read CSV data consistently from string or file

[Jerry DeLisle]

On 10/13/18 9:23 AM, Jerry DeLisle wrote:
> On 10/12/18 4:52 PM, Jerry DeLisle wrote:
>> On 10/12/18 1:10 PM, Browning, Robert S IV ERDC-RDE-GSL-MS CIV wrote:
>>> I am needing to read in a text file that contains numerical data 
>>> separated by keywords. Because of the keywords, I need to read each 
>>> line in as text first and test if it’s a keyword, and then call the 
>>> appropriate subroutine based on the keyword value. Within the 
>>> subroutines I also need to read each line as text first so I can stop 
>>> the subroutine when the next keyword is found.
>>> The numerical data can be in either fixed format or 
>>> comma-separated-value (CSV) format. In the CSV data, a zero could be 
>>> represented by a pair of commas with no number between them.
>>> The issue I have encountered is that the read statement appears to 
>>> behave differently when it is reading from a character string than 
>>> when it is reading directly from the input file. If I were able to 
>>> read directly from the input file, then a simple formatted read 
>>> statement does everything I need. But if I am reading from a string, 
>>> then things get a bit more complicated.
>>
>> Hi Robert,
>>
>> This may be a known bug. It sounds familiar. Let me do some checking.
>>
>> Fortranners, if I confirm this is the bug I think it is, I think I can 
>> squeeze some time to fix it.
>>
>> Jerry
>>
> 
> I am fairly certain this is PR78351. As far as we can tell the code is 
> non-conforming Fortran but the use of comma to terminate a read has been 
> around forever and gfortran supported this before.  It was my breakage 
> in my endeavors to improve string I/O performance. I feel obligated at 
> this point to set it straight.
> 
> Jerry
> 

The patch attached to pr78351 fixes this and regression tests cleanly.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78351

I am wondering if I should put the check behind some condition related 
to the standards to avoid the extra string scan or just leave it as is 
in the patch.

Regards,

Jerry