1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Thread Local Storage</title>
<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset">
<link rel="up" href="../thread.html" title="Chapter 38. Thread 4.7.2">
<link rel="prev" href="synchronization.html" title="Synchronization">
<link rel="next" href="sds.html" title="Synchronized Data Structures">
</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">
<a accesskey="p" href="synchronization.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../thread.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="sds.html"><img src="../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="thread.thread_local_storage"></a><a class="link" href="thread_local_storage.html" title="Thread Local Storage">Thread Local Storage</a>
</h2></div></div></div>
<div class="toc"><dl class="toc"><dt><span class="section"><a href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr">Class
<code class="computeroutput"><span class="identifier">thread_specific_ptr</span></code></a></span></dt></dl></div>
<h4>
<a name="thread.thread_local_storage.h0"></a>
<span class="phrase"><a name="thread.thread_local_storage.synopsis"></a></span><a class="link" href="thread_local_storage.html#thread.thread_local_storage.synopsis">Synopsis</a>
</h4>
<p>
Thread local storage allows multi-threaded applications to have a separate
instance of a given data item for each thread. Where a single-threaded application
would use static or global data, this could lead to contention, deadlock or
data corruption in a multi-threaded application. One example is the C <code class="computeroutput"><span class="identifier">errno</span></code> variable, used for storing the error
code related to functions from the Standard C library. It is common practice
(and required by POSIX) for compilers that support multi-threaded applications
to provide a separate instance of <code class="computeroutput"><span class="identifier">errno</span></code>
for each thread, in order to avoid different threads competing to read or update
the value.
</p>
<p>
Though compilers often provide this facility in the form of extensions to the
declaration syntax (such as <code class="computeroutput"><span class="identifier">__declspec</span><span class="special">(</span><span class="identifier">thread</span><span class="special">)</span></code>
or <code class="computeroutput"><a class="link" href="thread_management.html#thread.thread_management.thread" title="Class thread"><code class="computeroutput"><span class="identifier">thread</span></code></a></code>
annotations on <code class="computeroutput"><span class="keyword">static</span></code> or namespace-scope
variable declarations), such support is non-portable, and is often limited
in some way, such as only supporting POD types.
</p>
<h4>
<a name="thread.thread_local_storage.h1"></a>
<span class="phrase"><a name="thread.thread_local_storage.portable_thread_local_storage_with__code__phrase_role__identifier__boost__phrase__phrase_role__special______phrase__phrase_role__identifier__thread_specific_ptr__phrase___code_"></a></span><a class="link" href="thread_local_storage.html#thread.thread_local_storage.portable_thread_local_storage_with__code__phrase_role__identifier__boost__phrase__phrase_role__special______phrase__phrase_role__identifier__thread_specific_ptr__phrase___code_">Portable
thread-local storage with <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_specific_ptr</span></code></a>
</h4>
<p>
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_specific_ptr</span></code> provides a portable mechanism
for thread-local storage that works on all compilers supported by <span class="bold"><strong>Boost.Thread</strong></span>. Each instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_specific_ptr</span></code>
represents a pointer to an object (such as <code class="computeroutput"><span class="identifier">errno</span></code>)
where each thread must have a distinct value. The value for the current thread
can be obtained using the <code class="computeroutput"><span class="identifier">get</span><span class="special">()</span></code> member function, or by using the <code class="computeroutput"><span class="special">*</span></code> and <code class="computeroutput"><span class="special">-></span></code>
pointer deference operators. Initially the pointer has a value of <code class="computeroutput"><span class="identifier">NULL</span></code> in each thread, but the value for the
current thread can be set using the <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code> member function.
</p>
<p>
If the value of the pointer for the current thread is changed using <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code>,
then the previous value is destroyed by calling the cleanup routine. Alternatively,
the stored value can be reset to <code class="computeroutput"><span class="identifier">NULL</span></code>
and the prior value returned by calling the <code class="computeroutput"><span class="identifier">release</span><span class="special">()</span></code> member function, allowing the application
to take back responsibility for destroying the object.
