Re: Feature request: gcc should warn upon conversions ptrdiff_t -> int
On Thu, Jun 12, 2003 at 07:06:42AM +0200, Martin v. L?wis wrote:
> Phil Edwards <phil@jaj.com> writes:
>
> > > int foo(int *x, int *y)
> > > {
> > > return x - y;
> > > }
> >
> > There is no conversion to int. foo* may be subtracted from foo* for any
> > type foo. It's normal pointer arithmetic. This code is fine.
>
> You are missing the point. The result of the subtraction is of type
> ptrdiff_t (which is fine), but then, on the return, that gets
> converted to int.
Oh, /return/ type. Yes, I missed that; thanks for pointing it out.
I won't have access to a non-ILP32 system for a couple of weeks, but I'd
be willing to bet that on systems where ptrdiff_t is larger than int,
this code already elicts a warning, probably via -Wconversion.
For platforms where they are the same... eugh. You'd like a warning on
constructs that "might" cause portability problems, but given that it's
just a typdef, all the semantic analysis routines will simply see two
identical types. Implementing this would be hard. Hmmm.
Phil
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