[RFC] Question on gfortran extension

[Jerry DeLisle]

Mike Kumbera wrote:
> I think this extension was added by Asher for llnl. The examples
> that failed all had the form:
> 
> integer :: a
> data a /5/
> data a /5/
> print '(3i6)', a
> end
> 
> In these cases we didn't care if the first or last data statment was used.
> 
> gfortran was the first fortran compiler to catch this bug. The compiler 
> generated an ICE on this. I don't care if a warning is issued as the 
> default action. It also doesn't matter if the first or last data statement 
> is used since the code is not officially allowed. 
> 
> Since the all the commercial compilers (intel, pgi, pathscale and xlf)
> take the code, I think we should keep the extension but issue a stern 
> warning. :-) The first step to removing this nonstandard code from all 
> our applications is for us to know it's in there. 
> 
> Mike
> 
> 
> On Fri, Nov 17, 2006 at 10:21:16PM -0800, Jerry DeLisle wrote:
>> Hi all,
>>
>> In working on PR24978 I am looking at several test cases.  Currently the 
>> following test case is accepted by gfortran as an extension:
>>
>> integer :: a
>> data a /5/
>> data a /8/
>> print '(3i6)', a
>> end
>>
>> The result is that the variable 'a' is assigned the value 5 because that 
>> data statement is the last to be resolved even though intuitively one might 
>> think the last data statement ought to take effect. (Resolution occurs in 
>> reverse statement order)
>>
>> This extension really goes against the F95 Standard which does not allow 
>> duplicate initialization.  It is my opinion that this is a dangerous 
>> extension. As implemented now, it only warns if one specifies -pedantic 
>>  and errors if given -std=f95 or -std=f2003.  This can leave users open to 
>> inadvertent duplicate initialization if they do not use the options.
>>
>> I am wondering if we should keep this extension at all and if so should we 
>> at least warn as default and error on -pedantic and/or -std=fxx?
>>
>> Also, if we do keep this extension, should we keep the assignment given in 
>> the last data statement rather than the first?
>>
>> Regards,
>>
>> Jerry
> 
Thanks for this information.  I think what I will do is add a flag 
-fallow-duplicates or similar, otherwise error.

Jerry