forked from boostorg/utility
Compare commits
15 Commits
svn-branch
...
svn-branch
Author | SHA1 | Date | |
---|---|---|---|
6032348b4c | |||
3279399fe3 | |||
87875cadda | |||
c58748cfd9 | |||
58bb88d4bd | |||
11d50ecb9f | |||
636283d7c2 | |||
1df0bf80bc | |||
71e78a0081 | |||
f7e4b0e399 | |||
fb1d2effef | |||
94b91e8c92 | |||
a4b8043e68 | |||
b4a08fc80e | |||
9da96d9737 |
74
assert.html
74
assert.html
@ -17,36 +17,89 @@
|
||||
<td colspan="2" height="64"> </td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
<a href="#BOOST_ASSERT">BOOST_ASSERT</a><br>
|
||||
<a href="#BOOST_ASSERT_MSG">BOOST_ASSERT_MSG</a><br>
|
||||
<a href="#BOOST_VERIFY">BOOST_VERIFY</a></p>
|
||||
|
||||
<h2><a name="BOOST_ASSERT">BOOST_ASSERT</a></h2>
|
||||
<p>
|
||||
The header <STRONG><boost/assert.hpp></STRONG> defines the macro <b>BOOST_ASSERT</b>,
|
||||
which is similar to the standard <STRONG>assert</STRONG> macro defined in <STRONG><cassert></STRONG>.
|
||||
The macro is intended to be used in Boost libraries.
|
||||
The macro is intended to be used in both Boost libraries and user
|
||||
code.
|
||||
</p>
|
||||
<P>By default, <tt>BOOST_ASSERT(expr)</tt> is equivalent to <tt>assert(expr)</tt>.</P>
|
||||
<P>When the macro <STRONG>BOOST_DISABLE_ASSERTS</STRONG> is defined when <STRONG><boost/assert.hpp></STRONG>
|
||||
<P>If the macro <STRONG>BOOST_DISABLE_ASSERTS</STRONG> is defined when <STRONG><boost/assert.hpp></STRONG>
|
||||
is included, <tt>BOOST_ASSERT(expr)</tt> is defined as <tt>((void)0)</tt>. This
|
||||
allows users to selectively disable <STRONG>BOOST_ASSERT</STRONG> without
|
||||
affecting the definition of the standard <STRONG>assert</STRONG>.</P>
|
||||
<P>When the macro <STRONG>BOOST_ENABLE_ASSERT_HANDLER</STRONG> is defined when <STRONG><boost/assert.hpp></STRONG>
|
||||
<P>If the macro <STRONG>BOOST_ENABLE_ASSERT_HANDLER</STRONG> is defined when <STRONG><boost/assert.hpp></STRONG>
|
||||
is included, <tt>BOOST_ASSERT(expr)</tt> evaluates <b>expr</b> and, if the
|
||||
result is false, evaluates the expression</P>
|
||||
<blockquote>
|
||||
<P><tt>::boost::assertion_failed(#expr, <a href="current_function.html">BOOST_CURRENT_FUNCTION</a>,
|
||||
__FILE__, __LINE__)</tt></P>
|
||||
</blockquote>
|
||||
<P><STRONG>assertion_failed</STRONG> is declared in <STRONG><boost/assert.hpp></STRONG>
|
||||
as</P>
|
||||
<pre>
|
||||
namespace boost
|
||||
<blockquote>
|
||||
<pre>namespace boost
|
||||
{
|
||||
|
||||
void assertion_failed(char const * expr, char const * function, char const * file, long line);
|
||||
|
||||
void assertion_failed(char const * expr, char const * function, char const * file, long line);
|
||||
}
|
||||
</pre>
|
||||
</blockquote>
|
||||
<p>but it is never defined. The user is expected to supply an appropriate
|
||||
definition.</p>
|
||||
<P>As is the case with <STRONG><cassert></STRONG>, <STRONG><boost/assert.hpp></STRONG>
|
||||
can be included multiple times in a single translation unit. <STRONG>BOOST_ASSERT</STRONG>
|
||||
will be redefined each time as specified above.</P>
|
||||
|
||||
<h2><a name="BOOST_ASSERT_MSG">BOOST_ASSERT_MSG</a></h2>
|
||||
<p>
|
||||
The header <STRONG><boost/assert.hpp></STRONG> defines the macro <b>BOOST_ASSERT_MSG</b>,
|
||||
which is similar to the standard <STRONG>assert</STRONG> macro defined in <STRONG><cassert></STRONG>,
|
||||
but with an additional macro parameter supplying an error message. The macro is intended to be used in both Boost libraries
|
||||
and user code.
|
||||
</p>
|
||||
<P> <tt>BOOST_ASSERT_MSG(expr, msg)</tt> is equivalent to <code>
|
||||
((void)0)</code> if <b>BOOST_DISABLE_ASSERTS</b> or <b>NDEBUG</b> are
|
||||
defined or <code>expr</code> evaluates to <code>true</code>. If those
|
||||
macros and <STRONG>BOOST_ENABLE_ASSERT_HANDLER</STRONG> are not
|
||||
defined, and <code>expr</code> evaluates to <code>false</code>, an error
|
||||
message that includes <tt>#expr</tt>, <tt>msg</tt>, <tt> <a href="current_function.html">BOOST_CURRENT_FUNCTION</a></tt>, <tt>
|
||||
__FILE__</tt>, and <tt>__LINE__</tt> is sent to output stream <b>
|
||||
BOOST_ASSERT_MSG_OSTREAM</b>
|
||||
and <code>std::abort()</code> is called.</P>
|
||||
<P> <b>BOOST_ASSERT_MSG_OSTREAM</b> defines the output stream. It defaults to <code>std::cerr</code>.
|
||||
Integrated development environments (IDE's) like Microsoft Visual Studio
|
||||
may produce easier to understand output if messages go to a different
|
||||
stream, such as <code>std::cout</code>. Users may define <b>BOOST_ASSERT_MSG_OSTREAM</b> before including <STRONG><boost/assert.hpp></STRONG>
|
||||
to specify a different output stream. </P>
|
||||
<P>If the macro <STRONG>BOOST_ENABLE_ASSERT_HANDLER</STRONG> is defined when <STRONG><boost/assert.hpp></STRONG>
|
||||
is included, instead of sending a error message to an output
|
||||
stream, this expression is evaluated</P>
|
||||
<blockquote>
|
||||
<P><tt>::boost::assertion_failed_msg(#expr, msg, <a href="current_function.html">BOOST_CURRENT_FUNCTION</a>,
|
||||
__FILE__, __LINE__)</tt></P>
|
||||
</blockquote>
|
||||
<P><STRONG>assertion_failed_msg</STRONG> is declared in <STRONG><boost/assert.hpp></STRONG>
|
||||
as</P>
|
||||
<blockquote>
|
||||
<pre>namespace boost
|
||||
{
|
||||
void assertion_failed_msg(char const * expr, char const * msg, char const * function, char const * file, long line);
|
||||
}
|
||||
</pre>
|
||||
</blockquote>
|
||||
<p>but it is never defined. The user is expected to supply an appropriate
|
||||
definition.</p>
|
||||
<P>As is the case with <STRONG><cassert></STRONG>, <STRONG><boost/assert.hpp></STRONG>
|
||||
can be included multiple times in a single translation unit. <STRONG>BOOST_ASSERT_MSG</STRONG>
|
||||
will be redefined each time as specified above.</P>
|
||||
|
||||
<h2><a name="BOOST_VERIFY">BOOST_VERIFY</a></h2>
|
||||
<p><STRONG><boost/assert.hpp></STRONG> also defines the macro <STRONG>BOOST_VERIFY</STRONG>.
