How to call C++ funtion from Fortran 77 using std::vector as arguments?

Question

I have to replace some Fortran subroutines with C++ functions. Since the literature is poor, I am stuck with a problem like the following one.

My code always throws an error:

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

This is my Fortran code:

  PROGRAM vector_adder
  IMPLICIT NONE

  INTEGER,DIMENSION(3) :: a,b,c
  INTEGER :: i

  !C fill vectors with values
  DO i = 1,3
      a(i) = i
      b(i) = i
  END DO

  CALL ADD_VECTORS(a,b,c)

  WRITE(*,'(I5,I5,I5)') (c(i),i =1,3)

  STOP
  END PROGRAM

A working C code:

void add_vectors_(int (*a)[3], int (*b)[3], int (*c)[3])
{
    for(int i = 0; i<3 ; i++)
    {
        (*c)[i] =(*a)[i] + (*b)[i];
    }
}

And I would like a similar one in C++:

extern "C" void add_vectors_(std::vector<int> *a, std::vector<int> *b, std::vector<int> *c)
{
    for(int i = 0; i<a->size() ; i++)
    {
        (*c)[i] =(*a)[i] + (*b)[i];
    }
}

Answer 1

You are mixing your fortran, C lingo of vector which refers to a collection of ints in contiguous memory location i.e an array with C++'s std::vector. std::vector is a separate container class altogether and needs construction - refer to the documentation