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diff --git a/libs/python/doc/v2/errors.html b/libs/python/doc/v2/errors.html new file mode 100644 index 000000000..69a3cf570 --- /dev/null +++ b/libs/python/doc/v2/errors.html @@ -0,0 +1,289 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> + +<!-- Copyright David Abrahams 2006. Distributed under the Boost --> +<!-- Software License, Version 1.0. (See accompanying --> +<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> +<html> + <head> + <meta name="generator" content= + "HTML Tidy for Windows (vers 1st August 2002), see www.w3.org"> + <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> + <link rel="stylesheet" type="text/css" href="../boost.css"> + + <title>Boost.Python - <boost/python/errors.hpp></title> + </head> + + <body> + <table border="0" cellpadding="7" cellspacing="0" width="100%" summary= + "header"> + <tr> + <td valign="top" width="300"> + <h3><a href="../../../../index.htm"><img height="86" width="277" + alt="C++ Boost" src="../../../../boost.png" border="0"></a></h3> + </td> + + <td valign="top"> + <h1 align="center"><a href="../index.html">Boost.Python</a></h1> + + <h2 align="center">Header <boost/python/errors.hpp></h2> + </td> + </tr> + </table> + <hr> + + <h2>Contents</h2> + + <dl class="page-index"> + <dt><a href="#introduction">Introduction</a></dt> + + <dt><a href="#classes">Classes</a></dt> + + <dd> + <dl class="page-index"> + <dt><a href="#error_already_set-spec">Class + <code>error_already_set</code></a></dt> + + <dd> + <dl class="page-index"> + <dt><a href="#error_already_set-spec-synopsis">Class + <code>error_already_set</code> synopsis</a></dt> + </dl> + </dd> + </dl> + </dd> + + <dt><a href="#functions">Functions</a></dt> + + <dd> + <dl class="page-index"> + <dt><a href="#handle_exception-spec">handle_exception</a></dt> + + <dt><a href="#expect_non_null-spec">expect_non_null</a></dt> + + <dt><a href= + "#throw_error_already_set-spec">throw_error_already_set</a></dt> + </dl> + </dd> + + <dt><a href="#examples">Examples</a></dt> + </dl> + <hr> + + <h2><a name="introduction"></a>Introduction</h2> + + <p><code><boost/python/errors.hpp></code> provides types and + functions for managing and translating between Python and C++ exceptions. + This is relatively low-level functionality that is mostly used internally + by Boost.Python. Users should seldom need it.</p> + + <h2><a name="classes"></a>Classes</h2> + + <h3><a name="error_already_set-spec"></a>Class + <code>error_already_set</code></h3> + + <p><code>error_already_set</code> is an exception type which can be + thrown to indicate that a Python error has occurred. If thrown, the + precondition is that <a href= + "http://www.python.org/doc/2.2/api/exceptionHandling.html#l2h-71">PyErr_Occurred()</a> + returns a value convertible to <code>true</code>. Portable code shouldn't + throw this exception type directly, but should instead use <code><a href= + "#throw_error_already_set-spec">throw_error_already_set</a>()</code>, + below.</p> + + <h4><a name="error_already_set-spec-synopsis"></a>Class error_already_set + synopsis</h4> +<pre> +namespace boost { namespace python +{ + class error_already_set {}; +}} +</pre> + + <h2><a name="functions"></a>Functions</h2> +<pre> +<a name= +"handle_exception-spec">template <class T> bool handle_exception</a>(T f) throw(); + +void handle_exception() throw(); +</pre> + + <dl class="handle_exception-semantics"> + <dt><b>Requires:</b> The first form requires that the expression + <code><a href= + "../../../../doc/html/functionN.html">function0</a><void>(f)</code> + is valid. The second form requires that a C++ exception is currently + being handled (see section 15.1 in the C++ standard).</dt> + + <dt><b>Effects:</b> The first form calls <code>f()</code> inside a + <code>try</code> block which first attempts to use all registered <a + href="exception_translator.html">exception translators</a>. If none of + those translates the exception, the <code>catch</code> clauses then set + an appropriate Python exception for the C++ exception caught, returning + <code>true</code> if an exception was thrown, <code>false</code> + otherwise. The second form passes a function which rethrows the + exception currently being handled to the first form.