Exception-Handler Syntax
The
try and
except keywords are used to construct a frame-based exception handler. The following
example shows the structure of a
try-
except exception handler.
try {
// guarded body of code
}
except (filter-expression) {
// exception-handler block
}
Note that the
try block and the exception-handler block require braces ({}). Using a
goto statement to jump into the body of a
try block or into an exception-handler block is not permitted. This rule applies
to both
try-
except and
try-
finally statements.
The
try block contains the guarded body of code that the exception handler protects.
A function can have any number of
try-
except statements, and these exception-handling statements can be nested within the
same function or in different functions. If an exception occurs within the
try block, the system takes control and begins the search for an exception
handler. For a detailed description of this search, see
Exception Handling.
The exception handler receives only exceptions that occur within a single
thread. This means that if a
try block contains a call to the
CreateProcess or
CreateThread function, exceptions that occur within the new process or thread are not
dispatched to this handler.
The system evaluates the filter expression of each exception handler guarding
the code in which the exception occurred until either the exception is handled
or there are no more handlers. A filter expression must be evaluated as one of
the three following values.
EXCEPTION_EXECUTE_HANDLER
|
|
| The system transfers control to the exception handler, and execution continues
in the stack frame in which the handler is found.
|
EXCEPTION_CONTINUE_SEARCH
|
|
| The system continues to search for a handler.
|
EXCEPTION_CONTINUE_EXECUTION
|
|
| The system stops its search for a handler and returns control to the point at
which the exception occurred. If the exception is noncontinuable, this results
in a EXCEPTION_NONCONTINUABLE_EXCEPTION exception.
|
The filter expression is evaluated in the context of the function in which the
try-
except statement is located, even though the exception may have occurred in a
different function. This means that the filter expression can access the function's
local variables. Similarly, the exception-handler block can access the local
variables of the function in which it is located.
For more information about filter expressions and filter functions, see
Frame-based Exception Handling.
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