</p>
<h4>
<a name="thread.thread_local_storage.h2"></a>
<span class="phrase"><a name="thread.thread_local_storage.cleanup_at_thread_exit"></a></span><a class="link" href="thread_local_storage.html#thread.thread_local_storage.cleanup_at_thread_exit">Cleanup
at thread exit</a>
</h4>
<p>
When a thread exits, the objects associated with each <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_specific_ptr</span></code>
instance are destroyed. By default, the object pointed to by a pointer <code class="computeroutput"><span class="identifier">p</span></code> is destroyed by invoking <code class="computeroutput"><span class="keyword">delete</span> <span class="identifier">p</span></code>,
but this can be overridden for a specific instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_specific_ptr</span></code>
by providing a cleanup routine to the constructor. In this case, the object
is destroyed by invoking <code class="computeroutput"><span class="identifier">func</span><span class="special">(</span><span class="identifier">p</span><span class="special">)</span></code>
where <code class="computeroutput"><span class="identifier">func</span></code> is the cleanup routine
supplied to the constructor. The cleanup functions are called in an unspecified
order. If a cleanup routine sets the value of associated with an instance of
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_specific_ptr</span></code> that has already been
cleaned up, that value is added to the cleanup list. Cleanup finishes when
there are no outstanding instances of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_specific_ptr</span></code>
with values.
</p>
<p>
Note: on some platforms, cleanup of thread-specific data is not performed for
threads created with the platform's native API. On those platforms such cleanup
is only done for threads that are started with <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span></code>
unless <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">on_thread_exit</span><span class="special">()</span></code>
is called manually from that thread.
</p>
<h4>
<a name="thread.thread_local_storage.h3"></a>
<span class="phrase"><a name="thread.thread_local_storage.rationale_about_the_nature_of_the_key"></a></span><a class="link" href="thread_local_storage.html#thread.thread_local_storage.rationale_about_the_nature_of_the_key">Rationale
about the nature of the key</a>
</h4>
<p>
Boost.Thread uses the address of the <code class="computeroutput"><span class="identifier">thread_specific_ptr</span></code>
instance as key of the thread specific pointers. This avoids to create/destroy
a key which will need a lock to protect from race conditions. This has a little
performance liability, as the access must be done using an associative container.
</p>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="thread.thread_local_storage.thread_specific_ptr"></a><a class="link" href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr" title="Class thread_specific_ptr">Class
<code class="computeroutput"><span class="identifier">thread_specific_ptr</span></code></a>
</h3></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.default_constructor"><code class="computeroutput"><span class="identifier">thread_specific_ptr</span><span class="special">();</span></code></a></span></dt>
<dt><span class="section"><a href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.constructor_with_custom_cleanup"><code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">thread_specific_ptr</span><span class="special">(</span><span class="keyword">void</span> <span class="special">(*</span><span class="identifier">cleanup_function</span><span class="special">)(</span><span class="identifier">T</span><span class="special">*));</span></code></a></span></dt>
<dt><span class="section"><a href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.destructor"><code class="computeroutput"><span class="special">~</span><span class="identifier">thread_specific_ptr</span><span class="special">();</span></code></a></span></dt>
<dt><span class="section"><a href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.get"><code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span></code></a></span></dt>
<dt><span class="section"><a href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.operator_arrow"><code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span><span class="special">->()</span> <span class="keyword">const</span><span class="special">;</span></code></a></span></dt>
<dt><span class="section"><a href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.operator_star"><code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*()</span> <span class="keyword">const</span><span class="special">;</span></code></a></span></dt>
<dt><span class="section"><a href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.reset"><code class="computeroutput"><span class="keyword">void</span> <span class="identifier">reset</span><span class="special">(</span><span class="identifier">T</span><span class="special">*</span>
<span class="identifier">new_value</span><span class="special">=</span><span class="number">0</span><span class="special">);</span></code></a></span></dt>
<dt><span class="section"><a href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.release"><code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> <span class="identifier">release</span><span class="special">();</span></code></a></span></dt>
</dl></div>
<pre class="programlisting"><span class="comment">// #include <boost/thread/tss.hpp></span>
<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">class</span> <span class="identifier">thread_specific_ptr</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="identifier">thread_specific_ptr</span><span class="special">();</span>
