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Re: PATCH RFC: -Wstrict-overflow, take 2
On February 16 2007, "Ian Lance Taylor" wrote to "Jonathan Lennox, gcc-patches@gcc.gnu.org" saying:
> Jonathan Lennox <lennox@cs.columbia.edu> writes:
> > How hard would it be to change this diagnostic to print the actual values of
> > "X", "+-", "C1", "cmp", and "C2"?
> >
> > For expmed.c:3485, for example, the warning would be
> >
> > ../../trunk/gcc/expmed.c:3485: warning: assuming signed overflow does not
> > occur when changing "size - 1 < 32" to "size < 32 + 1"
> >
> > I think this would be much more accessible to people not versed in the
> > intricacies of compilers, and also make it much easier (as in this case) to
> > see at a glance if signed overflow could actually be a problem.
>
> Well, the X can, in general, be anything. As far as I know we don't
> have a good way to dump general expressions in warning contexts. But
> maybe I just don't know about it.
>
> The C1 and C2 are integer constants, and would be easy to dump. It's
> line 8296 of fold-const.c. Go for it.
The tricky points are that a) fold_overflow_warning doesn't take a
formatting string, and b) I don't have a GCC copyright assignment, and my
current work situation would make it non-trivial to acquire one.
I could file an enhancement request PR, I suppose.
--
Jonathan Lennox
lennox at cs dot columbia dot edu