[patch, fortran] PR38291 Rejects I/O with POS= if FMT=*

[jvdelisle@verizon.net]

Here is a revised patch.  I found a problem with positioning on a read 
in that I was not checking end-of-file and setting 
dtp->u.p.current_unit->endfile = NO_ENDFILE. This has to be done for the 
case of an empty read in data_transfer_init.  Otherwise, we get an EOF 
error for every read in list_read.c (finish_list_read ).

This brings up a subtle point.  With list directed input and an empty 
input list, the F2003 standard says that the current record is skipped. 
If I create a small file with no end-of-record marker (LF) and attempt a 
list directed read with no input list (empty read), gfortran dutifully 
trys to read through, looking for the end-of-record marker and hits the 
end-of-file, giving an error. At least one other compiler I have does 
not give an error and seems to interpret the EOF as the EOR in the case 
of "skipping the record.

Regardless the final patch is regression tested.

Since the change I made since Tobias approval is very minor, I will 
commit. (See small portion of change below.

Regards,

Jerry

+         if (dtp->u.p.mode == READING)
+           {
+             /* Required for compatibility between 4.3 and 4.4 runtime. 
Check
+             to see if we might be reading what we wrote before  */
+             if (dtp->u.p.current_unit->mode == WRITING)
+               flush(dtp->u.p.current_unit->s);
+
+             if (dtp->pos < file_length (dtp->u.p.current_unit->s)) 
<---This added
+               dtp->u.p.current_unit->endfile = NO_ENDFILE;
+           }




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