<span class="keyword">explicit</span> <span class="identifier">thread_specific_ptr</span><span class="special">(</span><span class="keyword">void</span> <span class="special">(*</span><span class="identifier">cleanup_function</span><span class="special">)(</span><span class="identifier">T</span><span class="special">*));</span>
<span class="special">~</span><span class="identifier">thread_specific_ptr</span><span class="special">();</span>
<span class="identifier">T</span><span class="special">*</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span>
<span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span><span class="special">->()</span> <span class="keyword">const</span><span class="special">;</span>
<span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*()</span> <span class="keyword">const</span><span class="special">;</span>
<span class="identifier">T</span><span class="special">*</span> <span class="identifier">release</span><span class="special">();</span>
<span class="keyword">void</span> <span class="identifier">reset</span><span class="special">(</span><span class="identifier">T</span><span class="special">*</span> <span class="identifier">new_value</span><span class="special">=</span><span class="number">0</span><span class="special">);</span>
<span class="special">};</span>
<span class="special">}</span>
</pre>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="thread.thread_local_storage.thread_specific_ptr.default_constructor"></a><a class="link" href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.default_constructor" title="thread_specific_ptr();"><code class="computeroutput"><span class="identifier">thread_specific_ptr</span><span class="special">();</span></code></a>
</h4></div></div></div>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Requires:</span></dt>
<dd><p>
<code class="computeroutput"><span class="keyword">delete</span> <span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">()</span></code> is well-formed.
</p></dd>
<dt><span class="term">Effects:</span></dt>
<dd><p>
Construct a <code class="computeroutput"><span class="identifier">thread_specific_ptr</span></code>
object for storing a pointer to an object of type <code class="computeroutput"><span class="identifier">T</span></code>
specific to each thread. The default <code class="computeroutput"><span class="keyword">delete</span></code>-based
cleanup function will be used to destroy any thread-local objects
when <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code>
is called, or the thread exits.
</p></dd>
<dt><span class="term">Throws:</span></dt>
<dd><p>
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_resource_error</span></code> if an error
occurs.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="thread.thread_local_storage.thread_specific_ptr.constructor_with_custom_cleanup"></a><a class="link" href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.constructor_with_custom_cleanup" title="explicit thread_specific_ptr(void (*cleanup_function)(T*));"><code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">thread_specific_ptr</span><span class="special">(</span><span class="keyword">void</span> <span class="special">(*</span><span class="identifier">cleanup_function</span><span class="special">)(</span><span class="identifier">T</span><span class="special">*));</span></code></a>
</h4></div></div></div>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Requires:</span></dt>
<dd><p>
<code class="computeroutput"><span class="identifier">cleanup_function</span><span class="special">(</span><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">())</span></code> does not throw any exceptions.
</p></dd>
<dt><span class="term">Effects:</span></dt>
<dd><p>
Construct a <code class="computeroutput"><span class="identifier">thread_specific_ptr</span></code>
object for storing a pointer to an object of type <code class="computeroutput"><span class="identifier">T</span></code>
specific to each thread. The supplied <code class="computeroutput"><span class="identifier">cleanup_function</span></code>
will be used to destroy any thread-local objects when <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code>
is called, or the thread exits.
</p></dd>
<dt><span class="term">Throws:</span></dt>
<dd><p>
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_resource_error</span></code> if an error
occurs.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="thread.thread_local_storage.thread_specific_ptr.destructor"></a><a class="link" href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.destructor" title="~thread_specific_ptr();"><code class="computeroutput"><span class="special">~</span><span class="identifier">thread_specific_ptr</span><span class="special">();</span></code></a>
</h4></div></div></div>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Requires:</span></dt>
<dd><p>
All the thread specific instances associated to this thread_specific_ptr
(except maybe the one associated to this thread) must be null.
</p></dd>
<dt><span class="term">Effects:</span></dt>
<dd><p>
Calls <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">reset</span><span class="special">()</span></code>
to clean up the associated value for the current thread, and destroys
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
</p></dd>
<dt><span class="term">Throws:</span></dt>
<dd><p>
Nothing.
</p></dd>
<dt><span class="term">Remarks:</span></dt>
<dd><p>
The requirement is due to the fact that in order to delete all these
instances, the implementation should be forced to maintain a list
of all the threads having an associated specific ptr, which is against
the goal of thread specific data.