|
||||
It has exactly the same behavior as <STRONG>BOOST_ASSERT</STRONG>, except that
|
||||
the expression that is passed to <STRONG>BOOST_VERIFY</STRONG> is always
|
||||
@ -54,8 +107,9 @@ void assertion_failed(char const * expr, char const * function, char const * fil
|
||||
effects; it can also help suppress warnings about unused variables when the
|
||||
only use of the variable is inside an assertion.</p>
|
||||
<p><br>
|
||||
<small>Copyright <20> 2002, 2007 by Peter Dimov. Distributed under the Boost Software
|
||||
<small>Copyright <20> 2002, 2007 by Peter Dimov. Copyright <20> 2011
|
||||
by Beman Dawes. Distributed under the Boost Software
|
||||
License, Version 1.0. See accompanying file <A href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</A>
|
||||
or copy at <A href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>.</small></p>
|
||||
</body>
|
||||
</html>
|
||||
</html>
|
@ -2,6 +2,7 @@
|
||||
// assert_test.cpp - a test for boost/assert.hpp
|
||||
//
|
||||
// Copyright (c) 2002 Peter Dimov and Multi Media Ltd.
|
||||
// Copyright (2) Beman Dawes 2011
|
||||
//
|
||||
// Distributed under the Boost Software License, Version 1.0. (See
|
||||
// accompanying file LICENSE_1_0.txt or copy at
|
||||
@ -20,6 +21,11 @@ void test_default()
|
||||
BOOST_ASSERT(x);
|
||||
BOOST_ASSERT(x == 1);
|
||||
BOOST_ASSERT(&x);
|
||||
|
||||
BOOST_ASSERT_MSG(1, "msg");
|
||||
BOOST_ASSERT_MSG(x, "msg");
|
||||
BOOST_ASSERT_MSG(x == 1, "msg");
|
||||
BOOST_ASSERT_MSG(&x, "msg");
|
||||
}
|
||||
|
||||
#define BOOST_DISABLE_ASSERTS
|
||||
@ -34,13 +40,23 @@ void test_disabled()
|
||||
BOOST_ASSERT(x == 1);
|
||||
BOOST_ASSERT(&x);
|
||||
|
||||
BOOST_ASSERT_MSG(1, "msg");
|
||||
BOOST_ASSERT_MSG(x, "msg");
|
||||
BOOST_ASSERT_MSG(x == 1, "msg");
|
||||
BOOST_ASSERT_MSG(&x, "msg");
|
||||
|
||||
BOOST_ASSERT(0);
|
||||
BOOST_ASSERT(!x);
|
||||
BOOST_ASSERT(x == 0);
|
||||
|
||||
BOOST_ASSERT_MSG(0, "msg");
|
||||
BOOST_ASSERT_MSG(!x, "msg");
|
||||
BOOST_ASSERT_MSG(x == 0, "msg");
|
||||
|
||||
void * p = 0;
|
||||
|
||||
BOOST_ASSERT(p);
|
||||
BOOST_ASSERT_MSG(p, "msg");
|
||||
|
||||
// supress warnings
|
||||
p = &x;
|
||||
@ -55,6 +71,7 @@ void test_disabled()
|
||||
#include <cstdio>
|
||||
|
||||
int handler_invoked = 0;
|
||||
int msg_handler_invoked = 0;
|
||||
|
||||
void boost::assertion_failed(char const * expr, char const * function, char const * file, long line)
|
||||
{
|
||||
@ -66,11 +83,24 @@ void boost::assertion_failed(char const * expr, char const * function, char cons
|
||||
++handler_invoked;
|
||||
}
|
||||
|
||||
void boost::assertion_failed_msg(char const * expr, char const * msg, char const * function,
|
||||
char const * file, long line)
|
||||
{
|
||||
#if !defined(BOOST_NO_STDC_NAMESPACE)
|
||||
using std::printf;
|
||||
#endif
|
||||
|
||||
printf("Expression: %s Message: %s\nFunction: %s\nFile: %s\nLine: %ld\n\n",
|
||||
expr, msg, function, file, line);
|
||||
++msg_handler_invoked;
|
||||
}
|
||||
|
||||
struct X
|
||||
{
|
||||
static void f()
|
||||
{
|
||||
BOOST_ASSERT(0);
|
||||
BOOST_ASSERT_MSG(0, "msg f()");
|
||||
}
|
||||
};
|
||||
|
||||
@ -83,21 +113,35 @@ void test_handler()
|
||||
BOOST_ASSERT(x == 1);
|
||||
BOOST_ASSERT(&x);
|
||||
|
||||
BOOST_ASSERT_MSG(1, "msg2");
|
||||
BOOST_ASSERT_MSG(x, "msg3");
|
||||
BOOST_ASSERT_MSG(x == 1, "msg4");
|
||||
BOOST_ASSERT_MSG(&x, "msg5");
|
||||
|
||||
BOOST_ASSERT(0);
|
||||
BOOST_ASSERT(!x);
|
||||
BOOST_ASSERT(x == 0);
|
||||
|
||||
BOOST_ASSERT_MSG(0,"msg 0");
|
||||
BOOST_ASSERT_MSG(!x, "msg !x");
|
||||
BOOST_ASSERT_MSG(x == 0, "msg x == 0");
|
||||
|
||||
void * p = 0;
|
||||
|
||||
BOOST_ASSERT(p);
|
||||
BOOST_ASSERT_MSG(p, "msg p");
|
||||
|
||||
X::f();
|
||||
|
||||
BOOST_ASSERT(handler_invoked == 5);
|
||||
BOOST_TEST(handler_invoked == 5);
|
||||
|
||||
BOOST_ASSERT_MSG(msg_handler_invoked == 5, "msg_handler_invoked count is wrong");
|
||||
BOOST_TEST(msg_handler_invoked == 5);
|
||||
}
|
||||
|
||||
#undef BOOST_ENABLE_ASSERT_HANDLER
|
||||
#undef BOOST_ENABLE_ASSERT_MSG_HANDLER
|
||||
|
||||
int main()
|
||||
{
|
||||
|
68
doc/Jamfile.v2
Normal file
68
doc/Jamfile.v2
Normal file
@ -0,0 +1,68 @@
|
||||
|
||||
# Copyright John Maddock 2005. Use, modification, and distribution are
|
||||
# subject to 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)
|
||||
|
||||
project : requirements
|
||||
# Path for links to Boost:
|
||||
<xsl:param>boost.root=../../../..
