Linux Programmer’s Manual
assert − abort the program if assertion is false
void assert(scalar expression);
If the macro NDEBUG was defined at the moment <assert.h> was last included, the macro assert() gener-
ates 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
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.
No value is returned.
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.
assert() is implemented as a macro; if the expression tested has side-effects, program behavior will be dif-
ferent 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)
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