Am Di., 6. Apr. 2021 um 23:04 Uhr schrieb Bruno Haible <bruno@clisp.org>:

> > > But when designing a general utility, for all kinds of programs to use,
> > > it is inappropriate to say "storing null elements is not useful".
> >
> > I'm afraid we'll have to disagree here.
>
> In some of my uses of the gl_list module, the element is in fact a small
> integer, cast to an 'uintptr_t' and then further cast to a 'const void *'.
> If the API would forbid storing a NULL pointer, my specialized container
> type would need a workaround for storing the integer value 0.
>

NULL can also be a sensible value for "holes" in the list showing up in
algorithms that need to lazily remove elements (e.g. the list will only be
eventually compactified).