Messages in this thread | | | From | Andy Lutomirski <> | Date | Fri, 18 Jul 2014 13:08:51 -0700 | Subject | Re: linux-next: build warning after merge of the tip tree |
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On Fri, Jul 18, 2014 at 1:05 PM, H. Peter Anvin <hpa@zytor.com> wrote: > On 07/18/2014 12:57 PM, Andy Lutomirski wrote: >> >> This particular warning is IMO in a particularly dumb category: GCC >> optimizes some code and then warns about a construct that wasn't there >> in the original code. In this case, I think it unrolled a loop and >> discovered that one iteration contained a test that was always true. >> Big deal. >> >> (OTOH, the code in question was buggy, but not all for the reason that >> GCC thought it was.) >> > > if (syms[sym_vvar_start] > syms[i] + 4096) > fail("%s underruns begin_vvar\n", > required_syms[i].name); > > if i == sym_vvar_start then this is at least a valid warning. It could > easily be quieted by chaning syms[] to an unsigned array.
Hah -- fooled you, too :)
i isn't an index in to the syms array at all. This code is completely wrong. See the patch I sent in reply to Stephen's original email.
But, to your earlier point, presumably this could warn:
for (int i = 0; i < 10; i++) if (array[i] > array[5] + 1) fail();
I think that's absurd. There's nothing wrong with that code. A given test should have to be always true or always false on *all* loop iterations to be flagged, I think.
--Andy
> > -hpa >
-- Andy Lutomirski AMA Capital Management, LLC
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