Re: [PATCH] Fix wrong code with truncated string literals (PR 86711/86714)

[Jeff Law <law at redhat dot com>]

On 08/03/2018 03:28 PM, Jakub Jelinek wrote:
> On Fri, Aug 03, 2018 at 03:16:41PM -0600, Jeff Law wrote:
>> On 07/31/2018 12:33 AM, Jakub Jelinek wrote:
>>> On Mon, Jul 30, 2018 at 10:01:38PM -0600, Martin Sebor wrote:
>>>>> We do not want to change what is currently accepted by the
>>>>> front end. period.
>>>>
>>>> On whose behalf are you making such categorical statements?
>>>> It was Jakub and Richard's suggestion in bug 86714 to reject
>>>> the undefined excessive initializers and I happen to like
>>>> the idea.  I don't recall anyone making a decision about what
>>>
>>> It was not my suggestion and it is already rejected with -pedantic-errors,
>>> which is all that is needed, reject it in pedantic mode.
>>> Otherwise there is a warning emitted by default which is enough.
>> But I think that's a mistake.  I think a hard error at this point is
>> warranted and the safest thing to do.
> 
> The normal behavior when it isn't an error is that the initializer is
> truncated.  That is what happens if I use
> struct S { char a[4]; };
> struct S r = { "abc" };
> struct S s = { "abcd" };
> struct S t = { "abcde" };
> 
> C says that in the s.a initializer is actually just 'a', 'b',
> 'c', 'd' rather than 'a', 'b', 'c', 'd', '\0', so there is a silent
> truncation in the language naturally, so the extension that truncates even
> more with a warning enabled by default is IMHO natural and doesn't need to
> be more pedantic.  We've always truncated, so there should be no surprises.
I wasn't aware C mandated a behavior here.  With that in mind I think we
truncate per the C semantics and get on with our lives :-)

Jeff