| .\" (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de) |
| .\" |
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| .\" manual under the conditions for verbatim copying, provided that the |
| .\" entire resulting derived work is distributed under the terms of a |
| .\" permission notice identical to this one. |
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| .\" Since the Linux kernel and libraries are constantly changing, this |
| .\" manual page may be incorrect or out-of-date. The author(s) assume no |
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| .\" Modified Sat Jul 24 21:42:42 1993 by Rik Faith <faith@cs.unc.edu> |
| .\" Modified Tue Oct 22 23:44:11 1996 by Eric S. Raymond <esr@thyrsus.com> |
| .TH ASSERT 3 2002-08-25 "C99" "Linux Programmer's Manual" |
| .SH NAME |
| assert \- abort the program if assertion is false |
| .SH SYNOPSIS |
| .nf |
| .B #include <assert.h> |
| .sp |
| .BI "void assert(scalar " expression ); |
| .fi |
| .SH DESCRIPTION |
| If the macro |
| .B NDEBUG |
| was defined at the moment |
| .I <assert.h> |
| was last included, the macro |
| .BR assert () |
| generates no code, and hence does nothing at all. |
| Otherwise, the macro |
| .BR assert () |
| prints an error message to standard error and terminates the program |
| by calling |
| .BR abort () |
| if |
| .I expression |
| is false (i.e., compares equal to zero). |
| .LP |
| The purpose of this macro is to help the programmer find bugs in |
| his program. The message "assertion failed in file foo.c, function |
| do_bar(), line 1287" is of no help at all to a user. |
| .SH "RETURN VALUE" |
| No value is returned. |
| .SH "CONFORMING TO" |
| ISO9899 (ANSI C). In the 1990 standard, |
| .I expression |
| is required to be of type |
| .B int |
| and undefined behavior results if it is not, but in the 1999 standard |
| it may have any scalar type. |
| .\" See Defect Report 107 for more details. |
| .SH BUGS |
| .BR assert () |
| is implemented as a macro; if the expression tested has side-effects, |
| program behaviour will be different depending on whether |
| .B NDEBUG |
| is defined. This may create Heisenbugs which go away when debugging |
| is turned on. |
| .SH "SEE ALSO" |
| .BR abort (3), |
| .BR assert_perror (3), |
| .BR exit (3) |