Re: not computable at load time

[Jeff Law <law@redhat.com>]

On 05/29/2018 03:49 AM, Richard Biener wrote:
> On Mon, May 28, 2018 at 8:34 PM Paul Koning <paulkoning@comcast.net> wrote:
> 
> 
> 
>>> On May 28, 2018, at 12:03 PM, Richard Biener
>> <richard.guenther@gmail.com>
> wrote:
>>>
>>> On May 28, 2018 12:45:04 PM GMT+02:00, Andreas Schwab <schwab@suse.de>
> wrote:
>>>> On Mai 28 2018, Richard Biener <richard.guenther@gmail.com> wrote:
>>>>
>>>>> It means there's no relocation that can express the result of 's.f -
>>>> &s.b'
>>>>> and the frontend doesn't consider this a constant expression (likely
>>>> because
>>>>> of the conversion).
>>>>
>>>> Shouldn't the frontend notice that s.f - &s.b by itself is a constant?
>>>
>>> Sure - the question is whether it is required to and why it doesn't.
> 
>> This is a test case in the C torture test suite.  The only  reason
>> I can see for it being there is to verify that GCC resolves this as
>> a compile time constant.
> 
>> The issue can be masked by changing the "long" in that test case to
>> a ptrdiff_t, which eliminates the conversion.  Should I do that?
>> It would make the test pass, at the expense of masking this glitch.
> 
>> By the way, I get the same error if I change the "long" to a "long long"
>> and them compile for 32-bit Intel.
> 
> The testcase dates back to some repository creation rev. (egcs?) and
> I'm not sure we may compute the difference of addresses of structure
> members.  So that GCC accepts this is probably not required.  Joseph
> may have a definitive answer here.
Given the name 93xxxx.c it goes back to the c-torture releases from
Torbjorn which were separate from GCC releases.  His c-torture suite
helped seed the integrated regression testsuite.;

Jeff