Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 26 Nov 2019 15:04:06 +0100 | Subject | Re: [PATCH v4 0/1] printf: add support for printing symbolic error names |
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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 ;-)
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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