CODEWITHSUNDEEP
arrayspointersfortranfortran90intel-fortran
Stano
Stano

Reputation: 11

Fortran array of pointer arrays defined as pointer (bug in ifort 11.1?)

I have one question and one problem (I think they are related).

Question: Can I use in Fortran 90 array of pointer arrays defined as pointer?

type string
  character, pointer :: str(:)
end type

type(string), pointer :: arr(:)

Problem: I have code (see below) for which ifort 11.1 gives segfault in the last write. Other compilers, such as gfortran 4.6.3, ifort 11.1.072, 12.0.1, ..., worked without a problem

You can think about the code as simulation of Python append function.

program test
implicit none

type string
  integer,   pointer :: key
  character, pointer :: str(:)
end type

type(string), pointer :: arr(:), tmp(:)

allocate(arr(1))
allocate(arr(1)%str(1))
arr(1)%str(1) = 'A'
write(6,*) arr(1)%str(1)

! --------------------

tmp => arr
write(6,*) tmp(1)%str(1)

! --------------------

nullify(arr)
allocate(arr(2))
arr(1)%str => tmp(1)%str
write(6,*) arr(1)%str(1)

end program

Expected result is:

A
A
A

ifort 11.1 gives segmentation fault on the last line. Now comes the weird thing. If you comment out declaration of integer in type string you will get the expected result also with ifort 11.1.

Is this compiler problem or am I using non-standard Fortran 90 structures?

Upvotes: 1

Views: 561

Answers (1)

High Performance Mark
High Performance Mark

Reputation: 78316

Your code compiles and executes without a problem using Intel Fortran 13.0.something. Together with your experience with other compilers and compiler versions this does suggest a compiler bug, albeit one that is now corrected.

I'm not entirely sure what the Python append function does, but if you are looking for a Fortran way to make strings whose contents (and lengths) can change dynamically you should seriously consider using the Fortran 2003 automatic allocation features. For example, you could define a string like this:

character(len=:), allocatable :: string1

give it a value like this:

string1 = 'this is string 1'

and give it another value like this:

string1 = 'this is'

or like this

string1 = string1//' more text'

Observe the complete lack of statements allocating the size of string1 or reallocating it.

Upvotes: 2

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