migration: use GDateTime for formatting timestamp in snapshot names

The GDateTime APIs provided by GLib avoid portability pitfalls, such
as some platforms where 'struct timeval.tv_sec' field is still 'long'
instead of 'time_t'. When combined with automatic cleanup, GDateTime
often results in simpler code too.

Reviewed-by: Dr. David Alan Gilbert <[email protected]>
Signed-off-by: Daniel P. Berrangé <[email protected]>

Author: berrange

migration/savevm.c

@@ -2775,8 +2775,7 @@ bool save_snapshot(const char *name, bool overwrite, const char *vmstate,
     QEMUFile *f;
     int saved_vm_running;
     uint64_t vm_state_size;
-    qemu_timeval tv;
-    struct tm tm;
+    g_autoptr(GDateTime) now = g_date_time_new_now_local();
     AioContext *aio_context;
 
     if (migration_is_blocked(errp)) {
@@ -2836,9 +2835,8 @@ bool save_snapshot(const char *name, bool overwrite, const char *vmstate,
     memset(sn, 0, sizeof(*sn));
 
     /* fill auxiliary fields */
-    qemu_gettimeofday(&tv);
-    sn->date_sec = tv.tv_sec;
-    sn->date_nsec = tv.tv_usec * 1000;
+    sn->date_sec = g_date_time_to_unix(now);
+    sn->date_nsec = g_date_time_get_microsecond(now) * 1000;
     sn->vm_clock_nsec = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     if (replay_mode != REPLAY_MODE_NONE) {
         sn->icount = replay_get_current_icount();
@@ -2849,9 +2847,8 @@ bool save_snapshot(const char *name, bool overwrite, const char *vmstate,
     if (name) {
         pstrcpy(sn->name, sizeof(sn->name), name);
     } else {
-        /* cast below needed for OpenBSD where tv_sec is still 'long' */
-        localtime_r((const time_t *)&tv.tv_sec, &tm);
-        strftime(sn->name, sizeof(sn->name), "vm-%Y%m%d%H%M%S", &tm);
+        g_autofree char *autoname = g_date_time_format(now,  "vm-%Y%m%d%H%M%S");
+        pstrcpy(sn->name, sizeof(sn->name), autoname);
     }
 
     /* save the VM state */