gfortran and equivalence produces internal compiler error

[Rolf Sander]

Hello,

I encountered an internal compiler error with gfortran (Ubuntu
5.4.0-6ubuntu1~16.04.2) and the error message suggests to submit a GCC
bug report:

-----------
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.
-----------

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.

[Matthias Klose (doko)]

(gdb) bt
#0 0x0000000000643a8e in ?? ()
#1 0x0000000000643898 in ?? ()
#2 0x00000000006427f2 in ?? ()
#3 0x0000000000d4e6fe in gfc_generate_function_code(gfc_namespace*) ()
#4 0x0000000000d2c6b6 in gfc_parse_file() ()
#5 0x00000000011e6166 in ?? ()
#6 0x0000000001236373 in ?? ()
#7 0x0000000000d0ca69 in toplev::main(int, char**) ()
#8 0x0000000000d0cdba in main ()

this is fixed in gcc-5 in zesty and in gcc-6.