10.7. C/C++ Arrays in a firstprivate Clause

The following example illustrates the size and value of list items of array or pointer type in a firstprivate clause . The size of new list items is based on the type of the corresponding original list item, as determined by the base language.

In this example:

• The type of A is array of two arrays of two ints.

• The type of B is adjusted to pointer to array of n ints, because it is a function parameter.

• The type of C is adjusted to pointer to int, because it is a function parameter.

• The type of D is array of two arrays of two ints.

• The type of E is array of n arrays of n ints.

Note that B and E involve variable length array types.

The new items of array type are initialized as if each integer element of the original array is assigned to the corresponding element of the new array. Those of pointer type are initialized as if by assignment from the original item to the new item.

//%compiler: clang
//%cflags: -fopenmp

/*
* name: carrays_fpriv.1
* type: C
*/
#include <assert.h>

int A[2][2] = {1, 2, 3, 4};

void f(int n, int B[n][n], int C[])
{
  int D[2][2] = {1, 2, 3, 4};
  int E[n][n];

  assert(n >= 2);
  E[1][1] = 4;

  #pragma omp parallel firstprivate(B, C, D, E)
  {
    assert(sizeof(B) == sizeof(int (*)[n]));
    assert(sizeof(C) == sizeof(int*));
    assert(sizeof(D) == 4 * sizeof(int));
    assert(sizeof(E) == n * n * sizeof(int));

    /* Private B and C have values of original B and C. */
    assert(&B[1][1] == &A[1][1]);
    assert(&C[3] == &A[1][1]);
    assert(D[1][1] == 4);
    assert(E[1][1] == 4);
  }
}

int main() {
  f(2, A, A[0]);
  return 0;
}