Returning error codes from a function

[Dave Jeffery]

  We would like to write a function that returns a pointer to void
 (void *). In this function there are several conditions that can
 occur that would be considered an error. Rather than simply
 returning NULL we would like to return more detailed error information.
 Several ideas have been discussed but one that seems to have the most
 promise is to define several global void pointers and return them.
  Please note that this is in a multi-tasking environment where a global
 error code is not acceptable, and the overhead of passing additional
 parameters is too high.

   void *error1 = "error1";
   void *error2 = "error2";

   void *ourfun(int p1);

   main() {
    ...
    if (ourfun(10) == error1) ...
    ... }

   void *ourfun(int p1) {
    ....
    return error1;
    ...  }

  Our concerns are:
   1. Does this violate ANSI C ?
   2. Is it portable ?

  In your replies, please site where in the ANSI C standard, or any
 other publication, this issue is clarified.

----
 Dave Jeffery           JI8 at psuvm.psu.edu