|
||||
|
||||
# Some general style settings:
|
||||
<xsl:param>table.footnote.number.format=1
|
||||
<xsl:param>footnote.number.format=1
|
||||
|
||||
# HTML options first:
|
||||
# Use graphics not text for navigation:
|
||||
<xsl:param>navig.graphics=1
|
||||
# PDF Options:
|
||||
# TOC Generation: this is needed for FOP-0.9 and later:
|
||||
<xsl:param>fop1.extensions=0
|
||||
<xsl:param>xep.extensions=1
|
||||
# TOC generation: this is needed for FOP 0.2, but must not be set to zero for FOP-0.9!
|
||||
<xsl:param>fop.extensions=0
|
||||
# No indent on body text:
|
||||
<xsl:param>body.start.indent=0pt
|
||||
# Margin size:
|
||||
<xsl:param>page.margin.inner=0.5in
|
||||
# Margin size:
|
||||
<xsl:param>page.margin.outer=0.5in
|
||||
# Paper type = A4
|
||||
<xsl:param>paper.type=A4
|
||||
# Yes, we want graphics for admonishments:
|
||||
<xsl:param>admon.graphics=1
|
||||
# Set this one for PDF generation *only*:
|
||||
# default pnd graphics are awful in PDF form,
|
||||
# better use SVG's instead:
|
||||
<format>pdf:<xsl:param>admon.graphics.extension=".svg"
|
||||
<format>pdf:<xsl:param>admon.graphics.path=$(boost-images)/
|
||||
<format>pdf:<xsl:param>boost.url.prefix=http://www.boost.org/doc/libs/release/libs/utility/doc/html
|
||||
;
|
||||
|
||||
using quickbook ;
|
||||
|
||||
path-constant boost-images : ../../../doc/src/images ;
|
||||
|
||||
xml declval : declval.qbk ;
|
||||
boostbook standalone
|
||||
:
|
||||
declval
|
||||
:
|
||||
# File name of HTML output:
|
||||
<xsl:param>root.filename=declval
|
||||
# How far down we chunk nested sections, basically all of them:
|
||||
<xsl:param>chunk.section.depth=0
|
||||
# Don't put the first section on the same page as the TOC:
|
||||
<xsl:param>chunk.first.sections=0
|
||||
# How far down sections get TOC's
|
||||
<xsl:param>toc.section.depth=1
|
||||
# Max depth in each TOC:
|
||||
<xsl:param>toc.max.depth=1
|
||||
# How far down we go with TOC's
|
||||
<xsl:param>generate.section.toc.level=1
|
||||
|
||||
;
|
||||
|
||||
|
||||
|
||||
|
||||
|
104
doc/declval.qbk
Normal file
104
doc/declval.qbk
Normal file
@ -0,0 +1,104 @@
|
||||
[/
|
||||
/ Copyright (c) 2008 Howard Hinnant
|
||||
/ Copyright (c) 2008 Beman Dawes
|
||||
/ Copyright (c) 2009-20010 Vicente J. Botet Escriba
|
||||
/
|
||||
/ 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)
|
||||
/]
|
||||
|
||||
[article Declval
|
||||
[quickbook 1.5]
|
||||
[authors [Hinnant, Howard]]
|
||||
[authors [Dawes, Beman]]
|
||||
[authors [Botet Escriba, Vicente J.]]
|
||||
[copyright 2008 Howard Hinnant]
|
||||
[copyright 2008 Beman Dawes]
|
||||
[copyright 2009-2010 Vicente J. Botet Escriba]
|
||||
[license
|
||||
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])
|
||||
]
|
||||
]
|
||||
|
||||
[/===============]
|
||||
[section Overview]
|
||||
[/===============]
|
||||
|
||||
The motivation for `declval` was introduced in [@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2958.html#Value N2958:
|
||||
Moving Swap Forward]. Here follows a rewording of this chapter.
|
||||
|
||||
With the provision of decltype, late-specified return types, and default template-arguments for function templates a
|
||||
new generation of SFINAE patterns will emerge to at least partially compensate the lack of concepts on the C++0x timescale.
|
||||
Using this technique, it is sometimes necessary to obtain an object of a known type in a non-using context, e.g. given the declaration
|
||||
|
||||
template<class T>
|
||||
T&& declval(); // not used
|
||||
|
||||
as part of the function template declaration
|
||||
|
||||
template<class To, class From>
|
||||
decltype(static_cast<To>(declval<From>())) convert(From&&);
|
||||
|
||||
or as part of a class template definition
|
||||
|
||||
template<class> class result_of;
|
||||
|
||||
template<class Fn, class... ArgTypes>
|
||||
struct result_of<Fn(ArgTypes...)>
|
||||
{
|
||||
typedef decltype(declval<Fn>()(declval<ArgTypes>()...)) type;
|
||||
};
|
||||
|
||||
The role of the function template declval() is a transformation of a type T into a value without using or evaluating this function.
|
||||
The name is supposed to direct the reader's attention to the fact that the expression `declval<T>()` is an lvalue if and only if
|
||||
T is an lvalue-reference, otherwise an rvalue. To extend the domain of this function we can do a bit better by changing its declaration to
|
||||
|
||||
template<class T>
|
||||
typename std::add_rvalue_reference<T>::type declval(); // not used
|
||||
|
||||
which ensures that we can also use cv void as template parameter. The careful reader might have noticed that `declval()`
|
||||
already exists under the name create() as part of the definition of the semantics of the type trait is_convertible in the C==0x standard.
|
||||
|
||||
The provision of a new library component that allows the production of values in unevaluated expressions is considered as
|
||||
important to realize constrained templates in C++0x where concepts are not available.
|
||||
This extremely light-weight function is expected to be part of the daily tool-box of the C++0x programmer.
|
||||
|
||||
[endsect]
|
||||
|
||||
|
||||
[/=================]
|
||||
[section:reference Reference ]
|
||||
[/=================]
|
||||
|
||||
`#include <boost/utility/declval.hpp>`
|
||||
|
||||
namespace boost {
|
||||
|
||||
template <typename T>
|
||||
typename add_rvalue_reference<T>::type declval(); //noexcept; // as unevaluated operand
|
||||
|
||||
} // namespace boost
|
||||
|
||||
|
||||
The library provides the function template declval to simplify the definition of expressions which occur as unevaluated operands.
|
||||
|
||||
template <typename T>
|
||||
typename add_rvalue_reference<T>::type declval();
|
||||
|
||||
[*Remarks:] If this function is used, the program is ill-formed.
|
||||
|
||||
[*Remarks:] The template parameter T of declval may be an incomplete type.
|
||||
|
||||
[*Example:]
|
||||
|
||||
template <class To, class From>
|
||||
decltype(static_cast<To>(declval<From>())) convert(From&&);
|
||||
|
||||
Declares a function template convert which only participats in overloading if the type From can be explicitly converted to type To.
