Re: gcc 4.3.0, -Wconversion: assignment-by operators for shorter types

["Manuel López-Ibáñez" <lopezibanez at gmail dot com>]

2008/5/28 Andriy Gapon <avg@icyb.net.ua>:
> on 27/05/2008 22:00 Andrew Pinski said the following:
>>
>> On Tue, May 27, 2008 at 11:56 AM, Andriy Gapon <avg@icyb.net.ua> wrote:
>>>
>>> Thank you for the explanation! I didn't realize the difference.
>>>
>>> OTOH, do you think that those arithmetic warnings are practical (as
>>> opposed
>>> to being correct)?
>>
>> I think so as the short int case has a defined overflow of the signed
>> short type that is SHRT_MAX + 1 is defined while INT_MAX + 1 is not.
>
> I still feel like disagreeing.
> Consider this:
> *************
> int main()
> {
>        short short_x;
>
>        short_x = short_x + 1;
>        short_x += 1;
>        short_x++;
>        ++short_x;
>
>        return 0;
> }
> *************
>
> $ gcc43 -Wconversion test-conv2.c -o test-conv
> test-conv2.cc: In function 'int main()':
> test-conv2.cc:5: warning: conversion to 'short int' from 'int' may alter its
> value
> test-conv2.cc:6: warning: conversion to 'short int' from 'int' may alter its
> value
>
> I thought that in C all 4 forms were equivalent and this was purely a style
> choice. Now they are different.
>

Please open a bug report (http://gcc.gnu.org/bugs.html) with this
issue and add manu@gcc.gnu.org to the CC list. Otherwise this will be
forgotten.

Cheers,

Manuel.