On 2/21/2024 6:55 PM, Arne Vajhøj wrote:
But let us take a step back and look at a slightly more
reasonable example.
$ type soso.for
program soso
integer*4 a(2)
common /m/a
call s
write(*,*) a(1),a(2)
end
c
subroutine s
integer*4 a(2)
common /m/a
data a/123,456/
end
$ for soso
$ link soso
$ r soso
123 456
Which may not be good code as it is rather unclear
where the data initialization happens, but not nearly
as bad as the code further above.
And I believe that style is widely used on VMS. BLOCK DATA
are not often used on VMS. I mostly see them used for writeable
shareable images - and that is a very special case.
$ type bad.for
program bad
integer*4 a(2)
common /m/a
call s1
call s2
write(*,*) a(1),a(2)
end
c
subroutine s1
integer*4 a(2)
common /m/a
data a(1)/123/
end
c
subroutine s2
integer*4 a(2)
common /m/a
data a(2)/456/
end
$ for bad
$ link bad
$ r bad
123 456
Is really ugly code. But it worked on VMS VAX 40 years ago,
so the expectation is that it works on VMS x86-64 today.
Backwards compatibility can be a real PITA.
It is possible to ask for stronger standard compliance check.
$ for/stand=f95 soso
program soso
^
%F90-W-WARNING, Fixed form source is an obsolescent feature in Fortran 95.
at line number 1 in file DKA0:[arne]soso.for;1
integer*4 a(2)
..............^
%F90-W-WARNING, Fortran 95 does not allow this length specification. [4] at line number 2 in file DKA0:[arne]soso.for;1
integer*4 a(2)
..............^
%F90-W-WARNING, Fortran 95 does not allow this length specification. [4] at line number 9 in file DKA0:[arne]soso.for;1
data a/123,456/
...........^
%F90-W-WARNING, In Fortran 95, this DATA statement object cannot appear
in either a blank COMMON block or a named COMMON block. [A]
at line number 11 in file DKA0:[arne]soso.for;1
$ for/stand=f95 bad
program bad
^
%F90-W-WARNING, Fixed form source is an obsolescent feature in Fortran 95.
at line number 1 in file DKA0:[arne]bad.for;1
integer*4 a(2)
..............^
%F90-W-WARNING, Fortran 95 does not allow this length specification. [4] at line number 2 in file DKA0:[arne]bad.for;1
integer*4 a(2)
..............^
%F90-W-WARNING, Fortran 95 does not allow this length specification. [4] at line number 10 in file DKA0:[arne]bad.for;1
data a(1)/123/
...........^
%F90-W-WARNING, In Fortran 95, this DATA statement object cannot appear
in either a blank COMMON block or a named COMMON block. [A]
at line number 12 in file DKA0:[arne]bad.for;1
integer*4 a(2)
..............^
%F90-W-WARNING, Fortran 95 does not allow this length specification. [4] at line number 16 in file DKA0:[arne]bad.for;1
data a(2)/456/
...........^
%F90-W-WARNING, In Fortran 95, this DATA statement object cannot appear
in either a blank COMMON block or a named COMMON block. [A]
at line number 18 in file DKA0:[arne]bad.for;1
Both the INTEGER*4 declaration and the mix of COMMON and DATA
are not valid per Fortran 95 standard resulting in the warning.
But with old VMS Fortran code that qualifier is pretty rare.
Note that VMS Fortran is not unique in accepting that code.
I have not been able to find a Fortran compiler not accepting
it by default.
