[patch, fortran]PR25829 Add support for F2003 I/O features

[Tobias Burnus]

Jerry DeLisle wrote:
> The attached updated patch incorporates all constraints and checks
> listed above in the front end.  It also implements the DP and DC format
> specifiers.
>   
Thanks. Some more issues and remarks. I will try to review the patch later.


* There should be a "Fortran 2003:" in the error message.
+         if (gfc_notify_std (GFC_STD_F2003, "DP format specifier not 
allowed "


* decimal= in INQUIRE does not seem to be supported:
  inquire(unit=99, decimal=d)
Same for:
  inquire(99,encoding=str)
I also think the error messages can be improved:
  inquire(99, BLANK='foo')
            1
  Error: Syntax error in INQUIRE statement at (1)
NAG has a better error message: "Item for i/o keyword BLANK is not a 
variable"


* write(99,decimal=foo) 4.4, 3.3
This gives a run-time error message, but it can be detected at compile 
time. NAG f95 has:
   Error: DECIMAL= is incompatible with unformatted i/o
Actually, the run-time error message is also a bit misleading:
   Fortran runtime error: Missing format for FORMATTED data transfer


* Analogously for the following:
  write(99,DELIM=str)
which is also not allowed  for unformatted I/O


* "Error: F2003 Feature: SIGN=specifier at (1) not implemented"
Can you add a space after the "=" sign?

* write(99,id=id)
This is invalid as asynchronous="yes" needs to be specified as well. 
However, this is not enforced in the front end (or library).

* The following program crashes in _gfortran_st_wait (transfer.c:2966) 
("Invalid write of size 4"):
  integer :: id
  open(99, asynchronous='yes')
  write(99,asynchronous='yes',id=id,fmt=*)
  wait(99,id=id)
  end

* The following program is invalid, but only detectable at run time. 
Should there be a run-time check? Maybe one should postpone this until 
the real asynchronous is available:
  integer :: id
  open(99, asynchronous='no')
  write(99,asynchronous='yes',id=id,fmt=*)
  end
But I think we need such a check for the real implementation.

I played a bit around with the decimal comma support and it nicely works :-)

Tobias