</p></dd>
</dl>
</div>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
Care needs to be taken to ensure that any threads still running after
an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_specific_ptr</span></code>
has been destroyed do not call any member functions on that instance.
</p></td></tr>
</table></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="thread.thread_local_storage.thread_specific_ptr.get"></a><a class="link" href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.get" title="T* get() const;"><code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span></code></a>
</h4></div></div></div>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Returns:</span></dt>
<dd><p>
The pointer associated with the current thread.
</p></dd>
<dt><span class="term">Throws:</span></dt>
<dd><p>
Nothing.
</p></dd>
</dl>
</div>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
The initial value associated with an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_specific_ptr</span></code>
is <code class="computeroutput"><span class="identifier">NULL</span></code> for each thread.
</p></td></tr>
</table></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="thread.thread_local_storage.thread_specific_ptr.operator_arrow"></a><a class="link" href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.operator_arrow" title="T* operator->() const;"><code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span><span class="special">->()</span> <span class="keyword">const</span><span class="special">;</span></code></a>
</h4></div></div></div>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Returns:</span></dt>
<dd><p>
<code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">()</span></code>
</p></dd>
<dt><span class="term">Throws:</span></dt>
<dd><p>
Nothing.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="thread.thread_local_storage.thread_specific_ptr.operator_star"></a><a class="link" href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.operator_star" title="T& operator*() const;"><code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*()</span> <span class="keyword">const</span><span class="special">;</span></code></a>
</h4></div></div></div>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Requires:</span></dt>
<dd><p>
<code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span></code> is not <code class="computeroutput"><span class="identifier">NULL</span></code>.
</p></dd>
<dt><span class="term">Returns:</span></dt>
<dd><p>
<code class="computeroutput"><span class="special">*(</span><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">())</span></code>
</p></dd>
<dt><span class="term">Throws:</span></dt>
<dd><p>
Nothing.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="thread.thread_local_storage.thread_specific_ptr.reset"></a><a class="link" href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.reset" title="void reset(T* new_value=0);"><code class="computeroutput"><span class="keyword">void</span> <span class="identifier">reset</span><span class="special">(</span><span class="identifier">T</span><span class="special">*</span>
<span class="identifier">new_value</span><span class="special">=</span><span class="number">0</span><span class="special">);</span></code></a>
</h4></div></div></div>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Effects:</span></dt>
<dd><p>
If <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">()!=</span><span class="identifier">new_value</span></code> and <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">()</span></code> is non-<code class="computeroutput"><span class="identifier">NULL</span></code>,
invoke <code class="computeroutput"><span class="keyword">delete</span> <span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">()</span></code> or <code class="computeroutput"><span class="identifier">cleanup_function</span><span class="special">(</span><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">())</span></code> as appropriate. Store <code class="computeroutput"><span class="identifier">new_value</span></code> as the pointer associated
with the current thread.
</p></dd>
<dt><span class="term">Postcondition:</span></dt>
<dd><p>
<code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">()==</span><span class="identifier">new_value</span></code>
</p></dd>
<dt><span class="term">Throws:</span></dt>
<dd><p>
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread_resource_error</span></code> if an error
occurs.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="thread.thread_local_storage.thread_specific_ptr.release"></a><a class="link" href="thread_local_storage.html#thread.thread_local_storage.thread_specific_ptr.release" title="T* release();"><code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> <span class="identifier">release</span><span class="special">();</span></code></a>
</h4></div></div></div>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Effects:</span></dt>
<dd><p>
Return <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">()</span></code>
and store <code class="computeroutput"><span class="identifier">NULL</span></code> as
the pointer associated with the current thread without invoking the
cleanup function.
</p></dd>
<dt><span class="term">Postcondition:</span></dt>
<dd><p>
<code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">get</span><span class="special">()==</span><span class="number">0</span></code>
</p></dd>
<dt><span class="term">Throws:</span></dt>
<dd><p>
Nothing.
</p></dd>
</dl>
</div>
</div>
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2007 -11 Anthony Williams<br>Copyright © 2011 -16 Vicente J. Botet Escriba<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></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="synchronization.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../thread.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="sds.html"><img src="../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
|
