155 lines
3.8 KiB
HTML
155 lines
3.8 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of ASSERT</TITLE>
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</HEAD><BODY>
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<H1>ASSERT</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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assert - abort the program if assertion is false
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/assert.h">assert.h</A>></B>
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<B>void assert(scalar </B><I>expression</I><B>);</B>
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</PRE>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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This macro can help programmers find bugs in their programs,
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or handle exceptional cases
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via a crash that will produce limited debugging output.
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<P>
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If
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<I>expression</I>
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is false (i.e., compares equal to zero),
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<B>assert</B>()
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prints an error message to standard error
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and terminates the program by calling
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<B><A HREF="/cgi-bin/man/man2html?3+abort">abort</A></B>(3).
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The error message includes the name of the file and function containing the
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<B>assert</B>()
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call, the source code line number of the call, and the text of the argument;
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something like:
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<P>
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<BR> prog: some_file.c:16: some_func: Assertion `val == 0' failed.
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<P>
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If the macro
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<B>NDEBUG</B>
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is defined at the moment
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<I><<A HREF="file:///usr/include/assert.h">assert.h</A>></I>
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was last included, the macro
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<B>assert</B>()
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generates no code, and hence does nothing at all.
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It is not recommended to define
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<B>NDEBUG</B>
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if using
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<B>assert</B>()
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to detect error conditions since the software
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may behave non-deterministically.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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No value is returned.
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<A NAME="lbAF"> </A>
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<H2>ATTRIBUTES</H2>
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For an explanation of the terms used in this section, see
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<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
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<TABLE BORDER>
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<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>assert</B>()
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</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
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</TABLE>
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<P>
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<A NAME="lbAG"> </A>
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<H2>CONFORMING TO</H2>
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POSIX.1-2001, POSIX.1-2008, C89, C99.
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In C89,
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<I>expression</I>
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is required to be of type
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<I>int</I>
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and undefined behavior results if it is not, but in C99
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it may have any scalar type.
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<A NAME="lbAH"> </A>
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<H2>BUGS</H2>
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<B>assert</B>()
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is implemented as a macro; if the expression tested has side-effects,
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program behavior will be different depending on whether
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<B>NDEBUG</B>
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is defined.
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This may create Heisenbugs which go away when debugging
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is turned on.
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<A NAME="lbAI"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?3+abort">abort</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+assert_perror">assert_perror</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+exit">exit</A></B>(3)
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<A NAME="lbAJ"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="1"><A HREF="#lbAB">NAME</A><DD>
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<DT id="2"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="3"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="4"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="5"><A HREF="#lbAF">ATTRIBUTES</A><DD>
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<DT id="6"><A HREF="#lbAG">CONFORMING TO</A><DD>
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<DT id="7"><A HREF="#lbAH">BUGS</A><DD>
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<DT id="8"><A HREF="#lbAI">SEE ALSO</A><DD>
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<DT id="9"><A HREF="#lbAJ">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:35 GMT, March 31, 2021
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</BODY>
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</HTML>
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