[RFC PATCH 51/52] Y2038: add RPC functions

[Paul Eggert]

Paul Eggert wrote:
> 
>    /* time_t is always 'long int' in the GNU C Library.  */
>    #define TIME_T_MIN LONG_MIN
>    #define TIME_T_MAX LONG_MAX
> 
>    static inline bool
>    fits_in_time_t (__time64_t t)
>    {
>    #if 7 <= __GNUC__
>      return !__builtin_add_overflow_p (t, 0, TIME_T_MAX);
>    #endif
>      return TIME_T_MIN <= t && t <= TIME_T_MAX;
>    }

Marc Glisse suggested a simpler solution:

   static inline bool
   fits_in_time_t (__time64_t t)
   {
     return t == (time64_t) t;
   }

This is documented to work for GCC, something I had forgotten, and it generates 
better code for pre-7 GCC. See:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82170#c2