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Exception handling is available in PowerBuilder versions 8.0 and above. TRY // Normal execution path CATCH (ExampleException ee) // deal with the ExampleException FINALLY // This optional section is executed upon termination of any of the try or catch blocks above END TRY
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.
The first hardware exception handling was found in the UNIVAC I from 1951. Arithmetic overflow executed two instructions at address 0 which could transfer control or fix up the result. [16] Software exception handling developed in the 1960s and 1970s. Exception handling was subsequently widely adopted by many programming languages from the ...
Microsoft supports SEH as a programming technique at the compiler level only. MS Visual C++ compiler features three non-standard keywords: __try, __except and __finally — for this purpose. Other exception handling aspects are backed by a number of Win32 API functions, [2] for example, RaiseException to raise SEH exceptions manually.
try {// do something} catch (Exception ex) {// maybe do some local handling of the exception throw new Exception (ex. Message ); } A better way of rethrowing exceptions without losing information is to throw the original exception from the catch clause:
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.
Via C++'s influence, catch is the keyword reserved for declaring a pattern-matching exception handler in other languages popular today, like Java or C#. Some other languages like Ada use the keyword exception to introduce an exception handler and then may even employ a different keyword ( when in Ada) for the pattern matching.
In a more modern-looking example, the usual "try" block would be implemented as a setjmp (with some preparation code for multilevel jumps, as seen in first), the "throw" as longjmp with the optional parameter as the exception, and the "catch" as the "else" block under "try".