time_t definition

[Lowell Gilbert]

Polytropon <freebsd at edvax.de> writes:

> On Wed, 16 Jan 2013 10:21:03 -0800, Michael Sierchio wrote:
>> Top posting for brevity - the fact is, the code in your original
>> example is wrong.  There are reasons to complain about argument size
>> mismatches, esp. in print functions that call (versions of) malloc.
>> You should cast the time_t value explicitly, or use %d instead of %ld.
>
> This advice looks correct. If you use the source Luke,
> you'll find the following (taken from a 8.2-STABLE/i386
> system source tree):
>
> /usr/src/sys/sys/types.h (line 253):
>
> 	typedef __time_t time_t;
>
> /usr/src/sys/i386/include/_types.h (line 97):
>
> 	typedef __int32_t __time_t;
>
> /usr/src/sys/i386/include/_types.h (line 55):
>
> 	typedef int __int32_t;
>
> So it boils down to (int), but %ld expects (long). This
> is the exact content of the warning. You can either
> case the (time_t) value to (long), or change %ld to %d
> to avoid the warning.

Even if the representations boil down to the same thing, the cast is
still a good idea. You may *know* (for example) that time_t is really an
int, but you don't know that it always will be. printf() (like other
variadic functions) loses type information, so make *sure* you cast the
type to what the format says it is, because the Usual Arithmetic
Conversions cannot come in to save your bacon if (when) you're wrong.