<!-- Copyright (C) 2003 Red Hat, Inc. -->
|
<!-- Copyright (C) 2003 Red Hat, Inc. -->
|
<!-- This material may be distributed only subject to the terms -->
|
<!-- This material may be distributed only subject to the terms -->
|
<!-- and conditions set forth in the Open Publication License, v1.0 -->
|
<!-- and conditions set forth in the Open Publication License, v1.0 -->
|
<!-- or later (the latest version is presently available at -->
|
<!-- or later (the latest version is presently available at -->
|
<!-- http://www.opencontent.org/openpub/). -->
|
<!-- http://www.opencontent.org/openpub/). -->
|
<!-- Distribution of the work or derivative of the work in any -->
|
<!-- Distribution of the work or derivative of the work in any -->
|
<!-- standard (paper) book form is prohibited unless prior -->
|
<!-- standard (paper) book form is prohibited unless prior -->
|
<!-- permission is obtained from the copyright holder. -->
|
<!-- permission is obtained from the copyright holder. -->
|
<HTML
|
<HTML
|
><HEAD
|
><HEAD
|
><TITLE
|
><TITLE
|
>Thread safety</TITLE
|
>Thread safety</TITLE
|
><meta name="MSSmartTagsPreventParsing" content="TRUE">
|
><meta name="MSSmartTagsPreventParsing" content="TRUE">
|
<META
|
<META
|
NAME="GENERATOR"
|
NAME="GENERATOR"
|
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
|
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
|
"><LINK
|
"><LINK
|
REL="HOME"
|
REL="HOME"
|
TITLE="eCos Reference Manual"
|
TITLE="eCos Reference Manual"
|
HREF="ecos-ref.html"><LINK
|
HREF="ecos-ref.html"><LINK
|
REL="UP"
|
REL="UP"
|
TITLE="C and math library overview"
|
TITLE="C and math library overview"
|
HREF="c-and-math-library-overview.html"><LINK
|
HREF="c-and-math-library-overview.html"><LINK
|
REL="PREVIOUS"
|
REL="PREVIOUS"
|
TITLE="Some implementation details"
|
TITLE="Some implementation details"
|
HREF="libc-implementation-details.html"><LINK
|
HREF="libc-implementation-details.html"><LINK
|
REL="NEXT"
|
REL="NEXT"
|
TITLE="C library startup"
|
TITLE="C library startup"
|
HREF="c-library-startup.html"></HEAD
|
HREF="c-library-startup.html"></HEAD
|
><BODY
|
><BODY
|
CLASS="SECT1"
|
CLASS="SECT1"
|
BGCOLOR="#FFFFFF"
|
BGCOLOR="#FFFFFF"
|
TEXT="#000000"
|
TEXT="#000000"
|
LINK="#0000FF"
|
LINK="#0000FF"
|
VLINK="#840084"
|
VLINK="#840084"
|
ALINK="#0000FF"
|
ALINK="#0000FF"
|
><DIV
|
><DIV
|
CLASS="NAVHEADER"
|
CLASS="NAVHEADER"
|
><TABLE
|
><TABLE
|
SUMMARY="Header navigation table"
|
SUMMARY="Header navigation table"
|
WIDTH="100%"
|
WIDTH="100%"
|
BORDER="0"
|
BORDER="0"
|
CELLPADDING="0"
|
CELLPADDING="0"
|
CELLSPACING="0"
|
CELLSPACING="0"
|
><TR
|
><TR
|
><TH
|
><TH
|
COLSPAN="3"
|
COLSPAN="3"
|
ALIGN="center"
|
ALIGN="center"
|
>eCos Reference Manual</TH
|
>eCos Reference Manual</TH
|
></TR
|
></TR
|
><TR
|
><TR
|
><TD
|
><TD
|
WIDTH="10%"
|
WIDTH="10%"
|
ALIGN="left"
|
ALIGN="left"
|
VALIGN="bottom"
|
VALIGN="bottom"
|
><A
|
><A
|
HREF="libc-implementation-details.html"
|
HREF="libc-implementation-details.html"
|
ACCESSKEY="P"
|
ACCESSKEY="P"
|
>Prev</A
|
>Prev</A
|
></TD
|
></TD
|
><TD
|
><TD
|
WIDTH="80%"
|
WIDTH="80%"
|
ALIGN="center"
|
ALIGN="center"
|
VALIGN="bottom"
|
VALIGN="bottom"
|
>Chapter 13. C and math library overview</TD
|
>Chapter 13. C and math library overview</TD
|
><TD
|
><TD
|
WIDTH="10%"
|
WIDTH="10%"
|
ALIGN="right"
|
ALIGN="right"
|
VALIGN="bottom"
|
VALIGN="bottom"
|
><A
|
><A
|
HREF="c-library-startup.html"
|
HREF="c-library-startup.html"
|
ACCESSKEY="N"
|
ACCESSKEY="N"
|
>Next</A
