assert – abort the program if assertion is false

USAGE
       #include <assert.h>

       void assert(scalar expression);

DESCRIPTION
       If  the  macro  NDEBUG  was  defined  at the moment  was last
       included, the macro assert() generates no code, and hence does  nothing
       at all.  Otherwise, the macro assert() prints an error message to stan-
       dard error 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
       POSIX.1-2001,  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 behaviour will be different depending on whether  NDE-
       BUG  is  defined.  This may create Heisenbugs which go away when debug-
       ging is turned on.

SEE ALSO
       abort(3), assert_perror(3), exit(3)