Part 20. Pattern 12. Exceptions

Generation and processing of exceptions using integer types is a bad practice of C++ programming. You should use more informative types for these purposes, for example types derived from the class std::exception. But sometimes you have to deal with a low-quality code like this:

char *ptr1;
char *ptr2;
try {
  try {
    throw ptr2 - ptr1;
  }
  catch (int) {
    std::cout << "catch 1: on x86" << std::endl;
  }
}
catch (ptrdiff_t) {
  std::cout << "catch 2: on x64" << std::endl;
}

You should be very attentive and avoid generation or processing of exceptions using memsize-types because it may result in changes of program logic. To correct this code you may replace “catch (int)” with “catch (ptrdiff_t)”. A more correct way is to use a special class to pass the information about an error that has occurred.

Diagnostic

We have not encountered errors of this type in practice yet but the tool PVS-Studio can detect them. The diagnostic message V115 will be shown when an exception is generated with the help of a memsize-type, while the warning V116 will be generated when a memsize-type is used in catch operator.

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