GFortran:
C:\Work\Fortran>gfortran soso.for -o soso.exe
C:\Work\Fortran>soso
123 456
C:\Work\Fortran>gfortran bad.for -o bad.exe
C:\Work\Fortran>bad
123 0
C:\Work\Fortran>gfortran -std=f95 soso.for -o soso.exe
soso.for:2:16:
2 | integer*4 a(2)
| 1
Error: GNU Extension: Nonstandard type declaration INTEGER*4 at (1) soso.for:5:18:
5 | write(*,*) a(1),a(2)
| 1
Error: PROCEDURE attribute conflicts with COMMON attribute in 'a' at (1) soso.for:9:16:
9 | integer*4 a(2)
| 1
Error: GNU Extension: Nonstandard type declaration INTEGER*4 at (1) soso.for:11:13:
11 | data a/123,456/
| 1
Error: GNU Extension: initialization of common block variable 'a' in
DATA statement at (1)
C:\Work\Fortran>gfortran -std=f95 bad.for -o bad.exe
bad.for:2:16:
2 | integer*4 a(2)
| 1
Error: GNU Extension: Nonstandard type declaration INTEGER*4 at (1) bad.for:6:18:
6 | write(*,*) a(1),a(2)
| 1
Error: PROCEDURE attribute conflicts with COMMON attribute in 'a' at (1) bad.for:10:16:
10 | integer*4 a(2)
| 1
Error: GNU Extension: Nonstandard type declaration INTEGER*4 at (1) bad.for:12:13:
12 | data a(1)/123/
| 1
Error: GNU Extension: initialization of common block variable 'a' in
DATA statement at (1)
bad.for:16:16:
16 | integer*4 a(2)
| 1
Error: GNU Extension: Nonstandard type declaration INTEGER*4 at (1) bad.for:18:13:
18 | data a(2)/456/
| 1
Error: GNU Extension: initialization of common block variable 'a' in
DATA statement at (1)
The soso example works fine default.
It is definitely not nice that the compiler and linker silently
drops the initialization of a(2) in the bad example default.
Old G77:
C:\Work\Fortran>g77 soso.for -o soso.exe
C:\Work\Fortran>soso
123 456
C:\Work\Fortran>g77 bad.for -o bad.exe
bad.for: In subroutine `s2':
bad.for:12:
data a(1)/123/
1
bad.for:18: (continued):
data a(2)/456/
2
Common block `m' initialized at (2) already initialized at (1) -- only
one program unit may specify initial values for a particular common block
The soso example works fine default.
I think this way to handle the bad example is rather appropriate.
And an even older Watcom compiler for DOS:
C:\Work\Fortran>wfl soso.for
Open Watcom F77/16 Compile and Link Utility Version 1.9
Portions Copyright (c) 1990-2002 Sybase, Inc. All Rights Reserved.
Source code is available under the Sybase Open Watcom Public License.
See
http://www.openwatcom.org/ for details.
wfc soso.for
Open Watcom FORTRAN 77/16 Optimizing Compiler Version 1.9
Portions Copyright (c) 1984-2002 Sybase, Inc. All Rights Reserved.
Source code is available under the Sybase Open Watcom Public License.
See
http://www.openwatcom.org/ for details.
soso.for: 11 statements, 53 bytes, 4 extensions, 0 warnings, 0 errors
wlink @__wfl__.lnk
Open Watcom Linker Version 1.9
Portions Copyright (c) 1985-2002 Sybase, Inc. All Rights Reserved.
Source code is available under the Sybase Open Watcom Public License.
See
http://www.openwatcom.org/ for details.
loading object files
searching libraries
creating a DOS executable
C:\Work\Fortran>wfl bad.for
Open Watcom F77/16 Compile and Link Utility Version 1.9
Portions Copyright (c) 1990-2002 Sybase, Inc. All Rights Reserved.
Source code is available under the Sybase Open Watcom Public License.
See
http://www.openwatcom.org/ for details.
wfc bad.for
Open Watcom FORTRAN 77/16 Optimizing Compiler Version 1.9
Portions Copyright (c) 1984-2002 Sybase, Inc. All Rights Reserved.
Source code is available under the Sybase Open Watcom Public License.
See
http://www.openwatcom.org/ for details.
bad.for: 17 statements, 59 bytes, 6 extensions, 0 warnings, 0 errors
wlink @__wfl__.lnk
Open Watcom Linker Version 1.9
Portions Copyright (c) 1985-2002 Sybase, Inc. All Rights Reserved.
Source code is available under the Sybase Open Watcom Public License.
See
http://www.openwatcom.org/ for details.
loading object files
searching libraries
creating a DOS executable
(and it produces correct results too for both - I just can't copy paste
from DOSBOX)
Arne
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