[LEAPSECS] Lets get REAL about time.

[Paul J. Ste. Marie]

On 1/22/2012 7:42 AM,  Clive D.W. Feather wrote:

> #define timespecsub(vvp, uvp)            \

>      ((vvp)->tv_sec -= (uvp)->tv_sec,     \

>       (vvp)->tv_nsec -= (uvp)->tv_nsec,   \

>       ((vvp)->tv_nsec<  0)                \

>        ? ((vvp)->tv_sec--, (vvp)->tv_nsec += 1000000000) \

>        : (void) 0)

>

> This has the advantage of being usable wherever a function can appear.


Not really.  For example &timespecsub doesn't work.  The do-while kludge 
can at least protect the arguments, eg:

#define timespecsub(vvp1, uvp1)                                 \
	do {                                                    \
		const struct timespec *vvp = vvp1;		\
		const struct timespec *uvp = uvp1;		\
		(vvp)->tv_sec -= (uvp)->tv_sec;                 \
		(vvp)->tv_sec -= (uvp)->tv_sec;                 \
		(vvp)->tv_sec -= (uvp)->tv_sec;                 \
		(vvp)->tv_nsec -= (uvp)->tv_nsec;               \
		if ((vvp)->tv_nsec < 0) {                       \
			(vvp)->tv_sec--;                        \
			(vvp)->tv_nsec += 1000000000;           \
		}                                               \
	} while (0)

and aside from not having an address otherwise behaves like a void function.

-- 
         --Paul