</dt> + + <dt><b>Postconditions:</b> No exception is being handled</dt> + + <dt><b>Throws:</b> nothing</dt> + + <dt><b>Rationale:</b> At inter-language boundaries it is important to + ensure that no C++ exceptions escape, since the calling language + usually doesn't have the equipment necessary to properly unwind the + stack. Use <code>handle_exception</code> to manage exception + translation whenever your C++ code is called directly from the Python + API. This is done for you automatically by the usual function wrapping + facilities: <code><a href= + "make_function.html#make_function-spec">make_function</a>()</code>, + <code><a href= + "make_function.html#make_constructor-spec">make_constructor</a>()</code>, + <code><a href="def.html#class_-spec-modifiers">def</a>()</code> and <code><a href= + "class.html#def-spec">class_::def</a>()</code>. The second form can be + more convenient to use (see the <a href="#examples">example</a> below), + but various compilers have problems when exceptions are rethrown from + within an enclosing <code>try</code> block.</dt> + </dl> +<pre> +<a name= +"expect_non_null-spec">template <class T> T* expect_non_null(T* x);</a> +</pre> + + <dl class="expect_non_null-semantics"> + <dt><b>Returns:</b> <code>x</code></dt> + + <dt><b>Throws:</b> <code><a href= + "#error_already_set-spec">error_already_set</a>()</code> iff <code>x == + 0</code>.</dt> + + <dt><b>Rationale:</b> Simplifies error-handling when calling functions + in the <a href="http://www.python.org/doc/2.2/api/api.html">Python/C + API</a> which return 0 on error.</dt> + </dl> +<pre> +<a name="throw_error_already_set-spec">void throw_error_already_set();</a> +</pre> + + <dl class="throw_error_already_set-semantics"> + <dt><b>Effects:</b> <code>throw <a href= + "#error_already_set-spec">error_already_set</a>();</code></dt> + </dl> + + <dl> + <dt><b>Rationale:</b> Many platforms and compilers are not able to + consistently catch exceptions thrown across shared library boundaries. + Using this function from the Boost.Python library ensures that the + appropriate <code>catch</code> block in <code><a href= + "#handle_exception-spec">handle_exception</a>()</code> can catch the + exception.</dt> + </dl> + + <h2><a name="examples"></a>Examples</h2> +<pre> +#include <string> +#include <boost/python/errors.hpp> +#include <boost/python/object.hpp> +#include <boost/python/handle.hpp> + +// Returns a std::string which has the same value as obj's "__name__" +// attribute. +std::string get_name(boost::python::object obj) +{ + // throws if there's no __name__ attribute + PyObject* p = boost::python::expect_non_null( + PyObject_GetAttrString(obj.ptr(), "__name__")); + + char const* s = PyString_AsString(p); + if (s != 0) + Py_DECREF(p); + + // throws if it's not a Python string + std::string result( + boost::python::expect_non_null( + PyString_AsString(p))); + + Py_DECREF(p); // Done with p + + return result; +} + +// +// Demonstrate form 1 of handle_exception +// + +// Place into result a Python Int object whose value is 1 if a and b have +// identical "__name__" attributes, 0 otherwise. +void same_name_impl(PyObject*& result, boost::python::object a, boost::python::object b) +{ + result = PyInt_FromLong( + get_name(a) == get_name(a2)); +} + +object borrowed_object(PyObject* p) +{ + return boost::python::object( + boost::python::handle<>( + boost::python::borrowed(a1))); +} + +// This is an example Python 'C' API interface function +extern "C" PyObject* +same_name(PyObject* args, PyObject* keywords) +{ + PyObject* a1; + PyObject* a2; + PyObject* result = 0; + + if (!PyArg_ParseTuple(args, const_cast<char*>("OO"), &a1, &a2)) + return 0; + + // Use boost::bind to make an object compatible with + // boost::Function0<void> + if (boost::python::handle_exception( + boost::bind<void>(same_name_impl, boost::ref(result), borrowed_object(a1), borrowed_object(a2)))) + { + // an exception was thrown; the Python error was set by + // handle_exception() + return 0; + } + + return result; +} + +// +// Demonstrate form 2 of handle_exception. Not well-supported by all +// compilers. +// +extern "C" PyObject* +same_name2(PyObject* args, PyObject* keywords) +{ + PyObject* a1; + PyObject* a2; + PyObject* result = 0; + + if (!PyArg_ParseTuple(args, const_cast<char*>("OO"), &a1, &a2)) + return 0; + + try { + return PyInt_FromLong( + get_name(borrowed_object(a1)) == get_name(borrowed_object(a2))); + } + catch(...) + { + // If an exception was thrown, translate it to Python + boost::python::handle_exception(); + return 0; + } +} +</pre> + + <p>Revised + <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> + 13 November, 2002 + <!--webbot bot="Timestamp" endspan i-checksum="39359" --> + </p> + + <p><i>© Copyright <a href= + "http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p> + </body> +</html> + |