|
||||
|
||||
[endsect]
|
||||
|
||||
|
||||
|
163
doc/html/declval.html
Normal file
163
doc/html/declval.html
Normal file
@ -0,0 +1,163 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Declval</title>
|
||||
<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.74.0">
|
||||
<link rel="home" href="declval.html" title="Declval">
|
||||
</head>
|
||||
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
||||
<table cellpadding="2" width="100%"><tr>
|
||||
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
|
||||
<td align="center"><a href="../../../../index.html">Home</a></td>
|
||||
<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
|
||||
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
|
||||
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
|
||||
<td align="center"><a href="../../../../more/index.htm">More</a></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav"></div>
|
||||
<div class="article" lang="en">
|
||||
<div class="titlepage">
|
||||
<div>
|
||||
<div><h2 class="title">
|
||||
<a name="declval"></a>Declval</h2></div>
|
||||
<div><div class="authorgroup">
|
||||
<div class="author"><h3 class="author">
|
||||
<span class="firstname">Howard</span> <span class="surname">Hinnant</span>
|
||||
</h3></div>
|
||||
<div class="author"><h3 class="author">
|
||||
<span class="firstname">Beman</span> <span class="surname">Dawes</span>
|
||||
</h3></div>
|
||||
<div class="author"><h3 class="author">
|
||||
<span class="firstname">Vicente J.</span> <span class="surname">Botet Escriba</span>
|
||||
</h3></div>
|
||||
</div></div>
|
||||
<div><p class="copyright">Copyright © 2008 Howard Hinnant</p></div>
|
||||
<div><p class="copyright">Copyright © 2008 Beman Dawes</p></div>
|
||||
<div><p class="copyright">Copyright © 2009 -2010 Vicente J. Botet Escriba</p></div>
|
||||
<div><div class="legalnotice">
|
||||
<a name="id879409"></a><p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
</div></div>
|
||||
</div>
|
||||
<hr>
|
||||
</div>
|
||||
<div class="toc">
|
||||
<p><b>Table of Contents</b></p>
|
||||
<dl>
|
||||
<dt><span class="section"><a href="declval.html#declval.overview">Overview</a></span></dt>
|
||||
<dt><span class="section"><a href="declval.html#declval.reference"> Reference </a></span></dt>
|
||||
</dl>
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="declval.overview"></a><a class="link" href="declval.html#declval.overview" title="Overview">Overview</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
The motivation for <code class="computeroutput"><span class="identifier">declval</span></code>
|
||||
was introduced in <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2958.html#Value" target="_top">N2958:
|
||||
Moving Swap Forward</a>. Here follows a rewording of this chapter.
|
||||
</p>
|
||||
<p>
|
||||
With the provision of decltype, late-specified return types, and default template-arguments
|
||||
for function templates a new generation of SFINAE patterns will emerge to at
|
||||
least partially compensate the lack of concepts on the C++0x timescale. Using
|
||||
this technique, it is sometimes necessary to obtain an object of a known type
|
||||
in a non-using context, e.g. given the declaration
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span>
|
||||
<span class="identifier">T</span><span class="special">&&</span> <span class="identifier">declval</span><span class="special">();</span> <span class="comment">// not used
|
||||
</span></pre>
|
||||
<p>
|
||||
as part of the function template declaration
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">To</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">From</span><span class="special">></span>
|
||||
<span class="identifier">decltype</span><span class="special">(</span><span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">declval</span><span class="special"><</span><span class="identifier">From</span><span class="special">>()))</span> <span class="identifier">convert</span><span class="special">(</span><span class="identifier">From</span><span class="special">&&);</span>
|
||||
</pre>
|
||||
<p>
|
||||
or as part of a class template definition
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">></span> <span class="keyword">class</span> <span class="identifier">result_of</span><span class="special">;</span>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> <span class="identifier">ArgTypes</span><span class="special">></span>
|
||||
<span class="keyword">struct</span> <span class="identifier">result_of</span><span class="special"><</span><span class="identifier">Fn</span><span class="special">(</span><span class="identifier">ArgTypes</span><span class="special">...)></span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">typedef</span> <span class="identifier">decltype</span><span class="special">(</span><span class="identifier">declval</span><span class="special"><</span><span class="identifier">Fn</span><span class="special">>()(</span><span class="identifier">declval</span><span class="special"><</span><span class="identifier">ArgTypes</span><span class="special">>()...))</span> <span class="identifier">type</span><span class="special">;</span>
|
||||
<span class="special">};</span>
|
||||
</pre>
|
||||
<p>
|
||||
The role of the function template declval() is a transformation of a type T
|
||||
into a value without using or evaluating this function. The name is supposed
|
||||
to direct the reader's attention to the fact that the expression <code class="computeroutput"><span class="identifier">declval</span><span class="special"><</span><span class="identifier">T</span><span class="special">>()</span></code> is
|
||||
an lvalue if and only if T is an lvalue-reference, otherwise an rvalue. To
|
||||
extend the domain of this function we can do a bit better by changing its declaration
|
||||
to
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span>
|
||||
<span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">add_rvalue_reference</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">declval</span><span class="special">();</span> <span class="comment">// not used
|
||||
</span></pre>
|
||||
<p>
|
||||
which ensures that we can also use cv void as template parameter. The careful
|
||||
reader might have noticed that <code class="computeroutput"><span class="identifier">declval</span><span class="special">()</span></code> already exists under the name create() as
|
||||
part of the definition of the semantics of the type trait is_convertible in
|
||||
the C==0x standard.
|
||||
</p>
|
||||
<p>
|
||||
The provision of a new library component that allows the production of values
|
||||
in unevaluated expressions is considered as important to realize constrained
|
||||
templates in C++0x where concepts are not available. This extremely light-weight
|
||||
function is expected to be part of the daily tool-box of the C++0x programmer.
|
||||
</p>
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="declval.reference"></a><a class="link" href="declval.html#declval.reference" title="Reference"> Reference </a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">utility</span><span class="special">/</span><span class="identifier">declval</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code>
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
|
||||
|
||||
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span>
|
||||
<span class="keyword">typename</span> <span class="identifier">add_rvalue_reference</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">declval</span><span class="special">();</span> <span class="comment">//noexcept; // as unevaluated operand
|
||||
</span>
|
||||
<span class="special">}</span> <span class="comment">// namespace boost
|
||||
</span></pre>
|
||||
<p>
|
||||
The library provides the function template declval to simplify the definition
|
||||
of expressions which occur as unevaluated operands.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span>
|
||||
<span class="keyword">typename</span> <span class="identifier">add_rvalue_reference</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">declval</span><span class="special">();</span>
|
||||
</pre>
|
||||
<p>
|
||||
<span class="bold"><strong>Remarks:</strong></span> If this function is used, the program
|
||||
is ill-formed.
|
||||
</p>
|
||||
<p>
|
||||
<span class="bold"><strong>Remarks:</strong></span> The template parameter T of declval
|
||||
may be an incomplete type.
|
||||
</p>
|
||||
<p>
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">To</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">From</span><span class="special">></span>
|
||||
<span class="identifier">decltype</span><span class="special">(</span><span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">declval</span><span class="special"><</span><span class="identifier">From</span><span class="special">>()))</span> <span class="identifier">convert</span><span class="special">(</span><span class="identifier">From</span><span class="special">&&);</span>
|
||||
</pre>
|
||||
<p>
|
||||
Declares a function template convert which only participats in overloading
|
||||
if the type From can be explicitly converted to type To.
