Any attempt to cast a shared pointer to a local per-thread pointer is considered erroneous if the thread component of the shared pointer does not equal the thread number of the referencing thread. This error can arise, even though the program doesn't try to dereference the invalid local pointer. The following example illustrates this situation.

% cat badptr.upc
#include 
#include 

shared int v[THREADS];

int
main ()
{
  int *vp;
  v[MYTHREAD] = MYTHREAD;
  upc_barrier;
  vp = (int *) &v[0];
  if (MYTHREAD == 0)
    printf ("v[0] = %d\n", *vp);
}
% upc -fupc-threads-4 badptr.upc -o badptr
% badptr
badptr: UPC error: Invalid conversion of shared address to local pointer.
Thread does not have affinity to shared address.
v[0] = 0
thread 3 terminated with signal: 'Aborted' Terminated

The error can be corrected by ensuring that the pointer conversion is made only in a valid context.

% cat goodptr.upc
#include 
#include 

shared int v[THREADS];

int
main ()
{
  v[MYTHREAD] = MYTHREAD;
  upc_barrier;
  if (MYTHREAD == 0)
    {
      int *vp = (int *) &v[0];
      printf ("v[0] = %d\n", *vp);
    }
}
% upc -fupc-threads-4 goodptr.upc -o goodptr
% goodptr
v[0] = 0