Re: [9fans] off topic - a good Git reference

[Charles Forsyth <charles.forsyth@gmail.com>]

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On 30 September 2015 at 08:47, Charles Forsyth <charles.forsyth@gmail.com>
wrote:

> I was being sarcastic about the portability of so much contemporary C code.


Here's a small but representative example.

#if HAVE_SYS_TIME_H
#include <sys/time.h
#elif HAVE_TIME_H
#include <time.h>
#endif

#if HAVE_SYS_CLOCK_GETTIME
time_t
time_now(void)
{
  struct timespec timespec_value;
  (void) clock_gettime(CLOCK_REALTIME, &timespec_value);
  return timespec_value.tv_seconds;
}
#elif HAVE_SYS_GETTIMEOFDAY
time_t
time_now(void)
{
  struct timeval timeval_value;
  (void) gettimeofday(&timeval_value, (struct timezone *) NULL);
  return timeval_value.tv_seconds;
}
#elif HAVE_SYS_TIME
time_t
time_now(void)
{
  time_t seconds_since_epoch;
  (void) time(&seconds_since_epoch);
  return seconds_since_epoch;
}
#endif

./configure    # work out which HAVE_... definitions to use

Usually there are a few more alternatives enumerated.  Surprisingly often,
the microseconds or nanoseconds
value is discarded, to get the seconds. You could just use #include
<time.h> and call time(NULL) to get that, but where's the fun?

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