Query about multiple inclusion of a header

[Moderator, John S. Quarterman]

From: Andy Tanenbaum <uunet!cs.vu.nl!ast>

The ANSI C standard specifically states that it is legal for an
application program to include the ANSI headers (e.g., <limits.h>)
multiple times in a program.

What about the POSIX headers that are not in the ANSI std, such as
<unistd.h> and <sys/wait.h>.  Is an implementation required to behave
correctly if they are included multiple times?  If so, could somebody
point out the section in P1003.1 where this is stated.

Thanks.

Andy Tanenbaum (ast at cs.vu.nl)

Volume-Number: Volume 17, Number 64