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 standard output and terminates the program by calling abort() 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.
assert() is implemented as a macro; if the expression tested has
side-effects, program behaviour will be different depending on whether
NDEBUG is defined. This may create Heisenbugs which go away when
debugging is turned on.