gfortran and equivalence produces internal compiler error

[Rolf Sander <rolf dot sander at mpic dot de>]

Hello,

I encountered an internal compiler error with gfortran (Ubuntu
5.4.0-6ubuntu1~16.04.2). I was able to boil down the problem to the
following simple code:

-----------
MODULE test_equivalence
  REAL, PRIVATE, DIMENSION(100) :: array1
  REAL, PRIVATE, DIMENSION(100) :: array2
  EQUIVALENCE(array1(1),array2(1))
END MODULE test_equivalence

MODULE mymodule
  USE test_equivalence
  ! declare a local variable with the same name as the (private!)
  ! variable in module test_equivalence:
  REAL, DIMENSION(:), ALLOCATABLE :: array1
END MODULE mymodule

PROGRAM test
  USE mymodule
END PROGRAM test
-----------

AFAICS, this code is correct Fortran90. The private arrays in MODULE
test_equivalence should be separate from those in MODULE mymodule.
However, it seems that gfortran turns array1 into a public variable
because of the EQUIVALENCE statement.

Asking a colleague, I was told that the bug also occurs in version 6.2.0
but not in 4.3.4, 4.8.1, and 4.9.4.

The error message was:

-----------
gfortran gfortran_test_equivalence.f90
gfortran_test_equivalence.f90:14:0:

 PROGRAM test
 1
internal compiler error: Segmentation fault
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-5/README.Bugs> for instructions.
-----------

     Best regards
            Rolf

--
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  Rolf Sander                              phone: [+49] 6131/305-4610
  Max-Planck Institute of Chemistry        email: rolf.sander@mpic.de
  PO Box 3060, 55020 Mainz, Germany     homepage: www.rolf-sander.net
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