NAME

       assert - abort the program if assertion is false

LIBRARY

       Standard C library (libc, -lc)

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-deterministically.

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 │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       C89, C99, POSIX.1-2001.

       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  NDEBUG  is  defined.   This  may  create
       Heisenbugs which go away when debugging is turned on.

SEE ALSO

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