|
||||
</p>
|
||||
</div>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"><p><small>Last revised: September 16, 2010 at 16:19:10 GMT</small></p></td>
|
||||
<td align="right"><div class="copyright-footer"></div></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav"></div>
|
||||
</body>
|
||||
</html>
|
@ -1,8 +1,11 @@
|
||||
//
|
||||
// boost/assert.hpp - BOOST_ASSERT(expr)
|
||||
// BOOST_ASSERT_MSG(expr, msg)
|
||||
// BOOST_VERIFY(expr)
|
||||
//
|
||||
// Copyright (c) 2001, 2002 Peter Dimov and Multi Media Ltd.
|
||||
// Copyright (c) 2007 Peter Dimov
|
||||
// Copyright (c) Beman Dawes 2011
|
||||
//
|
||||
// Distributed under the Boost Software License, Version 1.0. (See
|
||||
// accompanying file LICENSE_1_0.txt or copy at
|
||||
@ -13,6 +16,16 @@
|
||||
// See http://www.boost.org/libs/utility/assert.html for documentation.
|
||||
//
|
||||
|
||||
//
|
||||
// Stop inspect complaining about use of 'assert':
|
||||
//
|
||||
// boostinspect:naassert_macro
|
||||
//
|
||||
|
||||
//--------------------------------------------------------------------------------------//
|
||||
// BOOST_ASSERT //
|
||||
//--------------------------------------------------------------------------------------//
|
||||
|
||||
#undef BOOST_ASSERT
|
||||
|
||||
#if defined(BOOST_DISABLE_ASSERTS)
|
||||
@ -25,18 +38,86 @@
|
||||
|
||||
namespace boost
|
||||
{
|
||||
|
||||
void assertion_failed(char const * expr, char const * function, char const * file, long line); // user defined
|
||||
|
||||
void assertion_failed(char const * expr,
|
||||
char const * function, char const * file, long line); // user defined
|
||||
} // namespace boost
|
||||
|
||||
#define BOOST_ASSERT(expr) ((expr)? ((void)0): ::boost::assertion_failed(#expr, BOOST_CURRENT_FUNCTION, __FILE__, __LINE__))
|
||||
#define BOOST_ASSERT(expr) ((expr) \
|
||||
? ((void)0) \
|
||||
: ::boost::assertion_failed(#expr, BOOST_CURRENT_FUNCTION, __FILE__, __LINE__))
|
||||
|
||||
#else
|
||||
# include <assert.h> // .h to support old libraries w/o <cassert> - effect is the same
|
||||
# define BOOST_ASSERT(expr) assert(expr)
|
||||
#endif
|
||||
|
||||
//--------------------------------------------------------------------------------------//
|
||||
// BOOST_ASSERT_MSG //
|
||||
//--------------------------------------------------------------------------------------//
|
||||
|
||||
# undef BOOST_ASSERT_MSG
|
||||
|
||||
#if defined(BOOST_DISABLE_ASSERTS) || defined(NDEBUG)
|
||||
|
||||
#define BOOST_ASSERT_MSG(expr, msg) ((void)0)
|
||||
|
||||
#elif defined(BOOST_ENABLE_ASSERT_HANDLER)
|
||||
|
||||
#include <boost/current_function.hpp>
|
||||
|
||||
namespace boost
|
||||
{
|
||||
void assertion_failed_msg(char const * expr, char const * msg,
|
||||
char const * function, char const * file, long line); // user defined
|
||||
} // namespace boost
|
||||
|
||||
#define BOOST_ASSERT_MSG(expr, msg) ((expr) \
|
||||
? ((void)0) \
|
||||
: ::boost::assertion_failed_msg(#expr, msg, BOOST_CURRENT_FUNCTION, __FILE__, __LINE__))
|
||||
|
||||
#else
|
||||
#ifndef BOOST_ASSERT_HPP
|
||||
#define BOOST_ASSERT_HPP
|
||||
#include <cstdlib>
|
||||
#include <iostream>
|
||||
#include <boost/current_function.hpp>
|
||||
|
||||
// IDE's like Visual Studio perform better if output goes to std::cout or
|
||||
// some other stream, so allow user to configure output stream:
|
||||
#ifndef BOOST_ASSERT_MSG_OSTREAM
|
||||
# define BOOST_ASSERT_MSG_OSTREAM std::cerr
|
||||
#endif
|
||||
|
||||
namespace boost
|
||||
{
|
||||
namespace assertion
|
||||
{
|
||||
namespace detail
|
||||
{
|
||||
inline void assertion_failed_msg(char const * expr, char const * msg, char const * function,
|
||||
char const * file, long line)
|
||||
{
|
||||
BOOST_ASSERT_MSG_OSTREAM
|
||||
<< "***** Internal Program Error - assertion (" << expr << ") failed in "
|
||||
<< function << ":\n"
|
||||
<< file << '(' << line << "): " << msg << std::endl;
|
||||
std::abort();
|
||||
}
|
||||
} // detail
|
||||
} // assertion
|
||||
} // detail
|
||||
#endif
|
||||
|
||||
#define BOOST_ASSERT_MSG(expr, msg) ((expr) \
|
||||
? ((void)0) \
|
||||
: ::boost::assertion::detail::assertion_failed_msg(#expr, msg, \
|
||||
BOOST_CURRENT_FUNCTION, __FILE__, __LINE__))
|
||||
#endif
|
||||
|
||||
//--------------------------------------------------------------------------------------//
|
||||
// BOOST_VERIFY //
|
||||
//--------------------------------------------------------------------------------------//
|
||||
|
||||
#undef BOOST_VERIFY
|
||||
|
||||
#if defined(BOOST_DISABLE_ASSERTS) || ( !defined(BOOST_ENABLE_ASSERT_HANDLER) && defined(NDEBUG) )
|
||||
|
@ -8,6 +8,8 @@
|
||||
// See http://www.boost.org/libs/utility/operators.htm for documentation.
|
||||
|
||||
// Revision History
|
||||
// 16 Dec 10 Limit warning suppression for 4284 to older versions of VC++
|
||||
// (Matthew Bradbury, fixes #4432)
|
||||
// 07 Aug 08 Added "euclidean" spelling. (Daniel Frey)
|
||||
// 03 Apr 08 Make sure "convertible to bool" is sufficient
|
||||
// for T::operator<, etc. (Daniel Frey)
|
||||
@ -88,7 +90,7 @@
|
||||
# pragma set woff 1234
|
||||
#endif
|
||||
|
||||
#if defined(BOOST_MSVC)
|
||||
#if BOOST_WORKAROUND(BOOST_MSVC, < 1600)
|
||||
# pragma warning( disable : 4284 ) // complaint about return type of
|
||||
#endif // operator-> not begin a UDT
|
||||
|
||||
|
@ -4,7 +4,7 @@
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
// See http://www.boost.org/libs/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// fernando_cacciola@hotmail.com
|
||||
|
44
include/boost/utility/declval.hpp
Normal file
44
include/boost/utility/declval.hpp
Normal file
@ -0,0 +1,44 @@
|
||||
// common_type.hpp ---------------------------------------------------------//
|
||||
|
||||
// Copyright 2010 Vicente J. Botet Escriba
|
||||
|
||||
// Distributed under the Boost Software License, Version 1.0.
