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 If the macro NDEBUG was defined at the moment <assert.h> 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(3) 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 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 3.22 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at

GNU 2002-08-25 ASSERT(3)