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<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
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CLASS="SECT1"
><H1
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><A
NAME="LIBC-THREAD-SAFETY">Thread safety</H1
><P
>The ISO C library has configuration options that control thread
safety, i.e. working behavior if multiple threads call the same
function at the same time.</P
><P
>The following functionality has to be configured correctly,
or used carefully in a multi-threaded environment:</P
><P
></P
><UL
><LI
><P
><TT
CLASS="FUNCTION"
>mblen()</TT
></P
></LI
><LI
><P
><TT
CLASS="FUNCTION"
>mbtowc()</TT
></P
></LI
><LI
><P
><TT
CLASS="FUNCTION"
>wctomb()</TT
></P
></LI
><LI
><P
><TT
CLASS="FUNCTION"
>printf()</TT
>
 (and all standard I/O functions except for
<TT
CLASS="FUNCTION"
>sprintf()</TT
>
 and
<TT
CLASS="FUNCTION"
>sscanf()</TT
></P
></LI
><LI
><P
><TT
CLASS="FUNCTION"
>strtok()</TT
></P
></LI
><LI
><P
><TT
CLASS="FUNCTION"
>rand()</TT
>
 and
<TT
CLASS="FUNCTION"
>srand()</TT
></P
></LI
><LI
><P
><TT
CLASS="FUNCTION"
>signal()</TT
>
 and
<TT
CLASS="FUNCTION"
>raise()</TT
></P
></LI
><LI
><P
><TT
CLASS="FUNCTION"
>asctime()</TT
>
,
<TT
CLASS="FUNCTION"
>ctime()</TT
>
,
<TT
CLASS="FUNCTION"
>gmtime()</TT
>
, and
<TT
CLASS="FUNCTION"
>localtime()</TT
></P
></LI
><LI
><P
>the
<TT
CLASS="FUNCTION"
>errno</TT
>
 variable</P
></LI
><LI
><P
>the
<TT
CLASS="FUNCTION"
>environ</TT
>
 variable</P
></LI
><LI
><P
>date and time settings</P
></LI
></UL
><P
>In some cases, to make <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>eCos</I
></SPAN
> development
easier, functions are provided (as specified by POSIX 1003.1) that define
re-entrant alternatives, i.e. <TT
CLASS="FUNCTION"
>rand_r()</TT
>, <TT
CLASS="FUNCTION"
>strtok_r()</TT
>, <TT
CLASS="FUNCTION"
>asctime_r()</TT
>, <TT
CLASS="FUNCTION"
>ctime_r()</TT
>, <TT
CLASS="FUNCTION"
>gmtime_r()</TT
>,
and <TT
CLASS="FUNCTION"
>localtime_r()</TT
>. In other cases,
configuration options are provided that control either locking of functions
or their shared data, such as with standard I/O streams,
or by using per-thread data, such as with the <TT
CLASS="FUNCTION"
>errno</TT
> variable.</P
><P
>In some other cases, like the setting of date and time, no
re-entrant or thread-safe alternative or configuration is provided
as it is simply not a worthwhile addition (date and time should
rarely need to be set.)</P
></DIV
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1	28	unneback	`<!-- Copyright (C) 2003 Red Hat, Inc. -->`
2			`<!-- This material may be distributed only subject to the terms -->`
3			`<!-- and conditions set forth in the Open Publication License, v1.0 -->`
4			`<!-- or later (the latest version is presently available at -->`
5			`<!-- http://www.opencontent.org/openpub/). -->`
6			`<!-- Distribution of the work or derivative of the work in any -->`
7			`<!-- standard (paper) book form is prohibited unless prior -->`
8			`<!-- permission is obtained from the copyright holder. -->`
9			`<HTML`
10			`><HEAD`
11			`><TITLE`
12			`>Thread safety</TITLE`
13			`><meta name="MSSmartTagsPreventParsing" content="TRUE">`
14			`<META`
15			`NAME="GENERATOR"`
16			`CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+`
17			`"><LINK`
18			`REL="HOME"`
19			`TITLE="eCos Reference Manual"`
20			`HREF="ecos-ref.html"><LINK`
21			`REL="UP"`
22			`TITLE="C and math library overview"`
23			`HREF="c-and-math-library-overview.html"><LINK`
24			`REL="PREVIOUS"`
25			`TITLE="Some implementation details"`
26			`HREF="libc-implementation-details.html"><LINK`
27			`REL="NEXT"`
28			`TITLE="C library startup"`
29			`HREF="c-library-startup.html"></HEAD`
30			`><BODY`
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41			`WIDTH="100%"`
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44			`CELLSPACING="0"`
45			`><TR`
46			`><TH`
47			`COLSPAN="3"`
48			`ALIGN="center"`
49			`>eCos Reference Manual</TH`
50			`></TR`
51			`><TR`
52			`><TD`
53			`WIDTH="10%"`
54			`ALIGN="left"`
55			`VALIGN="bottom"`
56			`><A`
57			`HREF="libc-implementation-details.html"`
58			`ACCESSKEY="P"`
59			`>Prev</A`
60			`></TD`
61			`><TD`
62			`WIDTH="80%"`
63			`ALIGN="center"`
64			`VALIGN="bottom"`
65			`>Chapter 13. C and math library overview</TD`
66			`><TD`
67			`WIDTH="10%"`
68			`ALIGN="right"`
