_diagassert(3) [netbsd man page]

_DIAGASSERT(3)						   BSD Library Functions Manual 					    _DIAGASSERT(3)

NAME

     _DIAGASSERT -- expression verification macro

SYNOPSIS

     #include <assert.h>

     _DIAGASSERT(expression);

DESCRIPTION

     The _DIAGASSERT() macro tests the given expression and if it is false, one or more of the following may occur:

	   o   a diagnostic message may be logged to the system logger with syslog(3).	This is default behaviour.

	   o   a diagnostic message may be printed to the stderr stream.

	   o   the calling process will be terminated by calling abort(3).

     This behaviour may be changed by setting the LIBC_DIAGASSERT environment variable (see below).

     The diagnostic message consists of the text of the expression, the name of the source file, the line number and the enclosing function.

     If expression is true, the _DIAGASSERT() macro does nothing.

     The _DIAGASSERT() macro is not compiled in by default, and will only be compiled in with the cc(1) option -D_DIAGNOSTIC.

     This macro is used in the various system libraries such as the Standard C Library (libc, -lc) to ensure that various library calls are
     invoked with valid arguments.

ENVIRONMENT

     The LIBC_DIAGASSERT environment variable can be used to modify the default behaviour of logging the assertion to the system logger.

     LIBC_DIAGASSERT may be set to one or more of the following characters:

	   a	abort(3) once any assertion messages have been logged and/or printed.

	   A	Opposite of ``a''.

	   e	Print the assertion message to the stderr stream.

	   E	Opposite of ``e''.

	   l	Log the assertion message with syslog(3) to the facility user.debug.

	   L	Opposite of ``l''.

DIAGNOSTICS

     The diagnostic message has the following format:

	   "assertion "%s" failed: file "%s", line %d, function "%s"
",
		       "expression", __FILE__, __LINE__, __func__

SEE ALSO

     cc(1), abort(3), assert(3), syslog(3)

HISTORY

     The _DIAGASSERT macro appeared in NetBSD 1.5.

BSD
								 January 22, 2007							       BSD

ASSERT(3)						     Linux Programmer's Manual							 ASSERT(3)

NAME

       assert - abort the program if assertion is false

SYNOPSIS

       #include <assert.h>

       void assert(scalar expression);

DESCRIPTION

       This  macro  can  help programmers find bugs in their programs, or handle exceptional cases via a crash that will produce limited debugging
       output.

       If expression is false (i.e., compares equal to zero), assert() prints an error message to standard error and  terminates  the  program	by
       calling	abort(3).   The error message includes the name of the file and function containing the assert() call, the source code line number
       of the call, and the text of the argument; something like:

	   prog: some_file.c:16: some_func: Assertion `val == 0' failed.

       If the macro NDEBUG is defined at the moment <assert.h> was last included, the macro assert() generates no code, and hence does nothing	at
       all.   It  is not recommended to define NDEBUG if using assert() to detect error conditions since the software may behave non-deterministi-
       cally.

RETURN VALUE

       No value is returned.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       +----------+---------------+---------+
       |Interface | Attribute	  | Value   |
       +----------+---------------+---------+
       |assert()  | Thread safety | MT-Safe |
       +----------+---------------+---------+

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008, C89, C99.  In C89, expression is required to be of type int and undefined behavior results if it is not, but in
       C99 it may have any scalar type.

BUGS

       assert() is implemented as a macro; if the expression tested has side-effects, program behavior will be different depending on whether NDE-
       BUG is defined.	This may create Heisenbugs which go away when debugging is turned on.

SEE ALSO

       abort(3), assert_perror(3), exit(3)

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

GNU
								    2017-09-15								 ASSERT(3)