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Character string is lost

 
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simon



Joined: 05 Jul 2006
Posts: 276

PostPosted: Mon Nov 11, 2024 8:49 pm    Post subject: Character string is lost Reply with quote

I have what seems to be an impossible-to-report problem with a character string getting lost in the 64-bit version! The core of the problem looks something like the following:

Code:
Use m, Only: c2 ! c2 is a character string
Character(Len=16) :: c1
Write ( Unit=c1, Fmt='(A)' ) c2
c1 = c1 ! bug is avoided with this line, as long as this comment is deleted!
Print * c1


I recognise that the above is incomplete code, so it cannot be tested. But I don't know where to begin to start to create an example to illustrate this because the bug does not occur when (a) compiling in 32-bit, (b) adding useless lines like line 4. Even more perplexing, the problem reappears when adding a comment to line 4, and it can also be made to disappear if I delete code that is never even called. The full code is about 160,000 lines. I am happy to try to forward that to Paul if diagnosing this problem does not look like a massive task.
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PaulLaidler
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Joined: 21 Feb 2005
Posts: 8067
Location: Salford, UK

PostPosted: Tue Nov 12, 2024 8:47 am    Post subject: Reply with quote

Simon

I have not seen UNIT=<character variable> before. Is that legal? It is not faulted by FTN95 but perhaps it should be.
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simon



Joined: 05 Jul 2006
Posts: 276

PostPosted: Wed Nov 13, 2024 9:10 pm    Post subject: Reply with quote

Hi Paul,
I've been using Unit=character for years, actually probably decades.
Actually, in this case, I don't think it is integral to the problem I am experiencing since I have other examples that do not use this construct anyway. But, yes, it is probably worth checking how FTN95 handles it. I am uncertain of what the Fortran standard is, but my understanding is that Unit becomes a negative number when it is using an internal file. But it may well be illegal to attempt to pass the character explicitly as the Unit number. If anybody knows I would be happy to hear.
Simon
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PaulLaidler
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Joined: 21 Feb 2005
Posts: 8067
Location: Salford, UK

PostPosted: Thu Nov 14, 2024 8:41 am    Post subject: Reply with quote

Simon

Ah yes. I did not recognise it as an internal write statement.

Have you looked at the point of failure using the debugger?
Have you tried omitting the ONLY in the USE statement?
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simon



Joined: 05 Jul 2006
Posts: 276

PostPosted: Sat Nov 16, 2024 1:24 am    Post subject: Reply with quote

Hi Paul,
Unfortunately, if I try to compile using /DEBUG /CHECK, I get the following error somewhere else in the program:
Quote:
AMD backend failure:Failed to do register-memory emit for MOV_Q at ...

in each case at a Subroutine declaration. Plus I get some Internal compiler errors, again at some Subroutine declarations. None of these problems occur when compiling without those options, nor do they occur when compiling in 32-bit, with or without.
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PaulLaidler
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Joined: 21 Feb 2005
Posts: 8067
Location: Salford, UK

PostPosted: Sat Nov 16, 2024 8:58 am    Post subject: Reply with quote

Simon

1) Please send a simple program that illustrates the /64 /CHECK failure. This is probably something that we need to fix.

2) Try using /DEBUG on its own. That might help you to work out what is going wrong.
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simon



Joined: 05 Jul 2006
Posts: 276

PostPosted: Sat Nov 16, 2024 5:32 pm    Post subject: Reply with quote

Hi Paul,
I will try to send a simple program, but I estimate it will take more than a full day's work, so I can't promise to do it soon.
If I remove /CHECK, then I no longer et compilation errors. and some of the runtime errors go away. When I get some free time, I will try to isolate all these issues ...
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mecej4



Joined: 31 Oct 2006
Posts: 1898

PostPosted: Tue Nov 19, 2024 4:26 am    Post subject: Reply with quote

Here are portions of F2008 that pertain:
Quote:
F2008:
9.6.2R913: io-control-spec is UNIT = io-unit OR ...
9.5.1: R901: io-unit is file-unit-number OR * OR internal-file-variable

Here is the source of a modified version of the test program that runs correctly with the 9.05 version of FTN95
Code:

module m
character(12) :: c2 = 'String c2xyz'
end module

program buggy
Use m, Only: c2 ! c2 is a character string
Character(Len=16) :: c1
Write ( Unit=c1, Fmt='(A)' ) c2
Print *, c1
end program
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simon



Joined: 05 Jul 2006
Posts: 276

PostPosted: Tue Nov 19, 2024 5:37 pm    Post subject: Reply with quote

Thanks for the confirmation. It appears that my partial code was legal, so I'll have to try and find a way to isolate the problem.
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