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Next: When to throw an exception Up: Note 190: Exceptions Changes for AIPS++ Previous: Note 190: Exceptions Changes for AIPS++

Exception mechanism

The C++ exception mechanism provides three features:

1.: Transfer of control between the point in the program where the the exception is thrown, and where it is caught.
2.: Transfoer of information between the ``thrown'' and ``caught'' locations. The information which is transferred can be arbitrary, since any object can be thrown. Note that a copy of the object is thrown.
3.: Destruction of automatic objects.

The differences between the AIPS++ exception emulation and the standard C++ mechanism are as follows:

1.: Only classes that follow certain rules¹ may be thrown using the AIPS++ emulation.
2.: Standard exceptions allow ``any'' exception to be caught with a single catch statement (using catch(...)).
3.: Only classes derived from a special base class are destroyed by the AIPS++ exception emulation.
4.: The syntax of the AIPS++ emulation is somewhat different. For example, catch clauses must end with end_try. These differences can be hidden by a macro.
5.: AIPS++ cannot rethrow exceptions.
6.: AIPS++ does not support exception specifications.
7.: AIPS++ exceptions contain the line number and source file of the location from which they were thrown.

Next: When to throw an exception Up: Note 190: Exceptions Changes for AIPS++ Previous: Note 190: Exceptions Changes for AIPS++