Introduction and 64 bit time_t

[Philipp.Trommler@preh.de]

Am Mittwoch, den 09.08.2017, 14:35 +0200 schrieb Corinna Vinschen:

[snip]

> I'd prefer to use the type long on LP64 systems, but long long should
> work fine for all 32 bit systems (baring 32 bit Cygwin).
> 
> However, a developer might want to design an embedded system still
> using
> a 32 bit time_t for the time being, so there should be some build-
> time
> switch for this case.  We're talking about a 21 year timeframe, which
> may still be more than enough for some systems.

So we can agree on a build-time switch like --enable-long-long-time-t
which defaults to off? That way the compilation of newlib itself could
be handled easily, but for the compilation of applications using time_t
I'm facing (at least) two possible implementations:

1. Having the user define something before including time.h in order to
   select the non-default long long, e.g.

      #define _USE_LONG_LONG_TIME_T
      #include <time.h>

2. Rewriting either time.h or sys/types.h at build-time depending on
   the configure switch to define this value or, even simpler, rewrite
   the definition of _TIME_T_ at build-time.

Am I correct here and which of these implementations would you prefer?
Or am I missing something completely here?

Regards
Philipp