[Bug libc/2449] New: adjtime() does not update oldelta if delta is NULL

["michael dot kerrisk at gmx dot net" <sourceware-bugzilla@sourceware.org>]

According to 'info adjtime', if the OLDDELTA argument is not a NULL 
pointer, then adjtime() returns information about any previous time
adjustment that has not yet completed.

However, this is only done if DELTA is non-NULL (i.e., we
are also changing the adjustment).  If we want to simply retrieve
the current delta without changing it (as the info man page implies
we can), then specifying 'DELTA' as NULL does not cause the 
remaining delta to be returned in OLDDELTA. 

I believe the problem actually lies in the kernel, where the
following patch should fix things:

--- time.c.orig	2006-03-12 11:03:10.000000000 +1300
+++ time.c	2006-03-12 11:04:26.000000000 +1300
@@ -375,7 +375,9 @@
 	    /* p. 24, (d) */
 		result = TIME_ERROR;
 	
-	if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
+	if(txc->modes == 0)
+	    txc->offset    = time_adjust;
+	else if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
 	    txc->offset	   = save_adjust;
 	else {
 	    txc->offset = shift_right(time_offset, SHIFT_UPDATE);

However, I submit this against glibc, because it is the (more portable)
glibc adjtime() interface that is (IMO) broken by this problem.  If you 
agree that this is the needed fix you can either push it to the 
kernel folk, or ask me to do so.

Cheers,

Michael

-- 
           Summary: adjtime() does not update oldelta if delta is NULL
           Product: glibc
           Version: 2.4
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: michael dot kerrisk at gmx dot net
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=2449

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