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C++ Coding Standard

Rule:  ERR#015

Synopsis:Always catch exceptions the caller is not supposed to know about
Severity Level:9
Category:Error Handling


Hidden implementation details is an important property of well written programs, since it gives you the possibility to make changes without affecting the user.

Imagine a hierarchy of libraries where some libraries are implemented on top of other libraries. To be able to change or replace lower level classes without affecting the user, you must catch all exceptions that the user is not supposed to know about. Otherwise an exception of a class unknown to the user could terminate the program or be caught by a handler with a ... parameter list. In either case, nothing can be said about what caused the exception to be thrown. All exceptions that reach the user should be known to the user, since that will make it possible to explain why the exception was thrown and how to prevent it from being thrown. You should try to avoid writing programs that simply crash without any proper indication of what went wrong.