C166: PAG and POF from Pointers

Information in this article applies to:

• C166 Version 6, or higher

SYMPTOM

I have a function that was initially written for the Tasking Compiler. This function uses specific Tasking extensions that are not available in the ANSI standard:

void TskInit (unsigned int *stk, void (*task) (void), void far *p)  {
  *stk-- = _sof(task);
  *stk-- = _seg(task);

  *stk-- = _pof(p);
  *stk-- = _pag(p);
}

CAUSE

You may convert:

• __sof: into an int cast operation.
• __seg: into an int cast operation with shift.
• __pag/pof: into a standard pointer assignment.

The function below has exactly the same effect and does not need any non ANSI extensions:

void TskInit (unsigned int *stk, void (*task) (void), void far *p)  {
  *stk-- = (unsigned int) task;
  *stk-- = (unsigned int) ((unsigned long) task >> 16);

  *((void far **) stk) = p;
  stk -= 2;
}

Even better would be to define a struct that represents the stack layout of the Task Control Block. However, this might be a bigger change in the system.

MORE INFORMATION

• Refer to Register Usage in the C166 User's Guide.

SEE ALSO

• C166: Where Is the User Stack Located?

Last Reviewed: Thursday, February 25, 2021