I wrote:
> Interesting question, so I took a look:
> https://git.musl-libc.org/cgit/musl/tree/src/stdio/vfprintf.c#n593
> case 's':
> a = arg.p ? arg.p : "(null)";
BTW, the adjacent code shows that musl is also supporting glibc's
"%m" extension, so I imagine that they are endeavoring to be
compatible with glibc, and this goes along with that. But that
just supports my larger point: printing "(null)" is clearly the
de facto standard now, whether or not POSIX has caught up with it.
regards, tom lane