http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50926
Tobias Burnus <burnus at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |burnus at gcc dot gnu.org
--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-10-31
08:09:01 UTC ---
(In reply to comment #0)
> Console output suddenly stops to be console: at some point (usually when
> write(*,*) and write(6,*) operators are being used for some times
Only glancing at your summary, I would assume the following: Your program does
at some point:
close(6)
In gfortran (and most other compilers), the unit * and the unit 6 are the same
unit. Thus, if you 'open(6, file="test.dat")', all output of write(*,*) and of
write(6,*) go into the same file.
Thus, if you expect that 6 and * are separately, you might easily get in
trouble. The Fortran 2003 standard explicitly states that the OUTPUT_UNIT and
unit * end up in the same file. (The OUTPUT_UNIT parameter is part of the
intrinsic ISO_Fortran_env module and has in gfortran the value 6.)
The only compiler I know, which treats the units * and 6 differently, is the
Intel compiler. In order to get the proper Fortran 2003 behaviour, one needs to
specify -assume noold_unit_star.
Note additionally that after close(6), it is really depends on the compiler
whether how it behaves:
* it might use again the console as output (ifort, pathf95)
* create a file "fort.6" or similar (gfortran, g95)
* or give an error because the unit has been close (NAG f95)
Thus: Please avoid to call OPEN to connect the units 0 to 9 to a file - unless
you want to direct all output to a file - and even then, avoid to call CLOSE
for those units.
I mention 0 to 9 as those are the most likely units for console-related I/O. In
gfortran and most other compilers, the units are 0 (ERROR_UNIT), 5 (INPUT_UNIT)
and 6 (OUTPUT_UNIT).