|
||||
// See http://www.boost.org/LICENSE_1_0.txt
|
||||
|
||||
#ifndef BOOST_TYPE_TRAITS_EXT_DECLVAL__HPP
|
||||
#define BOOST_TYPE_TRAITS_EXT_DECLVAL__HPP
|
||||
|
||||
#include <boost/config.hpp>
|
||||
|
||||
//----------------------------------------------------------------------------//
|
||||
|
||||
#include <boost/type_traits/add_rvalue_reference.hpp>
|
||||
|
||||
//----------------------------------------------------------------------------//
|
||||
// //
|
||||
// C++03 implementation of //
|
||||
// Written by Vicente J. Botet Escriba //
|
||||
//~ 20.3.4 Function template declval [declval]
|
||||
//~ 1 The library provides the function template declval to simplify the definition of expressions which occur as
|
||||
//~ unevaluated operands.
|
||||
//~ 2 Remarks: If this function is used, the program is ill-formed.
|
||||
//~ 3 Remarks: The template parameter T of declval may be an incomplete type.
|
||||
//~ [ Example:
|
||||
|
||||
//~ template <class To, class From>
|
||||
//~ decltype(static_cast<To>(declval<From>())) convert(From&&);
|
||||
|
||||
//~ declares a function template convert which only participats in overloading if the type From can be
|
||||
//~ explicitly converted to type To. For another example see class template common_type (20.7.6.6). <20>end
|
||||
//~ example ]
|
||||
// //
|
||||
//----------------------------------------------------------------------------//
|
||||
|
||||
namespace boost {
|
||||
|
||||
template <typename T>
|
||||
typename add_rvalue_reference<T>::type declval(); //noexcept; // as unevaluated operand
|
||||
|
||||
} // namespace boost
|
||||
|
||||
#endif // BOOST_TYPE_TRAITS_EXT_DECLVAL__HPP
|
@ -5,7 +5,7 @@
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
// See http://www.boost.org/libs/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// fernando_cacciola@hotmail.com
|
||||
|
@ -5,7 +5,7 @@
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
// See http://www.boost.org/libs/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// fernando_cacciola@hotmail.com
|
||||
|
@ -35,10 +35,7 @@ struct tr1_result_of<F(BOOST_RESULT_OF_ARGS)>
|
||||
|
||||
#if !defined(BOOST_NO_DECLTYPE) && defined(BOOST_RESULT_OF_USE_DECLTYPE)
|
||||
|
||||
// As of N2588, C++0x result_of only supports function call
|
||||
// expressions of the form f(x). This precludes support for member
|
||||
// function pointers, which are invoked with expressions of the form
|
||||
// o->*f(x). This implementation supports both.
|
||||
// Uses declval following N3225 20.7.7.6 when F is not a pointer.
|
||||
template<typename F BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
|
||||
BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
|
||||
struct result_of<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
|
||||
@ -56,18 +53,15 @@ struct result_of<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
|
||||
|
||||
namespace detail {
|
||||
|
||||
# define BOOST_RESULT_OF_STATIC_MEMBERS(z, n, _) \
|
||||
static T ## n t ## n; \
|
||||
/**/
|
||||
|
||||
template<typename F BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
|
||||
BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
|
||||
class cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
|
||||
struct cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
|
||||
{
|
||||
static F f;
|
||||
BOOST_PP_REPEAT(BOOST_PP_ITERATION(), BOOST_RESULT_OF_STATIC_MEMBERS, _)
|
||||
public:
|
||||
typedef decltype(f(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),t))) type;
|
||||
typedef decltype(
|
||||
boost::declval<F>()(
|
||||
BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), declval<T, >() BOOST_PP_INTERCEPT)
|
||||
)
|
||||
) type;
|
||||
};
|
||||
|
||||
} // namespace detail
|
||||
|
@ -5,7 +5,7 @@
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
// See http://www.boost.org/libs/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// fernando_cacciola@hotmail.com
|
||||
|
@ -13,7 +13,9 @@
|
||||
#include <boost/preprocessor/iteration/iterate.hpp>
|
||||
#include <boost/preprocessor/punctuation/comma_if.hpp>
|
||||
#include <boost/preprocessor/repetition/enum_params.hpp>
|
||||
#include <boost/preprocessor/repetition/enum_binary_params.hpp>
|
||||
#include <boost/preprocessor/repetition/enum_shifted_params.hpp>
|
||||
#include <boost/preprocessor/facilities/intercept.hpp>
|
||||
#include <boost/detail/workaround.hpp>
|
||||
#include <boost/mpl/has_xxx.hpp>
|
||||
#include <boost/mpl/if.hpp>
|
||||
@ -22,6 +24,7 @@
|
||||
#include <boost/type_traits/is_pointer.hpp>
|
||||
#include <boost/type_traits/is_member_function_pointer.hpp>
|
||||
#include <boost/type_traits/remove_cv.hpp>
|
||||
#include <boost/utility/declval.hpp>
|
||||
|
||||
#ifndef BOOST_RESULT_OF_NUM_ARGS
|
||||
# define BOOST_RESULT_OF_NUM_ARGS 10
|
||||
|
@ -5,7 +5,7 @@
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
// See http://www.boost.org/libs/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// fernando_cacciola@hotmail.com
|
||||
|
12
index.html
12
index.html
@ -14,20 +14,28 @@
|
||||
<p>But that doesn't mean there isn't useful stuff here. Take a look:</p>
|
||||
<blockquote>
|
||||
<p>
|
||||
<a href="utility.htm#addressof">addressof</a><br>
|
||||
<a href="assert.html">assert</a><br>
|
||||
<a href="base_from_member.html">base_from_member</a><br>
|
||||
<a href="utility.htm#BOOST_BINARY">BOOST_BINARY</a><br>
|
||||
<a href="call_traits.htm">call_traits</a><br>
|
||||
<a href="checked_delete.html">checked_delete</a><br>
|
||||
<a href="compressed_pair.htm">compressed_pair</a><br>
|
||||
<a href="current_function.html">current_function</a><br>
|
||||
<a href="enable_if.html">enable_if</a><br>
|
||||
<a href="doc/html/declval.html">declval</a><br>
|
||||
<a href="enable_if.html">enable_if</a><br>
|
||||
<a href="in_place_factories.html">in_place_factory</a><br>
|
||||
<a href="iterator_adaptors.htm">iterator_adaptors</a><br>
|
||||
<a href="generator_iterator.htm">generator iterator adaptors</a><br>
|
||||
<a href="utility.htm#functions_next_prior">next/prior</a><br>
|
||||
<a href="utility.htm#Class_noncopyable">noncopyable</a><br>
|
||||
<a href="operators.htm">operators</a><br>
|
||||
<a href="utility.htm#result_of">result_of</a><br>
|
||||
<a href="swap.html">swap</a><br>
|
||||
<a href="throw_exception.html">throw_exception</a><br>
|
||||
<a href="utility.htm">utility</a><br>
|
||||
<a href="value_init.htm">value_init</a></p>
|
||||
<a href="value_init.htm">value_init</a>
|
||||
</p>
|
||||
</blockquote>
|
||||
<hr>
|
||||
<p>© Copyright Beman Dawes, 2001</p>
|
||||
|
@ -32,6 +32,7 @@ test-suite utility
|
||||
[ compile result_of_test.cpp ]
|
||||
[ run ../shared_iterator_test.cpp ]
|
||||
[ run ../value_init_test.cpp ]
|
||||
[ run ../value_init_workaround_test.cpp ]
|
||||
[ run ../initialized_test.cpp ]
|
||||
[ compile-fail ../value_init_test_fail1.cpp ]
|
||||
[ compile-fail ../value_init_test_fail2.cpp ]
|
||||
|
0
test/next_prior_test.cpp
Executable file → Normal file
0
test/next_prior_test.cpp
Executable file → Normal file
@ -98,6 +98,11 @@ struct no_result_type_or_result_of
|
||||
unsigned int operator()();
|
||||
unsigned short operator()() volatile;
|
||||
