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Name list and Entry Points

 
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hgratt



Joined: 27 Dec 2019
Posts: 2

PostPosted: Fri Dec 27, 2019 8:17 pm    Post subject: Name list and Entry Points Reply with quote

I have some legacy programs that I am using to test ftn95. I'm having trouble getting the combination of subroutine entry points and Namelist data inputs working. I get a runtime error 112.

Below is a simple test program that generates the error. If I use subroutines instead of entry points, it works. I am far from an experienced programmer and would like to know what the issue is. Any insight would be appreciated - i'm sure it's something silly on my part.

Thanks











program test
include 'all.inc'
namelist /STEP/ D1

open(1, file='six.at2')
rewind (1)
read (1, nml=STEP)
print*, d1
call printsubinit
call myprint
print*,d1
end program test

subroutine myprint
include 'all.inc'
namelist /prt/ xy
print*, "test output"
return
cc end

entry printsubinit
cc subroutine printsubinit
cc include 'all.inc'
cc namelist /prt/ xy
print*,'herehere'
rewind (1)
print*,'hereherehere'
read (1, nml=prt)
print*,'999',5*d1
print*,xy
return
end


COMMON /ALL/ d1,xy !include file



&STEP !DATA FILE
D1=.0025 d1=9.
/

&prt
xy=120.
/
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PaulLaidler
Site Admin


Joined: 21 Feb 2005
Posts: 6153
Location: Salford, UK

PostPosted: Sat Dec 28, 2019 11:18 am    Post subject: Reply with quote

I don't have time to check this out at the moment but if at all possible you should avoid entry points in the code.
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mecej4



Joined: 31 Oct 2006
Posts: 1234

PostPosted: Sat Dec 28, 2019 12:24 pm    Post subject: Reply with quote

"hgratt":

Please note that NAMELIST and ENTRY are now used infrequently, and the compiler may still have unreported/not-yet-fixed bugs in how it handles these features of the language. See, for example, the post http://forums.silverfrost.com/viewtopic.php?t=3743 . The bug reported there is still present in the 8.51 compiler.
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LitusSaxonicum



Joined: 23 Aug 2005
Posts: 2067
Location: Yateley, Hants, UK

PostPosted: Sat Dec 28, 2019 3:10 pm    Post subject: Reply with quote

In some respects I have been lucky, as the first compilers I used did not support either NAMELIST or ENTRY, and Iíve therefore not become hooked on either. The code that hgratt posted and described (incidentally, it is a good idea to tag it with Ďcodeí so it stands out) shows how ENTRY is used instead of 2 separate subroutines simply to avoid making declarations twice, as there isnít any shared code. Personally, I would prefer the two subroutines usage, as there are several ways round the lengthy declaration of variables, including:
    Using IMPLICIT type
    Using COMMON
    Using INCLUDE
    Using MODULEs
    Using a subprogram parameter and using IF inside the subprogram

Some of these wonít appeal to everyone, but ENTRY is not actually one of those constructs that are difficult to do without.

As far as NAMELIST goes, it does require that the user has some idea of the variable names used inside the program, which is obvious if one is programming for oneself, but far from obvious if one is programming for others. Indeed, NAMELIST probably means that the program comes with a hefty user manual defining those names. Using a Windows type of interface through the use of (say) ClearWin+ probably means that NAMELIST loses some of its purpose or importance.

Nevertheless, it is always an irritation that something that used to work no longer does so in the interests of 'progress', and especially with Fortran, as one of its strengths is that it handles legacy code!

Eddie
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mecej4



Joined: 31 Oct 2006
Posts: 1234

PostPosted: Sat Dec 28, 2019 3:34 pm    Post subject: Reply with quote

Eddie, your comments are quite apt, but note that the test code also uses a COMMON block to enable some variables to be shared. The presence of COMMON makes it more difficult to use some of the alternatives that you suggested, especially when the same block may have different member names in different declarations of the block.
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hgratt



Joined: 27 Dec 2019
Posts: 2

PostPosted: Sat Dec 28, 2019 7:53 pm    Post subject: Reply with quote

Thanks for the replies. A couple of comments:

1. I'm aware that use of Namelist and Entry points are considered to be a "faux pas" in the age of structured programming. I was just hoping that legacy programs would compile and run with minimal tinkering.

2. The test program did run correctly if I replaced the entry point construct with the appropriate initialization subroutine constructs (the current commented out code). I guess this appears to be the minimum effort mods that need to be made.

Anyway, at this point from the responses, it appears to be a possible compiler issue. Anymore additional insight or conclusions would still be appreciated.

Thanks,
Harvey
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LitusSaxonicum



Joined: 23 Aug 2005
Posts: 2067
Location: Yateley, Hants, UK

PostPosted: Mon Dec 30, 2019 4:09 pm    Post subject: Reply with quote

Mecej4 - the options were a short list. I was talking about using COMMON to shorten the repeat declaration of variables in the multiple SUBROUTINE approach, not that it was something the original post omitted.

If you need to re-write huge chunks of legacy code to get it to run, then one major advantage of Fortran, which is that it does compile legacy code with minimal rewriting is lost. That was all.

Eddie
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