ExtUtils::XSpp::Exception - Map C++ exceptions to Perl exceptions |
ExtUtils::XSpp::Exception - Map C++ exceptions to Perl exceptions
This class is both the base class for the different exception handling
mechanisms and the container for the global set of exception
mappings from C++ exceptions (indicated by a C++ data type to catch)
to Perl exceptions. The Perl exceptions are implemented via croak()
.
The basic idea is that you can declare the C++ exception types that
you want to handle and how you plan to do so by using the %exception
directive in your XS++ (or better yet, in the XS++ typemap):
// OutOfBoundsException would have been declared // elsewhere as: // // class OutOfBoundsException : public std::exception { // public: // OutOfBoundsException() {} // virtual const char* what() const throw() { // return "You accessed me out of bounds, fool!"; // } // } %exception{outOfBounds}{OutOfBoundsException}{stdmessage};
If you know a function or method may throw MyOutOfBoundsException
s, you
can annotate the declaration in your XS++ as follows:
double get_from_array(unsigned int index) %catch{outOfBounds};
When get_from_array
now throws an OutOfBoundsException
, the user
gets a Perl croak with the message
"Caught exception of type 'OutOfBoundsException': You accessed me out of bounds, fool!"
.
There may be any number of %catch
directives per method.
Note: Why do we assign another name (outOfBounds
) to the
existing OutOfBoundsException
?
Because you may need to catch exceptions of the same C++ type with different
handlers for different methods. You can, in principle, re-use the C++ exception
class name for the exception map name, but that may be confusing to posterity.
Instead of adding %catch
to methods, you may also specify exceptions that
you wish to handle for all methods of a class:
class Foo %catch{SomeException,AnotherException} { ... };
The %catch{Foo,Bar,...}
syntax is shorthand for %catch{Foo} %catch{Bar} ...
.
If there are exceptions to be caught both from the class and attached
to a method directly, the exceptions that are attached to the method only will
be handled first. No single type of exceptions will be handled more than once,
therefore it is safe to use this precedence to re-order the class-global
exception handling for a single method.
If there are no %catch
decorators on a method, exceptions derived
from std::exception
will be caught with a generic stdmessage
handler such as above. Even if there are %catch
clauses for the given method,
all otherwise uncaught exceptions will be caught with a generic error message
for safety.
There are different cases of Perl exceptions that are implemented
as sub-classes of ExtUtils::XSpp::Exception
:
std::exception
and
which provide a char* what()
method that will provide an error message.
The Perl-level error message will include the C++ exception type name
and the exception's what()
message.
e
. Your user supplied code
is expected to propagate the exception to Perl by calling croak().
Syntax:
%exception{myClassyException}{CppException}{object}{PerlClass};
Currently, this means just calling PerlClass->new()
and
then die()ing with that object in $@
. There is no good way to pass
information from the C++ exception object to the Perl object.
Will change in future.
...
(meaning anything).
There is a special exception handler nothing
which is always
available:
int foo() %catch{nothing};
It indicates that the given method (or function) is to handle no exceptions. It squishes any exception handlers that might otherwise be inherited from the method's class.
Creates a new ExtUtils::XSpp::Exception
.
Calls the $self->init(@_)
method after construction.
init()
must be overridden in subclasses.
Unimplemented in this base class, but must be implemented in all actual exception classes.
Generates the catch(){}
block of code for inclusion
in the XS output. First (optional) argument is an integer indicating
the number of spaces to use for the first indentation level.
Given a piece of code and a number of spaces to use for global indentation, indents the code and returns it.
Fetches the C++ type of the exception from the type
attribute and returns it.
Returns the name of the exception.
This is the myException
in %exception{myException}{char*}{handler}
.
Returns the the ExtUtils::XSpp::Node::Type manpage C++ type that is used for this exception.
This is the char*
in %exception{myException}{char*}{handler}
.
Given an ExtUtils::XSpp::Exception
object,
adds this object to the global registry, potentially
overwriting an exception map of the same name that was
in effect before.
Given the XS++ name of the exception map, fetches
the corresponding ExtUtils::XSpp::Exception
object
from the global registry and returns it. Croaks on error.
ExtUtils::XSpp::Exception - Map C++ exceptions to Perl exceptions |