const unsigned short operator()() const volatile;
|
||||
#if !defined(BOOST_NO_RVALUE_REFERENCES)
|
||||
short operator()(int&&);
|
||||
int operator()(int&);
|
||||
long operator()(int const&);
|
||||
#endif
|
||||
};
|
||||
|
||||
template<typename T>
|
||||
@ -108,6 +113,11 @@ struct no_result_type_or_result_of_template
|
||||
unsigned int operator()();
|
||||
unsigned short operator()() volatile;
|
||||
const unsigned short operator()() const volatile;
|
||||
#if !defined(BOOST_NO_RVALUE_REFERENCES)
|
||||
short operator()(int&&);
|
||||
int operator()(int&);
|
||||
long operator()(int const&);
|
||||
#endif
|
||||
};
|
||||
|
||||
struct X {};
|
||||
@ -232,6 +242,14 @@ int main()
|
||||
BOOST_STATIC_ASSERT((is_same<result_of<const no_result_type_or_result_of_template<void>(double)>::type, short>::value));
|
||||
BOOST_STATIC_ASSERT((is_same<result_of<volatile no_result_type_or_result_of_template<void>(void)>::type, unsigned short>::value));
|
||||
BOOST_STATIC_ASSERT((is_same<result_of<const volatile no_result_type_or_result_of_template<void>(void)>::type, const unsigned short>::value));
|
||||
#if !defined(BOOST_NO_RVALUE_REFERENCES)
|
||||
BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of(int&&)>::type, short>::value));
|
||||
BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of(int&)>::type, int>::value));
|
||||
BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of(int const&)>::type, long>::value));
|
||||
BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of_template<void>(int&&)>::type, short>::value));
|
||||
BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of_template<void>(int&)>::type, int>::value));
|
||||
BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of_template<void>(int const&)>::type, long>::value));
|
||||
#endif
|
||||
#endif
|
||||
|
||||
return 0;
|
||||
|
98
utility.htm
98
utility.htm
@ -151,37 +151,95 @@ void f() {
|
||||
<code>result_of<F(T1, T2, ...,
|
||||
T<em>N</em>)>::type</code> defines the result type
|
||||
of the expression <code>f(t1, t2,
|
||||
...,t<em>N</em>)</code>. The implementation permits
|
||||
...,t<em>N</em>)</code>. This implementation permits
|
||||
the type <code>F</code> to be a function pointer,
|
||||
function reference, member function pointer, or class
|
||||
type.</p> <p>If your compiler does not support
|
||||
<code>decltype</code>, then when <code>F</code> is a
|
||||
class type with a member type <code>result_type</code>,
|
||||
type. By default, <em>N</em> may be any value between 0 and
|
||||
10. To change the upper limit, define the macro
|
||||
<code>BOOST_RESULT_OF_NUM_ARGS</code> to the maximum
|
||||
value for <em>N</em>. Class template <code>result_of</code>
|
||||
resides in the header <code><<a
|
||||
href="../../boost/utility/result_of.hpp">boost/utility/result_of.hpp</a>></code>.</p>
|
||||
|
||||
<p>If your compiler supports <code>decltype</code>,
|
||||
then you can enable automatic result type deduction by
|
||||
defining the macro <code>BOOST_RESULT_OF_USE_DECLTYPE</code>,
|
||||
as in the following example.</p>
|
||||
|
||||
<blockquote>
|
||||
<pre>#define BOOST_RESULT_OF_USE_DECLTYPE
|
||||
#include <boost/utility/result_of.hpp>
|
||||
|
||||
struct functor {
|
||||
template<class T>
|
||||
T operator()(T x)
|
||||
{
|
||||
return x;
|
||||
}
|
||||
};
|
||||
|
||||
typedef boost::result_of<
|
||||
functor(int)
|
||||
>::type type;</pre>
|
||||
</blockquote>
|
||||
|
||||
<p>If <code>decltype</code> is not enabled,
|
||||
then automatic result type deduction of function
|
||||
objects is not possible. Instead, <code>result_of</code>
|
||||
uses the following protocol to allow the programmer to
|
||||
specify a type. When <code>F</code> is a class type with a
|
||||
member type <code>result_type</code>,
|
||||
<code>result_of<F(T1, T2, ...,
|
||||
T<em>N</em>)></code> is
|
||||
<code>F::result_type</code>. When <code>F</code>
|
||||
does not contain <code>result_type</code>,
|
||||
<code>F::result_type</code>. When <code>F</code> does
|
||||
not contain <code>result_type</code>,
|
||||
<code>result_of<F(T1, T2, ...,
|
||||
T<em>N</em>)></code> is <code>F::result<F(T1,
|
||||
T2, ..., T<em>N</em>)>::type</code> when
|
||||
<code><em>N</em> > 0</code> or <code>void</code>
|
||||
when <code><em>N</em> = 0</code>. For additional
|
||||
information about <code>result_of</code>, see the
|
||||
C++ Library Technical Report, <a
|
||||
href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf">N1836</a>,
|
||||
or, for motivation and design rationale, the <code>result_of</code> <a
|
||||
href="http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1454.html">proposal</a>.</p>
|
||||
when <code><em>N</em> = 0</code>. Note that it is the
|
||||
responsibility of the programmer to ensure that
|
||||
function objects accurately advertise their result
|
||||
type via this protocol, as in the following
|
||||
example.</p>
|
||||
|
||||
<p>Class template <code>result_of</code> resides in
|
||||
the header <code><<a
|
||||
href="../../boost/utility/result_of.hpp">boost/utility/result_of.hpp</a>></code>. By
|
||||
default, <em>N</em> may be any value between 0 and
|
||||
10. To change the upper limit, define the macro
|
||||
<code>BOOST_RESULT_OF_NUM_ARGS</code> to the maximum
|
||||
value for <em>N</em>.</p>
|
||||
<blockquote>
|
||||
<pre>struct functor {
|
||||
template<class> struct result;
|
||||
|
||||
template<class F, class T>
|
||||
struct result<F(T)> {
|
||||
typedef T type;
|
||||
};
|
||||
|
||||
template<class T>
|
||||
T operator()(T x)
|
||||
{
|
||||
return x;
|
||||
}
|
||||
};
|
||||
|
||||
typedef boost::result_of<
|
||||
functor(int)
|
||||
>::type type;</pre>
|
||||
</blockquote>
|
||||
|
||||
<a name="BOOST_NO_RESULT_OF"></a>
|
||||
<p>This implementation of <code>result_of</code> requires class template partial specialization, the ability to parse function types properly, and support for SFINAE. If <code>result_of</code> is not supported by your compiler, including the header <code>boost/utility/result_of.hpp</code> will define the macro <code>BOOST_NO_RESULT_OF</code>. Contributed by Doug Gregor.</p>
|
||||
<p>This implementation of <code>result_of</code>
|
||||
requires class template partial specialization, the
|
||||
ability to parse function types properly, and support
|
||||
for SFINAE. If <code>result_of</code> is not supported
|
||||
by your compiler, including the header
|
||||
<code>boost/utility/result_of.hpp</code> will
|
||||
define the macro <code>BOOST_NO_RESULT_OF</code>.</p>
|
||||
|
||||
<p>For additional information
|
||||
about <code>result_of</code>, see the C++ Library
|
||||
Technical Report,
|
||||
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf">N1836</a>,
|
||||
or, for motivation and design rationale,
|
||||
the <code>result_of</code> <a href="http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1454.html">proposal</a>.</p>
|
||||
Contributed by Doug Gregor.</p>
|
||||
|
||||
<h2>Class templates for the Base-from-Member Idiom</h2>
|
||||
<p>See <a href="base_from_member.html">separate documentation</a>.</p>
|
||||
|
144
value_init_workaround_test.cpp
Normal file
144
value_init_workaround_test.cpp
Normal file
@ -0,0 +1,144 @@
|
||||
// Copyright 2010, Niels Dekker.
