* Alejandro Colomar <alx.manpa...@gmail.com>, 2022-07-24, 21:19:
+.B "#define NULL ((void *) 0)" +.fi +.SH DESCRIPTION +.B NULL +represents a null pointer constant. +.PP +According to POSIX, +it shall expand to an integer constant expression with the value +.B 0 +cast to type +.IR "void *" .
Might be worth noting that the cast requirement was added only in POSIX.1-2008 aka SUSv4.
+.SH CONFORMING TO +C99 and later;
It's in C89 too.
+.I NULL \- NULL +is, surprisingly, undefined behavior, according to ISO C.
FWIW, I don't find it surprising at all. -- Jakub Wilk
