assert(3) [x11r4 man page]

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)

ASSERT(3P)						     POSIX Programmer's Manual							ASSERT(3P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

       assert - insert program diagnostics

SYNOPSIS

       #include <assert.h>

       void assert(scalar expression);

DESCRIPTION

       The assert() macro shall insert diagnostics into programs; it shall expand to a void expression. When it is executed, if expression  (which
       shall  have  a scalar type) is false (that is, compares equal to 0), assert() shall write information about the particular call that failed
       on stderr and shall call abort().

       The information written about the call that failed shall include the text of the argument, the name of the source  file,  the  source  file
       line  number,  and  the	name  of the enclosing function; the latter are, respectively, the values of the preprocessing macros __FILE__ and
       __LINE__ and of the identifier __func__.

       Forcing a definition of the name NDEBUG, either from the compiler command line or with the preprocessor control	statement  #define  NDEBUG
       ahead of the #include <assert.h> statement, shall stop assertions from being compiled into the program.

RETURN VALUE

       The assert() macro shall not return a value.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       abort(), stderr, the Base Definitions volume of IEEE Std 1003.1-2001, <assert.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical  and	Electronics  Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE
       and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can  be  obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								ASSERT(3P)