fopen + mmap

[Roland McGrath]

> Neither C99 nor POSIX.1-2001 defines fflush on input streams, or on update
> streams where the last operation was input.  SUS2 doesn't either.

Ah, I see.  They changed the story in the past year and broke strictly
conforming POSIX.1-1996 applications.  So what you are saying is that we
need to have stdio behave differently depending on the _POSIX_C_SOURCE
value defined by the user to both be compatible with strictly conforming
POSIX.1-1996 applications, and to have different behavior that is
sufficient for strictly conforming POSIX.1-2001 applications.