mirror of https://github.com/mkerrisk/man-pages
109 lines
3.2 KiB
Groff
109 lines
3.2 KiB
Groff
.\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" Modified Sat Jul 24 21:42:42 1993 by Rik Faith <faith@cs.unc.edu>
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.\" Modified Tue Oct 22 23:44:11 1996 by Eric S. Raymond <esr@thyrsus.com>
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.\" Modified Thu Jun 2 23:44:11 2016 by Nikos Mavrogiannopoulos <nmav@redhat.com>
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.TH ASSERT 3 2017-09-15 "GNU" "Linux Programmer's Manual"
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.SH NAME
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assert \- abort the program if assertion is false
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.SH SYNOPSIS
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.nf
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.B #include <assert.h>
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.PP
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.BI "void assert(scalar " expression );
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.fi
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.SH DESCRIPTION
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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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.PP
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If
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.I expression
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is false (i.e., compares equal to zero),
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.BR assert ()
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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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.BR abort (3).
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The error message includes the name of the file and function containing the
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.BR assert ()
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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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.PP
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.in +4n
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.EX
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prog: some_file.c:16: some_func: Assertion \`val == 0\(aq failed.
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.EE
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.in
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.PP
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If the macro
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.B NDEBUG
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is defined at the moment
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.I <assert.h>
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was last included, the macro
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.BR assert ()
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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
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if using
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.BR assert ()
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to detect error conditions since the software
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may behave non-deterministically.
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.SH RETURN VALUE
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No value is returned.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lb lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR assert ()
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T} Thread safety MT-Safe
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.TE
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.sp 1
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.SH CONFORMING TO
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POSIX.1-2001, POSIX.1-2008, C89, C99.
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In C89,
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.I expression
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is required to be of type
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.I int
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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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.\" See Defect Report 107 for more details.
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.SH BUGS
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.BR assert ()
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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
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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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.SH SEE ALSO
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.BR abort (3),
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.BR assert_perror (3),
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.BR exit (3)
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