69			`VALIGN="bottom"`
70			`><A`
71			`HREF="c-library-startup.html"`
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73			`>Next</A`
74			`></TD`
75			`></TR`
76			`></TABLE`
77			`><HR`
78			`ALIGN="LEFT"`
79			`WIDTH="100%"></DIV`
80			`><DIV`
81			`CLASS="SECT1"`
82			`><H1`
83			`CLASS="SECT1"`
84			`><A`
85			`NAME="LIBC-THREAD-SAFETY">Thread safety</H1`
86			`><P`
87			`>The ISO C library has configuration options that control thread`
88			`safety, i.e. working behavior if multiple threads call the same`
89			`function at the same time.</P`
90			`><P`
91			`>The following functionality has to be configured correctly,`
92			`or used carefully in a multi-threaded environment:</P`
93			`><P`
94			`></P`
95			`><UL`
96			`><LI`
97			`><P`
98			`><TT`
99			`CLASS="FUNCTION"`
100			`>mblen()</TT`
101			`></P`
102			`></LI`
103			`><LI`
104			`><P`
105			`><TT`
106			`CLASS="FUNCTION"`
107			`>mbtowc()</TT`
108			`></P`
109			`></LI`
110			`><LI`
111			`><P`
112			`><TT`
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114			`>wctomb()</TT`
115			`></P`
116			`></LI`
117			`><LI`
118			`><P`
119			`><TT`
120			`CLASS="FUNCTION"`
121			`>printf()</TT`
122			`>`
123			`(and all standard I/O functions except for`
124			`<TT`
125			`CLASS="FUNCTION"`
126			`>sprintf()</TT`
127			`>`
128			`and`
129			`<TT`
130			`CLASS="FUNCTION"`
131			`>sscanf()</TT`
132			`></P`
133			`></LI`
134			`><LI`
135			`><P`
136			`><TT`
137			`CLASS="FUNCTION"`
138			`>strtok()</TT`
139			`></P`
140			`></LI`
141			`><LI`
142			`><P`
143			`><TT`
144			`CLASS="FUNCTION"`
145			`>rand()</TT`
146			`>`
147			`and`
148			`<TT`
149			`CLASS="FUNCTION"`
150			`>srand()</TT`
151			`></P`
152			`></LI`
153			`><LI`
154			`><P`
155			`><TT`
156			`CLASS="FUNCTION"`
157			`>signal()</TT`
158			`>`
159			`and`
160			`<TT`
161			`CLASS="FUNCTION"`
162			`>raise()</TT`
163			`></P`
164			`></LI`
165			`><LI`
166			`><P`
167			`><TT`
168			`CLASS="FUNCTION"`
169			`>asctime()</TT`
170			`>`
171			`,`
172			`<TT`
173			`CLASS="FUNCTION"`
174			`>ctime()</TT`
175			`>`
176			`,`
177			`<TT`
178			`CLASS="FUNCTION"`
179			`>gmtime()</TT`
180			`>`
181			`, and`
182			`<TT`
183			`CLASS="FUNCTION"`
184			`>localtime()</TT`
185			`></P`
186			`></LI`
187			`><LI`
188			`><P`
189			`>the`
190			`<TT`
191			`CLASS="FUNCTION"`
192			`>errno</TT`
193			`>`
194			`variable</P`
195			`></LI`
196			`><LI`
197			`><P`
198			`>the`
199			`<TT`
200			`CLASS="FUNCTION"`
201			`>environ</TT`
202			`>`
203			`variable</P`
204			`></LI`
205			`><LI`
206			`><P`
207			`>date and time settings</P`
208			`></LI`
209			`></UL`
210			`><P`
211			`>In some cases, to make <SPAN`
212			`CLASS="emphasis"`
213			`><I`
214			`CLASS="EMPHASIS"`
215			`>eCos</I`
216			`></SPAN`
217			`> development`
218			`easier, functions are provided (as specified by POSIX 1003.1) that define`
219			`re-entrant alternatives, i.e. <TT`
220			`CLASS="FUNCTION"`
221			`>rand_r()</TT`
222			`>, <TT`
223			`CLASS="FUNCTION"`
224			`>strtok_r()</TT`
225			`>, <TT`
226			`CLASS="FUNCTION"`
227			`>asctime_r()</TT`
228			`>, <TT`
229			`CLASS="FUNCTION"`
230			`>ctime_r()</TT`
231			`>, <TT`
232			`CLASS="FUNCTION"`
233			`>gmtime_r()</TT`
234			`>,`
235			`and <TT`
236			`CLASS="FUNCTION"`
237			`>localtime_r()</TT`
238			`>. In other cases,`
239			`configuration options are provided that control either locking of functions`
240			`or their shared data, such as with standard I/O streams,`
241			`or by using per-thread data, such as with the <TT`
242			`CLASS="FUNCTION"`
243			`>errno</TT`
244			`> variable.</P`
245			`><P`
246			`>In some other cases, like the setting of date and time, no`
247			`re-entrant or thread-safe alternative or configuration is provided`
248			`as it is simply not a worthwhile addition (date and time should`
249			`rarely need to be set.)</P`
250			`></DIV`
251			`><DIV`
252			`CLASS="NAVFOOTER"`
253			`><HR`
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268			`ACCESSKEY="P"`
269			`>Prev</A`
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278			`>Home</A`
279			`></TD`
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295			`>Some implementation details</TD`
296			`><TD`
297			`WIDTH="34%"`
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299			`VALIGN="top"`
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