Bug#762677: libc0.3: Hurd futimens does not support UTIME_NOW

[Colin Watson <cjwatson@debian.org>]

Package: libc0.3
Version: 2.19-11
Severity: normal

The futimens patch for the Hurd does not support UTIME_NOW or
UTIME_OMIT.  POSIX says:

  "If the tv_nsec field of a timespec structure has the special value
  UTIME_NOW, the file's relevant timestamp shall be set to the greatest
  value supported by the file system that is not greater than the
  current time.  If the tv_nsec field has the special value UTIME_OMIT,
  the file's relevant timestamp shall not be changed.  In either case,
  the tv_sec field shall be ignored."

This is the cause of the current man-db build failure:

  https://buildd.debian.org/status/fetch.php?pkg=man-db&arch=hurd-i386&ver=2.7.0.1-1&stamp=1411530073

Gnulib defines UTIME_NOW to (-1) if it is not defined by the system.
But, since futimens doesn't specifically support it, setting the mtime
to {0, UTIME_NOW} just results in a timestamp one nanosecond less than
the epoch, which is not very useful.  The attached test program, when
run with a file name argument, should result in a file whose
modification time is set to the current time.

I'll see if I can modify Gnulib or failing that man-db to work around
this, but of course it would be better for futimens to be fixed.

Thanks,

-- 
Colin Watson                                       [cjwatson@debian.org]

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define MUST(name, cond) \
	do { \
		if (!(cond)) { \
			fprintf (stderr, name " failed\n"); \
			abort (); \
		} \
	} while (0)

int main (int argc, char **argv)
{
	int fd;
	struct timespec times[2];

	if (argc < 2) {
		fprintf (stderr, "need file name\n");
		exit (2);
	}
	fd = open (argv[1], O_RDWR | O_CREAT | O_TRUNC, 0666);
	MUST ("open", fd >= 0);
	times[0].tv_sec = 0;
	times[0].tv_nsec = UTIME_NOW;
	times[1].tv_sec = 0;
	times[1].tv_nsec = UTIME_NOW;
	MUST ("futimens", futimens (fd, times) == 0);
	MUST ("close", close (fd) == 0);
	return 0;
}