Re: [PATCH v2] malloc_stats(): Fix `unsigned int` overflow

[DJ Delorie <dj@redhat.com>]

Niklas Hambchen <mail@nh2.me> writes:
>>> +  fprintf (stderr, "max mmap regions = %10d\n", mp_.max_n_mmaps);
>> 
>> This causes a negative number to be printed when max_n_mmaps increments
>> past 2^31, where using "u" defers bad results until 2^32.  So IMHO this
>> one is a regression, not a fix.
>
> I'm not sure I understand:
> That statement holds for all `int`s, so following this logic, all
> `int`s should be casted to `unsigned int` first and printed with `%u`,
> and `%d` would be quite useless.
>
> Doesn't it make more sense to print an `int` with `%d` as normal, so
> that you can _see_ in `malloc_stats()` when it overflows?

It only really overflows when it wraps around 2^32.  Until then, the
value is still useful, as long as you present it properly.

An alternative would be to print out "(overflowed)" if the value exceeds 2^31

It just didn't seem right to take something that prints 0..2^32-1 and
reduce it to only print 0..2^31-1.

The other cases were stored as size_t and potentially truncated, which
is a different sort of overflow bug.