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 error 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.
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 behaviour will be different depending on whether
NDEBUG is defined. This may create Heisenbugs which go away when debugging
is turned on.
