First proposal for new ISO C 9x time API

Joseph S. Myers jsm28 at
Sat Sep 5 22:51:55 UTC 1998

On Sat, 5 Sep 1998, Paul Eggert wrote:

>    > It would be a good idea to use a common prefix for the structure elemen=
>    ts
>    > (xtm_nsec, xtm_sec, etc.).
>    I never understood what these common prefixes are good for.
> I believe that they were put in for historical reasons.  In very old
> versions of the C compiler, all structure members lived in the same
> name space.  Nowadays this original motivation is not important, but
> the tradition lives on in some places.  Personally, I don't think the
> xtm_ is needed, but I don't care too much one way or the other.

There's still the interaction with the macro namespace (user macros named
sec, etc.) - with a common prefix the standard could follow POSIX.1 and
say that any name beginning xtm_ must not be declared or #defined by the
application if <xtime.h> is included - which could help extensibility.
(There's a discussion of structure extensibility and user macros in the
POSIX.1 rationale - see B.2.7.2.)

Joseph S. Myers
jsm28 at

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