Messages in this thread | | | Date | Sat, 6 Dec 2008 09:16:19 +0100 | From | Willy Tarreau <> | Subject | Re: [RFC] Recursive printk |
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On Fri, Dec 05, 2008 at 11:41:05PM -0800, Andrew Morton wrote: > On Sat, 6 Dec 2008 08:33:05 +0100 Willy Tarreau <w@1wt.eu> wrote: > > > On Fri, Dec 05, 2008 at 11:20:16PM -0800, Andrew Morton wrote: > > > > void snd_verbose_printk(const char *file, int line, const char *format, ...) > > > > { > > > > va_list args; > > > > > > > > if (format[0] == '<' && format[1] >= '0' && format[1] <= '7' && format[2] == '>') { > > > > char tmp[] = "<0>"; > > > > tmp[1] = format[1]; > > > > printk("%sALSA %s:%d: ", tmp, file, line); > > > > format += 3; > > > > > > That's racy. Two threads can fight over tmp[1]. It should do: > > > > > > printk("<%c>ALSA %s:%d: ", format[1], tmp, file, line); > > > > > > (I didn't know that you can even modify literal strings - shouldn't > > > they be in read-only storage?) > > > > no Andrew, this tmp[] is declared on the stack, and gcc emits code to > > copy the constant "<0>" onto the stack every time this code is called > > Good heavens, so it does. It is unusual for C to cater to such stupid > code by generating such inefficient code. A bit of a trap, really.
especially since teachers tend to explain students that char foo[] is the same thing as char *foo, which obviously it is not.
Willy
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