|
>Next</A
|
></TD
|
></TD
|
></TR
|
></TR
|
></TABLE
|
></TABLE
|
><HR
|
><HR
|
ALIGN="LEFT"
|
ALIGN="LEFT"
|
WIDTH="100%"></DIV
|
WIDTH="100%"></DIV
|
><DIV
|
><DIV
|
CLASS="SECT1"
|
CLASS="SECT1"
|
><H1
|
><H1
|
CLASS="SECT1"
|
CLASS="SECT1"
|
><A
|
><A
|
NAME="LIBC-THREAD-SAFETY">Thread safety</H1
|
NAME="LIBC-THREAD-SAFETY">Thread safety</H1
|
><P
|
><P
|
>The ISO C library has configuration options that control thread
|
>The ISO C library has configuration options that control thread
|
safety, i.e. working behavior if multiple threads call the same
|
safety, i.e. working behavior if multiple threads call the same
|
function at the same time.</P
|
function at the same time.</P
|
><P
|
><P
|
>The following functionality has to be configured correctly,
|
>The following functionality has to be configured correctly,
|
or used carefully in a multi-threaded environment:</P
|
or used carefully in a multi-threaded environment:</P
|
><P
|
><P
|
></P
|
></P
|
><UL
|
><UL
|
><LI
|
><LI
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>mblen()</TT
|
>mblen()</TT
|
></P
|
></P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>mbtowc()</TT
|
>mbtowc()</TT
|
></P
|
></P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>wctomb()</TT
|
>wctomb()</TT
|
></P
|
></P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>printf()</TT
|
>printf()</TT
|
>
|
>
|
(and all standard I/O functions except for
|
(and all standard I/O functions except for
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>sprintf()</TT
|
>sprintf()</TT
|
>
|
>
|
and
|
and
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>sscanf()</TT
|
>sscanf()</TT
|
></P
|
></P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>strtok()</TT
|
>strtok()</TT
|
></P
|
></P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>rand()</TT
|
>rand()</TT
|
>
|
>
|
and
|
and
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>srand()</TT
|
>srand()</TT
|
></P
|
></P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>signal()</TT
|
>signal()</TT
|
>
|
>
|
and
|
and
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>raise()</TT
|
>raise()</TT
|
></P
|
></P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>asctime()</TT
|
>asctime()</TT
|
>
|
>
|
,
|
,
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>ctime()</TT
|
>ctime()</TT
|
>
|
>
|
,
|
,
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>gmtime()</TT
|
>gmtime()</TT
|
>
|
>
|
, and
|
, and
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>localtime()</TT
|
>localtime()</TT
|
></P
|
></P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
>the
|
>the
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>errno</TT
|
>errno</TT
|
>
|
>
|
variable</P
|
variable</P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
>the
|
>the
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>environ</TT
|
>environ</TT
|
>
|
>
|
variable</P
|
variable</P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
>date and time settings</P
|
>date and time settings</P
|
></LI
|
></LI
|
></UL
|
></UL
|
><P
|
><P
|
>In some cases, to make <SPAN
|
>In some cases, to make <SPAN
|
CLASS="emphasis"
|
CLASS="emphasis"
|
><I
|
><I
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>eCos</I
|
>eCos</I
|
></SPAN
|
></SPAN
|
> development
|
> development
|
easier, functions are provided (as specified by POSIX 1003.1) that define
|
easier, functions are provided (as specified by POSIX 1003.1) that define
|
re-entrant alternatives, i.e. <TT
