assert

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

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 NDEBUG
       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 5.13 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                                2021-03-22                          ASSERT(3)