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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 will be 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;
}

This will result results in inconsistent behavior across implementations and possible termination of the program instead of a graceful exit. The implementation-defined default handler performs a default action consistent with a particular implementation. However, this may not be the desired action, and because the behavior is implementation-defined, it is not guaranteed to be the same on all implementations.

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_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;
}

Risk

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Assessment

The TR24731-1 standard indicates that if no constraint handler is set, a default one executes when errors arise. The default handler is implementation-defined and "may cause the program to exit or abort." It is important to understand the behavior of the default handler for all implementations being used and replace it if the behavior is inappropriate for the application.

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