|
re-entrant alternatives, i.e. <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>rand_r()</TT
|
>rand_r()</TT
|
>, <TT
|
>, <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>strtok_r()</TT
|
>strtok_r()</TT
|
>, <TT
|
>, <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>asctime_r()</TT
|
>asctime_r()</TT
|
>, <TT
|
>, <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>ctime_r()</TT
|
>ctime_r()</TT
|
>, <TT
|
>, <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>gmtime_r()</TT
|
>gmtime_r()</TT
|
>,
|
>,
|
and <TT
|
and <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>localtime_r()</TT
|
>localtime_r()</TT
|
>. In other cases,
|
>. In other cases,
|
configuration options are provided that control either locking of functions
|
configuration options are provided that control either locking of functions
|
or their shared data, such as with standard I/O streams,
|
or their shared data, such as with standard I/O streams,
|
or by using per-thread data, such as with the <TT
|
or by using per-thread data, such as with the <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>errno</TT
|
>errno</TT
|
> variable.</P
|
> variable.</P
|
><P
|
><P
|
>In some other cases, like the setting of date and time, no
|
>In some other cases, like the setting of date and time, no
|
re-entrant or thread-safe alternative or configuration is provided
|
re-entrant or thread-safe alternative or configuration is provided
|
as it is simply not a worthwhile addition (date and time should
|
as it is simply not a worthwhile addition (date and time should
|
rarely need to be set.)</P
|
rarely need to be set.)</P
|
></DIV
|
></DIV
|
><DIV
|
><DIV
|
CLASS="NAVFOOTER"
|
CLASS="NAVFOOTER"
|
><HR
|
><HR
|
ALIGN="LEFT"
|
ALIGN="LEFT"
|
WIDTH="100%"><TABLE
|
WIDTH="100%"><TABLE
|
SUMMARY="Footer navigation table"
|
SUMMARY="Footer navigation table"
|
WIDTH="100%"
|
WIDTH="100%"
|
BORDER="0"
|
BORDER="0"
|
CELLPADDING="0"
|
CELLPADDING="0"
|
CELLSPACING="0"
|
CELLSPACING="0"
|
><TR
|
><TR
|
><TD
|
><TD
|
WIDTH="33%"
|
WIDTH="33%"
|
ALIGN="left"
|
ALIGN="left"
|
VALIGN="top"
|
VALIGN="top"
|
><A
|
><A
|
HREF="libc-implementation-details.html"
|
HREF="libc-implementation-details.html"
|
ACCESSKEY="P"
|
ACCESSKEY="P"
|
>Prev</A
|
>Prev</A
|
></TD
|
></TD
|
><TD
|
><TD
|
WIDTH="34%"
|
WIDTH="34%"
|
ALIGN="center"
|
ALIGN="center"
|
VALIGN="top"
|
VALIGN="top"
|
><A
|
><A
|
HREF="ecos-ref.html"
|
HREF="ecos-ref.html"
|
ACCESSKEY="H"
|
ACCESSKEY="H"
|
>Home</A
|
>Home</A
|
></TD
|
></TD
|
><TD
|
><TD
|
WIDTH="33%"
|
WIDTH="33%"
|
ALIGN="right"
|
ALIGN="right"
|
VALIGN="top"
|
VALIGN="top"
|
><A
|
><A
|
HREF="c-library-startup.html"
|
HREF="c-library-startup.html"
|
ACCESSKEY="N"
|
ACCESSKEY="N"
|
>Next</A
|
>Next</A
|
></TD
|
></TD
|
></TR
|
></TR
|
><TR
|
><TR
|
><TD
|
><TD
|
WIDTH="33%"
|
WIDTH="33%"
|
ALIGN="left"
|
ALIGN="left"
|
VALIGN="top"
|
VALIGN="top"
|
>Some implementation details</TD
|
>Some implementation details</TD
|
><TD
|
><TD
|
WIDTH="34%"
|
WIDTH="34%"
|
ALIGN="center"
|
ALIGN="center"
|
VALIGN="top"
|
VALIGN="top"
|
><A
|
><A
|
HREF="c-and-math-library-overview.html"
|
HREF="c-and-math-library-overview.html"
|
ACCESSKEY="U"
|
ACCESSKEY="U"
|
>Up</A
|
>Up</A
|
></TD
|
></TD
|
><TD
|
><TD
|
WIDTH="33%"
|
WIDTH="33%"
|
ALIGN="right"
|
ALIGN="right"
|
VALIGN="top"
|
VALIGN="top"
|
>C library startup</TD
|
>C library startup</TD
|
></TR
|
></TR
|
></TABLE
|
></TABLE
|
></DIV
|
></DIV
|
></BODY
|
></BODY
|
></HTML
|
></HTML
|
|
|
