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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 recom‐
       mended 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)

GNU                                                                            2021-03-22                                                                      ASSERT(3)