Segmentation fault in Fortran derived data type with large array component

Question

Can someone explain why the following code produces a segmentation fault when ND is big (1000000)? Increasing the stack limit does not help.

module parametros_mod
  integer, parameter :: ND = 1000000
end module parametros_mod

module data_mod
  use parametros_mod
  implicit none
  private

  type, public :: data_vec
    real(8) :: f0
    real(8), dimension(ND) :: fvec
  end type data_vec
end module data_mod

!test program
program test
  use parametros_mod
  use data_mod
  implicit none

  type(data_vec) :: v1
  real(8), dimension(ND) :: rv, xv

  rv = 0d0
  rv(2) = 1d0

  v1 = data_vec(1.1d0,rv)
  xv = v1%fvec
  write(*,'(*(f0.4,2x))') xv(1:3)
end program test

Really, someone out there must be teaching the real(8) thing on massive scale. It does not come from good textbooks or tutorials. — Vladimir F Героям слава
– Vladimir F Героям слава, Commented Mar 2, 2017 at 20:37
Your code does not crash for me with gfortran 5.3. If it really does for you I would look at the data_vec(1.1d0,rv) expression, perhaps it causes a temporary object with your compiler. Tell us more about your compiler, compiler flags, operating system. — Vladimir F Героям слава
– Vladimir F Героям слава, Commented Mar 2, 2017 at 20:39

Vladimir F Героям слава · Accepted Answer · 2017-03-02 21:16:50Z

1

I replicated your error, but I had to use larger ND. It is really line

v1 = data_vec(1.1d0,rv)

Probably a temporary object is created on the stack.

You can avoid that by assigning the compnents

v1%f0 = 1.1d0
v1%fvec = rv

answered Mar 2, 2017 at 21:16

Vladimir F Героям слава

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3 Comments

Francisco Over a year ago

Thank you Vladimir, it is working now. I am compiling with GNU Fortran (Debian 4.9.2-10) 4.9.2.

Francisco Over a year ago

I found an alternative solution here in SO in question: What does “ulimit -s unlimited” do?

Vladimir F Героям слава Over a year ago

You said that increasing the stack size didn't help. It's up to you, I like my programs to be robust, because I run them on many different computers and I don't want to care about the stack size on each of them.

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