Messages in this thread | | | Date | Wed, 27 Nov 2019 09:54:51 +0100 | From | Petr Mladek <> | Subject | Re: [PATCH v4 0/1] printf: add support for printing symbolic error names |
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On Tue 2019-11-26 15:04:06, Geert Uytterhoeven wrote: > Hi Rasmus, > > Nice idea! > > On Fri, Oct 11, 2019 at 3:38 PM Rasmus Villemoes > <linux@rasmusvillemoes.dk> wrote: > > This is a bit much for under the ---, so a separate cover letter for > > this single patch. > > > > v4: Dropped Uwe's ack since it's changed quite a bit. Change > > errcode->errname as suggested by Petr. Make it 'default y if PRINTK' > > so it's available in the common case, while those who have gone to > > great lengths to shave their kernel to the bare minimum are not > > affected. > > > > Also require the caller to use %pe instead of printing all ERR_PTRs > > symbolically. I can see some value in having the call site explicitly > > indicate that they're printing an ERR_PTR (i.e., having the %pe), but > > I also still believe it would make sense to print ordinary %p, > > ERR_PTR() symbolically instead of as a random hash value that's not > > stable across reboots. But in the interest of getting this in, I'll > > leave that for now. It's easy enough to do later by just changing the > > "case 'e'" to do a break (with an updated comment), then do an > > IS_ERR() check after the switch. > > > > Something I've glossed over in previous versions, and nobody has > > commented on, is that I produced "ENOSPC" while the 'fallback' would > > print "-28" (i.e., there's no minus in the symbolic case). I don't > > care much either way, but here I've tried to show how I'd do it if we > > want the minus also in the symbolic case. At first, I tried just using > > the standard idiom > > > > if (buf < end) > > *buf = '-'; > > buf++; > > > > followed by string(sym, ...). However, that doesn't work very well if > > one wants to honour field width - for that to work, the whole string > > including - must come from the errname() lookup and be handled by > > string(). The simplest seemed to be to just unconditionally prefix all > > strings with "-" when building the tables, and then change errname() > > back to supporting both positive and negative error numbers. > > Still, it looks a bit wasteful to me to include the dash in each and every > string value. > > Do you think you can code the +/- logic in string_nocheck() in less than > the gain achieved by dropping the dashes from the tables? > (e.g. by using the SIGN spec.flags? ;-) > Or, do we need it? IS_ERR() doesn't consider positive values errors. > > Oh, what about the leading "E"? That one looks harder to get rid of, > though ;-)
It would be nice. But too big hack is not worth it. Anybody who cares about saving 0.2kB would likely disable this feature completely.
Feel to provide a patch so that we could see how good/bad it is.
Best Regards, Petr
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