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Kenneth_Smith
Joined: 18 May 2012
Posts: 801
Location: Hamilton, Lanarkshire, Scotland.
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 Posted: Thu Oct 10, 2024 12:11 pm Post subject: Puzzle |
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This is not a bug report, since I cannot determine what a standard conforming compiler should actually do with this code. So it's a puzzle for those that like that kind of thing.
| Code: | module kind_mod
implicit none
integer, parameter :: dp = kind(1.d0)
end module kind_mod
module x_mod
use kind_mod
implicit none
real(dp) :: a = 1.d0
end module x_mod
module y_mod
use x_mod
implicit none
private
public b ! Only b is public, not clear to me if a from x_mod or dp from kind_mod
! should be visible from the main program that uses y_mod
real(dp) :: b = 2.d0
end module y_mod
program main
use y_mod
print*, a ! FTN95 prints the correct value, is this correct?
print*, b
print*, dp ! FTN95 prints the correct value, is this correct?
end program main
! AI analysis
! Visibility of a:
! a is defined in x_mod and x_mod is used in y_mod. However, because y_mod declares private,
! everything in x_mod (including a) should be private unless explicitly made public in y_mod.
! Since a is not listed as public, it is not visible in main.
! Attempting to print a should cause a compilation error.
!
! Visibility of b:
! b is explicitly made public in y_mod, so it is visible in main and should print the value
! of 2.0.
!
! Visibility of dp:
! dp is defined in kind_mod and is used by x_mod. x_mod is used by y_mod. While dp is
! publicly accessible in kind_mod, it is not made private anywhere. Since y_mod does not
! explicitly hide it, dp should be visible in main and should print the kind value for
! double precision, which is typically 8.
!
! If the compiler adheres strictly to the Fortran standard: Attempting to access a would
! result in a compilation error, and the program would not compile due to a being private.
! |
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PaulLaidler
Site Admin
Joined: 21 Feb 2005
Posts: 8184
Location: Salford, UK
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| Posted: Thu Oct 10, 2024 2:21 pm Post subject: |
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Ken
If "implicit none" is added to the main program, FTN95 ought to fault the use of the variables a and dp.
It fails in this respect and I will note this as a bug that needs fixing. |
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Kenneth_Smith
Joined: 18 May 2012
Posts: 801
Location: Hamilton, Lanarkshire, Scotland.
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| Posted: Thu Oct 10, 2024 8:00 pm Post subject: |
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| Paul, Thanks for clearing this up. It was the failure of "IMPLICIT NONE" which caused the problem in the larger program I was looking at. The AI critique of simple example simply added to my confusion. |
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mecej4
Joined: 31 Oct 2006
Posts: 1899
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| Posted: Fri Oct 11, 2024 12:02 am Post subject: |
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Thanks, Kenneth, for this nice puzzling program. With these lines for the main program:
| Code: | program main
use x_mod, only : a
use y_mod
use kind_mod
implicit none
print*, a ! FTN95 prints the correct value, is this correct?
print*, b
print*, dp ! FTN95 prints the correct value, is this correct?
end program main |
The modified code works on Windows 11 with the current Intel IFX compiler, NAG 7219 and GFortran 11.4. |
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Kenneth_Smith
Joined: 18 May 2012
Posts: 801
Location: Hamilton, Lanarkshire, Scotland.
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| Posted: Sat Oct 12, 2024 5:21 pm Post subject: |
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| mecej4, thanks for taking the time to look at this. |
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PaulLaidler
Site Admin
Joined: 21 Feb 2005
Posts: 8184
Location: Salford, UK
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| Posted: Fri Jan 31, 2025 8:07 am Post subject: |
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| This bug has now been fixed for the next release of FTN95. |
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