assert(3) [freebsd man page]

ASSERT(3)						   BSD Library Functions Manual 						 ASSERT(3)

NAME

     assert -- expression verification macro

SYNOPSIS

     #include <assert.h>

     assert(expression);

DESCRIPTION

     The assert() macro tests the given expression and if it is false, the calling process is terminated.  A diagnostic message is written to
     stderr and the function abort(3) is called, effectively terminating the program.

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

     The assert() macro may be removed at compile time by defining NDEBUG as a macro (e.g., by using the cc(1) option -DNDEBUG).

EXAMPLES

     The assertion:

	   assert(1 == 0);

     generates a diagnostic message similar to the following:

	   Assertion failed: (1 == 0), function main, file assertion.c, line 100.

SEE ALSO

     abort(3)

STANDARDS

     The assert() macro conforms to ISO/IEC 9899:1999 (``ISO C99'').

HISTORY

     An assert macro appeared in Version 6 AT&T UNIX.

BSD
								 January 26, 1999							       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

       If the macro NDEBUG was defined at the moment <assert.h> was last included, the macro assert() generates no code, and hence does nothing at
       all.  Otherwise, the macro assert() prints an error message to standard output and terminates the program by calling abort() if	expression
       is false (i.e., compares equal to zero).

       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.

RETURN VALUE

       No value is returned.

CONFORMING TO

       ISO9899 (ANSI C).  In the 1990 standard, expression is required to be of type int and undefined behavior results if it is not, but  in  the
       1999 standard it may have any scalar type.

BUGS

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

SEE ALSO

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

C99								    2002-08-25								 ASSERT(3)