1ExtUtils::XSpp::ExceptiUosne(r3)Contributed Perl DocumenEtxattUitoinls::XSpp::Exception(3)
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6 ExtUtils::XSpp::Exception - Map C++ exceptions to Perl exceptions
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9 This class is both the base class for the different exception handling
10 mechanisms and the container for the global set of exception mappings
11 from C++ exceptions (indicated by a C++ data type to catch) to Perl
12 exceptions. The Perl exceptions are implemented via "croak()".
13 The basic idea is that you can declare the C++ exception types that you
15 want to handle and how you plan to do so by using the %exception
16 directive in your XS++ (or better yet, in the XS++ typemap):
17 // OutOfBoundsException would have been declared
19 // elsewhere as:
20 //
21 // class OutOfBoundsException : public std::exception {
22 // public:
23 // OutOfBoundsException() {}
24 // virtual const char* what() const throw() {
25 // return "You accessed me out of bounds, fool!";
26 // }
27 // }
28 %exception{outOfBounds}{OutOfBoundsException}{stdmessage};
30 If you know a function or method may throw "MyOutOfBoundsException"s,
32 you can annotate the declaration in your XS++ as follows:
33 double get_from_array(unsigned int index)
35 %catch{outOfBounds};
36 When "get_from_array" now throws an "OutOfBoundsException", the user
38 gets a Perl croak with the message "Caught exception of type
39 'OutOfBoundsException': You accessed me out of bounds, fool!". There
40 may be any number of %catch directives per method.
41 Note: Why do we assign another name ("outOfBounds") to the existing
43 "OutOfBoundsException"? Because you may need to catch exceptions of
44 the same C++ type with different handlers for different methods. You
45 can, in principle, re-use the C++ exception class name for the
46 exception map name, but that may be confusing to posterity.
47 Instead of adding %catch to methods, you may also specify exceptions
49 that you wish to handle for all methods of a class:
50 class Foo %catch{SomeException,AnotherException} {
52 ...
53 };
54 The %catch{Foo,Bar,...} syntax is shorthand for "%catch{Foo}
56 %catch{Bar} ...". If there are exceptions to be caught both from the
57 class and attached to a method directly, the exceptions that are
58 attached to the method only will be handled first. No single type of
59 exceptions will be handled more than once, therefore it is safe to use
60 this precedence to re-order the class-global exception handling for a
61 single method.
62 If there are no %catch decorators on a method, exceptions derived from
64 "std::exception" will be caught with a generic "stdmessage" handler
65 such as above. Even if there are %catch clauses for the given method,
66 all otherwise uncaught exceptions will be caught with a generic error
67 message for safety.
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70 There are different cases of Perl exceptions that are implemented as
71 sub-classes of "ExtUtils::XSpp::Exception":
72 ExtUtils::XSpp::Exception::simple
74 implements the most general case of simply throwing a generic error
75 message that includes the name of the C++ exception type.
76 ExtUtils::XSpp::Exception::stdmessage
78 handles C++ exceptions that are derived from "std::exception" and
79 which provide a "char* what()" method that will provide an error
80 message. The Perl-level error message will include the C++ exception
81 type name and the exception's "what()" message.
82 ExtUtils::XSpp::Exception::code
84 allows the user to supply custom C/C++/XS code that will be included
85 in the exception handler verbatim. The code has access to the
86 exception object as the variable "e". Your user supplied code is
87 expected to propagate the exception to Perl by calling croak().
88 ExtUtils::XSpp::Exception::object
90 maps C++ exceptions to throwing an instance of some Perl exception
91 class.
92 Syntax:
94 %exception{myClassyException}{CppException}{object}{PerlClass};
96 Currently, this means just calling "PerlClass->new()" and then
98 die()ing with that object in $@. There is no good way to pass
99 information from the C++ exception object to the Perl object. Will
100 change in future.
101 ExtUtils::XSpp::Exception::unknown
103 is the default exception handler that is added to the list of
104 handlers automatically during code generation. It simply throws an
105 entirely unspecific error and catches the type "..." (meaning
106 anything).
107 There is a special exception handler "nothing" which is always
109 available:
110 int foo() %catch{nothing};
112 It indicates that the given method (or function) is to handle no
114 exceptions. It squishes any exception handlers that might otherwise be
115 inherited from the method's class.
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118 new
119 Creates a new "ExtUtils::XSpp::Exception".
120 Calls the "$self->init(@_)" method after construction. "init()" must
122 be overridden in subclasses.
123 handler_code
125 Unimplemented in this base class, but must be implemented in all actual
126 exception classes.
127 Generates the "catch(){}" block of code for inclusion in the XS output.
129 First (optional) argument is an integer indicating the number of spaces
130 to use for the first indentation level.
131 indent_code
133 Given a piece of code and a number of spaces to use for global
134 indentation, indents the code and returns it.
135 cpp_type
137 Fetches the C++ type of the exception from the "type" attribute and
138 returns it.
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141 name
142 Returns the name of the exception. This is the "myException" in
143 %exception{myException}{char*}{handler}.
144 type
146 Returns the ExtUtils::XSpp::Node::Type C++ type that is used for this
147 exception. This is the "char*" in
148 %exception{myException}{char*}{handler}.
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151 add_exception
152 Given an "ExtUtils::XSpp::Exception" object, adds this object to the
153 global registry, potentially overwriting an exception map of the same
154 name that was in effect before.
155 get_exception_for_name
157 Given the XS++ name of the exception map, fetches the corresponding
158 "ExtUtils::XSpp::Exception" object from the global registry and returns
159 it. Croaks on error.
160perl v5.34.0 2021-07-22 ExtUtils::XSpp::Exception(3)