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In this noncompliant code example, the strcpy_s() function is called, but no runtime-constraint handler has been explicitly registered. As a result, the implementation-defined default handler is called on a runtime error.

errno_t function(char *dst1, size_t size){
  char src1[100] = "hello";

  if (strcpy_s(dst1, size, src1) != 0) {
    return -1;
  }
  /* ... */
  return 0;
}

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This compliant solution explicitly installs a runtime constraint handler by invoking the set_constraint_handler_s() function. This would typically be performed during system initialization and before any functions that used the mechanism were invoked.

constraint_handler_t handle_errors(void) {
  /* Handle runtime constraint error */
}

/*...*/

set_constraint_handler_s(handle_errors);

/*...*/

/* Returns zero on success */
errno_t function(char *dst1, size_t size){
  char src1[100] = "hello";

  if (strcpy_s(dst1, size, src1) != 0) {
    return -1;
  }
  /* ... */
  return 0;
}

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Although the ISO/IEC TR 24731-1 functions were created by Microsoft, currently available versions of Microsoft Visual Studio do not support the same interface defined by the technical report for installing runtime constraint handlers. Visual Studio calls these functions "invalid parameter handlers," and they are installed by calling the _set_invalid_parameter_handler() function. The signature of the handler is also significantly different.

_invalid_parameter_handler handle_errors(
   const wchar_t* expression,
   const wchar_t* function,
   const wchar_t* file,
   unsigned int line,
   uintptr_t pReserved
) {
  /* Handle invalid parameter */
}

/*...*/

_set_invalid_parameter_handler(handle_errors)

/*...*/

errno_t function(char *dst1, size_t size) {
  char src1[100] = "hello";

  if (strcpy_s(dst1, size, src1) != 0) {
    return -1;
  }
  /* ...  */
  return 0;
}

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