Re: [PATCH v5 1/2] Y2038: Add 64-bit time for all architectures

[Albert ARIBAUD <albert.aribaud@3adev.fr>]

On Wed, 20 Jun 2018 08:04:27 +0200, Albert ARIBAUD
<albert.aribaud@3adev.fr> wrote :

> But we can do something that keeps the code explicit /and/ reduces
> it properly, based on the fact that we always call fits_in_time_t() to
> perform a cast to time_t or set errno and reduce to -1 if we cannot
> cast.
> 
> We could put the consequence with the test, and instead of defining
> fits_in_time_t(), we could define reduce_to_time_t() as follows:
> 
> 	/* Check whether a time64_t value fits in a time_t.  */
> 	static inline time_t
> 	reduce_to_time_t (__time64_t t)
> 	{
> 	  if (t == (time_t) t)
> 	    return t;
> 	  __set_errno (EOVERFLOW);
> 	  return -1;
> 	}
> 

Trying to define the function above in include/time.h fails because
include/time.h needs to include include/errno.h to get the definition
of __set_errno, but both header files include each other, and some
C files include errno.h alone (or first), which results in the
preprocessor meeting the definition of reduce_to_time_t() before that
of __set_errno and rightly complaining that (function) __set_errno has
not been declared yet.

There is no easy way out of this, since the definition of __set_errno
requires that of errno, which in turn requires tls.h.

Or am I missing something?

Cordialement,
Albert ARIBAUD
3ADEV