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Re: [libvirt] [PATCH] Pass a correct pointer type to localtime_r(3).

From: Paul Eggert
Subject: Re: [libvirt] [PATCH] Pass a correct pointer type to localtime_r(3).
Date: Tue, 04 Sep 2012 10:03:41 -0700
User-agent: Mozilla/5.0 (X11; Linux i686; rv:15.0) Gecko/20120827 Thunderbird/15.0

On 09/04/2012 08:20 AM, Eric Blake wrote:
> tv_sec is required by POSIX to be
> of type time_t; so this is a bug in the OpenBSD header

Most likely this problem arose because of the patch I pushed
in gnulib commit e07d7c40f3ca5ec410cf5aa6fa03cfe51e712039.
Previously, gnulib required timeval's tv_sec to be
the same size as time_t.  But now, it requires only that
tv_sec be big enough to hold a time_t.

This patch was needed for Emacs.  Without the patch, gnulib
replaced struct timeval on OpenBSD, and this messed up
utimens.c, and Emacs wouldn't build.

Alternatively, gnulib could substitute its own struct timeval
for the system's, wrapping every struct timeval-using function
(gettimeofday, futimesat, futimes, lutimes, etc.  That'd be
more work, though.  And it would introduce some performance
issues with gettimeofday, which is supposed to be fast.

I've been trying to get away from using struct timeval,
and to use the higher-resolution struct timespec instead,
so messing with these obsolescent interfaces has been
lower priority for me.  But if someone wants to take the
more-ambitious approach that'd be fine, I expect.

For this particular case, though, how about if we avoid
the problem entirely?  libvirt doesn't need to use struct
timeval here at all.  I'd use the following (untested) patch:
it makes libvirt smaller and probably faster, and it ports
to OpenBSD without messing with gnulib:

diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
index f0ec742..3cef782 100644
--- a/tools/virsh-domain.c
+++ b/tools/virsh-domain.c
@@ -3707,7 +3707,7 @@ static char *
 vshGenFileName(vshControl *ctl, virDomainPtr dom, const char *mime)
     char timestr[100];
-    struct timeval cur_time;
+    time_t cur_time;
     struct tm time_info;
     const char *ext = NULL;
     char *ret = NULL;
@@ -3723,8 +3723,8 @@ vshGenFileName(vshControl *ctl, virDomainPtr dom, const 
char *mime)
         ext = ".png";
     /* add mime type here */
-    gettimeofday(&cur_time, NULL);
-    localtime_r(&cur_time.tv_sec, &time_info);
+    time (&cur_time);
+    localtime_r(&cur_time, &time_info);
     strftime(timestr, sizeof(timestr), "%Y-%m-%d-%H:%M:%S", &time_info);
     if (virAsprintf(&ret, "%s-%s%s", virDomainGetName(dom),
diff --git a/tools/virsh.c b/tools/virsh.c
index 5cf3237..88da429 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -2187,7 +2187,7 @@ vshOutputLogFile(vshControl *ctl, int log_level, const 
char *msg_format,
     char *str;
     size_t len;
     const char *lvl = "";
-    struct timeval stTimeval;
+    time_t stTime;
     struct tm *stTm;
     if (ctl->log_fd == -1)
@@ -2198,8 +2198,8 @@ vshOutputLogFile(vshControl *ctl, int log_level, const 
char *msg_format,
-    gettimeofday(&stTimeval, NULL);
-    stTm = localtime(&stTimeval.tv_sec);
+    time (&stTime);
+    stTm = localtime(&stTime);
     virBufferAsprintf(&buf, "[%d.%02d.%02d %02d:%02d:%02d %s %d] ",
                       (1900 + stTm->tm_year),
                       (1 + stTm->tm_mon),

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