Linus Torvalds <torvalds@transmeta.com> writes:
|> On Tue, 25 Feb 2003, Andreas Schwab wrote:
|> > |>
|> > |> So? Gcc does that anyway. _Any_ good compiler has to.
|> >
|> > But the point is that determining the common type does not require _any_
|> > kind of data flow analysis, and this is the place where the unsigned
|> > warning is generated.
|>
|> Go back and read my mail. In fact, go back and read just about _any_ of my
|> mails on the subject. Gop back and read the part you snipped:
|>
|> "And if the compiler isn't good enough to do it, then the compiler
|> shouldn't be warning about something that it hasn't got a clue about."
|>
|> In other words, either gcc should do it right, or it should not be done at
|> all. Right now the warning IS GENERATED IN THE WRONG PLACE. Your argument
|> seems to be "but that's the place it is generated" is a total
|> non-argument. It's just stating a fact, and it's exactly that fact that
|> causes the BUG IN GCC.
Then we have to agree to disagree. Signed/unsigned mixups are just too
easy to get wrong in C, and a constant source of security bugs.
|> > |> Trivial example:
|> > |>
|> > |> int x[2][2];
|> > |>
|> > |> int main(int argc, char **argv)
|> > |> {
|> > |> return x[1][-1];
|> > |> }
|> > |>
|> > |>
|> > |> the above is actually a well-defined C program, and 100%
|> > |> standards-conforming ("strictly conforming").
|> >
|> > This isn't as trivial as it seems. Look in comp.std.c for recent
|> > discussions on this topic (out-of-array references).
|>
|> It is as trivial as it seems, and this is _not_ an out-of-array reference.
It is out of the x[1] array, *if* you consider it an object of its own
(whether this is the right viewpoint is the point of the issue).
|> So if they argued about this on comp.std.c, they either had clueless
|> people there (in addition to the ones that obviously aren't ;), _or_ you
|> misunderstood the argument.
I'd guess that the language experts on comp.std.c are more clueful about
the C standard than both you and me.
Andreas.
-- Andreas Schwab, SuSE Labs, schwab@suse.de SuSE Linux AG, Deutschherrnstr. 15-19, D-90429 Nürnberg Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different." - 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/
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