Search results
Results from the WOW.Com Content Network
The implementation of exception handling in programming languages typically involves a fair amount of support from both a code generator and the runtime system accompanying a compiler. (It was the addition of exception handling to C++ that ended the useful lifetime of the original C++ compiler, Cfront. [18]) Two schemes are most common.
An exception handling mechanism allows the procedure to raise an exception [2] if this precondition is violated, [1] for example if the procedure has been called on an abnormal set of arguments. The exception handling mechanism then handles the exception. [3] The precondition, and the definition of exception, is subjective.
Handling errors in this manner is considered bad practice [1] and an anti-pattern in computer programming. In languages with exception handling support, this practice is called exception swallowing. Errors and exceptions have several purposes:
In a language that supports formal exception handling, a graceful exit may be the final step in the handling of an exception. In other languages graceful exits can be implemented with additional statements at the locations of possible errors.
The Perl mechanism for exception handling uses die to throw an exception when wrapped inside an eval {...}; block. After the eval, the special variable $@ contains the value passed from die. Perl 5.005 added the ability to throw objects as well as strings. This allows better introspection and handling of types of exceptions.
This mechanism enables the automated handling of software errors independent of the application source code and of its developers. It is a direct artifact of the runtime engine paradigm and it enables unique advantages to the software life cycle that were unavailable before.
A key mechanism for exception safety is a finally clause, or similar exception handling syntax, which ensure that certain code is always run when a block is exited, including by exceptions. Several languages have constructs that simplify this, notably using the dispose pattern , named as using , with , or try -with-resources.
A number of languages implement a form of switch statement in exception handling, where if an exception is raised in a block, a separate branch is chosen, depending on the exception. In some cases a default branch, if no exception is raised, is also present. An early example is Modula-3, which use the TRY...