Previous: Invoking Functions Through Global Pointers Up: Global Pointers Next: Pitfalls

Casting Global Pointers

Because of this danger, CC++ will not implicitly cast a global pointer to a local pointer. If the global pointer really references memory on the current processor object, then an explicit cast can be used.

{
  int *global gpi;
  int* pi= (int *)gpi;  // Think Carefully Before Using!
}

An explicit cast must only be used when it is certain that the global pointer references memory in the local processor object. A run-time error results if this is not the case.

Local pointers are implicitly, and can also be explicitly, cast into global pointers. Here are the four possibilities:

{
  int* pi;
  int *global gpi = pi;   // Implicit local-to-global cast OK
  int *global gpi2 = (int *global)pi;   // Explicit local-to-global cast OK
  pi = gpi;   // Implicit global-to-local cast COMPILE-TIME ERROR
  pi = (int *)gpi;   // Explicit global-to-local cast POSSIBLE RUN-TIME ERROR
}

In this example, the explicit global-to-local cast would not be an error, since we initialized gpi using the local pointer pi!