|
||||
//
|
||||
// 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)
|
||||
//
|
||||
// Test program for the boost::value_initialized<T> workaround.
|
||||
//
|
||||
// 17 June 2010 (Created) Niels Dekker
|
||||
|
||||
// Switch the workaround off, before inluding "value_init.hpp".
|
||||
#define BOOST_DETAIL_VALUE_INIT_WORKAROUND 0
|
||||
#include <boost/utility/value_init.hpp>
|
||||
|
||||
#include <iostream> // For cout.
|
||||
#include <cstdlib> // For EXIT_SUCCESS and EXIT_FAILURE.
|
||||
|
||||
namespace
|
||||
{
|
||||
struct empty_struct
|
||||
{
|
||||
};
|
||||
|
||||
// A POD aggregate struct derived from an empty struct.
|
||||
// Similar to struct Foo1 from Microsoft Visual C++ bug report 484295,
|
||||
// "VC++ does not value-initialize members of derived classes without
|
||||
// user-declared constructor", reported in 2009 by Sylvester Hesp:
|
||||
// https://connect.microsoft.com/VisualStudio/feedback/details/484295
|
||||
struct derived_struct: empty_struct
|
||||
{
|
||||
int data;
|
||||
};
|
||||
|
||||
bool is_value_initialized(const derived_struct& arg)
|
||||
{
|
||||
return arg.data == 0;
|
||||
}
|
||||
|
||||
|
||||
class virtual_destructor_holder
|
||||
{
|
||||
public:
|
||||
int i;
|
||||
virtual ~virtual_destructor_holder()
|
||||
{
|
||||
}
|
||||
};
|
||||
|
||||
bool is_value_initialized(const virtual_destructor_holder& arg)
|
||||
{
|
||||
return arg.i == 0;
|
||||
}
|
||||
|
||||
// Equivalent to the Stats class from GCC Bug 33916,
|
||||
// "Default constructor fails to initialize array members", reported in 2007 by
|
||||
// Michael Elizabeth Chastain: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33916
|
||||
// and fixed for GCC 4.2.4.
|
||||
class private_int_array_pair
|
||||
{
|
||||
friend bool is_value_initialized(const private_int_array_pair& arg);
|
||||
private:
|
||||
int first[12];
|
||||
int second[12];
|
||||
};
|
||||
|
||||
bool is_value_initialized(const private_int_array_pair& arg)
|
||||
{
|
||||
for ( unsigned i = 0; i < 12; ++i)
|
||||
{
|
||||
if ( (arg.first[i] != 0) || (arg.second[i] != 0) )
|
||||
{
|
||||
return false;
|
||||
}
|
||||
}
|
||||
return true;
|
||||
}
|
||||
|
||||
template <typename T>
|
||||
bool is_value_initialized(const T(& arg)[2])
|
||||
{
|
||||
return
|
||||
is_value_initialized(arg[0]) &&
|
||||
is_value_initialized(arg[1]);
|
||||
}
|
||||
|
||||
template <typename T>
|
||||
bool is_value_initialized(const boost::value_initialized<T>& arg)
|
||||
{
|
||||
return is_value_initialized(arg.data());
|
||||
}
|
||||
|
||||
// Returns zero when the specified object is value-initializated, and one otherwise.
|
||||
// Prints a message to standard output if the value-initialization has failed.
|
||||
template <class T>
|
||||
unsigned failed_to_value_initialized(const T& object, const char *const object_name)
|
||||
{
|
||||
if ( is_value_initialized(object) )
|
||||
{
|
||||
return 0u;
|
||||
}
|
||||
else
|
||||
{
|
||||
std::cout << "Note: Failed to value-initialize " << object_name << '.' << std::endl;
|
||||
return 1u;
|
||||
}
|
||||
}
|
||||
|
||||
// A macro that passed both the name and the value of the specified object to
|
||||
// the function above here.
|
||||
#define FAILED_TO_VALUE_INITIALIZE(value) failed_to_value_initialized(value, #value)
|
||||
|
||||
// Equivalent to the dirty_stack() function from GCC Bug 33916,
|
||||
// "Default constructor fails to initialize array members", reported in 2007 by
|
||||
// Michael Elizabeth Chastain: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33916
|
||||
void dirty_stack()
|
||||
{
|
||||
unsigned char array_on_stack[4096];
|
||||
for (unsigned i = 0; i < sizeof(array_on_stack); ++i)
|
||||
{
|
||||
array_on_stack[i] = 0x11;
|
||||
}
|
||||
}
|
||||
|
||||
}
|
||||
|
||||
|
||||
int main()
|
||||
{
|
||||
dirty_stack();
|
||||
|
||||
// TODO More types may be added later.
|
||||
const unsigned num_failures =
|
||||
FAILED_TO_VALUE_INITIALIZE(boost::value_initialized<derived_struct>()) +
|
||||
FAILED_TO_VALUE_INITIALIZE(boost::value_initialized<virtual_destructor_holder[2]>()) +
|
||||
FAILED_TO_VALUE_INITIALIZE(boost::value_initialized<private_int_array_pair>());
|
||||
|
||||
#ifdef BOOST_DETAIL_VALUE_INIT_WORKAROUND_SUGGESTED
|
||||
// One or more failures are expected.
|
||||
return num_failures > 0 ? EXIT_SUCCESS : EXIT_FAILURE;
|
||||
#else
|
||||
// No failures are expected.
|
||||
return num_failures == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
|
||||
#endif
|
||||
}
|
Reference in New Issue
Block a user