also that if > we want symbolic names we'd have to use %p, and not some extension.
"&%p" could then be used for a symbol-lookup.
It doesn't help u64, though, but isn't it about time to unify u64 to "unsigned long long" everywhere, anyhow? Is there any argument against that except that a big sweep is necessary to clean up new warnings due to printk format strings?
Greetings, Alexander
> But once you drop the 'standard patterns' requirement, I do think you > should drop it _entirely_, and not just extend it with some pissant > single-character unreadable mess. > > Linus > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" > in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > > -- Alexander van Heukelum heukelum@fastmail.fm
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