HP aC++/HP C A.06.25 Programmer's Guide

8 Exception Handling
Exception handling provides a standard mechanism for coding responses to runtime
errors or exceptions.
This chapter discusses the following topics:
• “Exception Handling in C++” (page 211)
• “Exception Handling as Defined by the ANSI/ISO C++ International Standard”
(page 212)
• “Basic Exception Handling Example” (page 212)
• “Function Try Block Examples” (page 212)
• “Debugging Exception Handling” (page 213)
• “Performance Considerations” (page 213)
Exception Handling
Exception handling provides a standard mechanism for coding responses to runtime
errors or exceptions. Exception handling is on by default. To turn it off, you must use
the +noeh option.
If your executable throws no exceptions, object files compiled with and without the
+noeh option can be mixed freely. However, in an executable which throws exceptions
(HP aC++ runtime libraries throw exceptions), you must be certain that no exception
is thrown in your application which will unwind through a function compiled without
the exception handling option turned on.
In order to prevent this, the call graph for the program must never have calls from
functions compiled without exception handling to functions compiled with exception
handling (either direct calls or calls made through a callback mechanism). If such calls
do exist, and an exception is thrown, the unwinding can cause:
• Non-destruction of local objects (including compiler generated temporaries).
• Memory leaks when destructors are not executed.
• Runtime errors when no catch clause is found.
Exception Handling in C++
Following is an overview of the elements of C++ exception handling:
• A try block encloses (logically) code that can cause an exception that you want to
catch.
• A catch clause, which immediately follows the try block, handles an exception of
the type that can occur in the try block. The catch clause is the exception handler.
You can have multiple catch clauses associated with a try block.
Exception Handling 211