On 10/05/2016 09:40 AM, Joseph Myers wrote:
On Tue, 4 Oct 2016, Martin Sebor wrote:
Well, typically cases where one of long and int is passed and the other is
expected, but they have the same size, are bugs waiting to happen when the
code is built on a 64-bit system. That is, they *should* warn.
Typically, yes. In the case of wchar_t (or int) and wint_t I don't
think it's helpful. Consider this case from my comment #5 on bug
72858. I don't think there is any point in issuing a warning here.
On the majority of targets they either all are or promote to a type
of the same size, don't they?
I'm unconvinced by that "majority of targets" of argument (which once
would have been true for int and long, and you could say it is true for
long and size_t). There's a clear correct type here, and it's wint_t, and
it's always easy to fix the code to use the correct type.
The warning would only helpful if there was a target where wchar_t
didn't promote to a type with the same precision as wint_t, or in
other words where printf("%lc", L'a') did something different than
printf("%lc", (wint_t) L'a'). I don't know of such a target. Can
you give an example of one?
It isn't any of the ILP32 targets where wint_t is int and wchar_t
is long and where the warning was found to cause test suite failures,
and it isn't any other other targets where the warning didn't trigger
because the two types have the same precision.
Otherwise, when there is no such target there is nothing to fix, and
changing working code just for the sake of pedantry only runs the
unnecessary risk of introducing bugs. IMO, this is especially true
in subtle cases like this where the people who make the changes often
don't fully appreciate the subtleties of the code. Suggesting the
wrong directive (replacing %lc with %ld) compounds the problem
further(*).
Martin
[*] This is not meant as a dig at David but rather to underscore
that both the "problem" is subtle and the expected solution not
obvious.
