assert(3)                                             Library Functions Manual                                            assert(3)

       assert - abort the program if assertion is false

       Standard C library (libc, -lc)

       #include <assert.h>

       void assert(scalar expression);

       This  macro can help programmers find bugs in their programs, or handle exceptional cases via a crash that will produce lim‐
       ited 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.

       No value is returned.

       For an explanation of the terms used in this section, see attributes(7).

       │Interface                                                                                        │ Attribute     │ Value   │
       │assert()                                                                                         │ Thread safety │ MT-Safe │

       POSIX.1-2001, POSIX.1-2008, C99.

       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.

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

Linux man-pages 6.03                                         2023-02-05                                                   assert(3)