Improve boot-time gathering

Simplify Emacs proper by using Gnulib’s boot-time module
instead of doing it all by hand.  This should port Emacs
better to obscurish hosts, as Bruno Haible has merged the
best of Emacs’s and Gnulib’s boot-time gathering.
* lib/boot-time-aux.h, lib/boot-time.c, lib/boot-time.h:
* lib/readutmp.h, m4/readutmp.m4: New files, copied from Gnulib.
* admin/merge-gnulib (GNULIB_MODULES): Add boot-time.
* configure.ac: Do not check for utmp.h;
the boot-time module now does this.
(BOOT_TIME_FILE): Remove; no longer used.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* src/filelock.c [__FreeBSD__]: Do not include <sys/sysctl.h>.
[HAVE_UTMP_H]: Do not include utmp.h.
Include boot-time instead: boot-time does the work now.
(BOOT_TIME) [HAVE_ANDROID && !ANDROID_STUBIFY]: Don’t undef.
(WTMP_FILE): Don’t define.
(boot_time, boot_time_initialized, get_boot_time_1, get_boot_time):
Remove.
(get_boot_sec): New function that simply calls Gnulib get_boot_time.
(lock_file_1, current_lock_owner): Use get_boot_sec instead
of get_boot_time.

1 files changed, 10 insertions, 162 deletions

diff --git a/src/filelock.c b/src/filelock.c
index 3b1ff8ad566..d2161f1e58a 100644
--- a/src/filelock.c
+++ b/src/filelock.c
@@ -36,13 +36,9 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <sys/file.h>
 #include <fcntl.h>
 #include <unistd.h>
-
-#ifdef __FreeBSD__
-#include <sys/sysctl.h>
-#endif /* __FreeBSD__ */
-
 #include <errno.h>
 
+#include <boot-time.h>
 #include <c-ctype.h>
 
 #include "lisp.h"
@@ -55,20 +51,6 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #ifndef MSDOS
 
-#ifdef HAVE_UTMP_H
-#include <utmp.h>
-#endif
-
-/* Boot time is not available on Android.  */
-
-#if defined HAVE_ANDROID && !defined ANDROID_STUBIFY
-#undef BOOT_TIME
-#endif
-
-#if !defined WTMP_FILE && !defined WINDOWSNT && defined BOOT_TIME
-#define WTMP_FILE "/var/log/wtmp"
-#endif
-
 #ifdef HAVE_ANDROID
 #include "android.h" /* For `android_is_special_directory'.  */
 #endif /* HAVE_ANDROID */
@@ -127,153 +109,19 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 
 /* Return the time of the last system boot.  */
 
-static time_t boot_time;
-static bool boot_time_initialized;
-
-#ifdef BOOT_TIME
-static void get_boot_time_1 (const char *, bool);
-#endif
-
 static time_t
-get_boot_time (void)
+get_boot_sec (void)
 {
-  if (boot_time_initialized)
-    return boot_time;
-  boot_time_initialized = 1;
-
-#if defined (CTL_KERN) && defined (KERN_BOOTTIME)
-  {
-    int mib[2];
-    size_t size;
-    struct timeval boottime_val;
-
-    mib[0] = CTL_KERN;
-    mib[1] = KERN_BOOTTIME;
-    size = sizeof (boottime_val);
-
-    if (sysctl (mib, 2, &boottime_val, &size, NULL, 0) >= 0 && size != 0)
-      {
-        boot_time = boottime_val.tv_sec;
-        return boot_time;
-      }
-  }
-#endif /* defined (CTL_KERN) && defined (KERN_BOOTTIME) */
-
-#ifdef BOOT_TIME_FILE
-    {
-      struct stat st;
-      if (stat (BOOT_TIME_FILE, &st) == 0)
-        {
-          boot_time = st.st_mtime;
-          return boot_time;
-        }
-    }
-#endif /* BOOT_TIME_FILE */
-
-#if defined (BOOT_TIME)
-  /* The utmp routines maintain static state.  Don't touch that state
+  /* get_boot_time maintains static state.  Don't touch that state
      if we are going to dump, since it might not survive dumping.  */
   if (will_dump_p ())
-    return boot_time;
-
-  /* Try to get boot time from utmp before wtmp,
-     since utmp is typically much smaller than wtmp.
-     Passing a null pointer causes get_boot_time_1
-     to inspect the default file, namely utmp.  */
-  get_boot_time_1 (0, 0);
-  if (boot_time)
-    return boot_time;
-
-  /* Try to get boot time from the current wtmp file.  */
-  get_boot_time_1 (WTMP_FILE, 1);
-
-  /* If we did not find a boot time in wtmp, look at wtmp.1,
-     wtmp.1.gz, wtmp.2, wtmp.2.gz, and so on.  */
-  for (int counter = 0; counter < 20 && ! boot_time; counter++)
-    {
-      Lisp_Object filename = Qnil;
-      bool delete_flag = false;
-      char cmd_string[sizeof WTMP_FILE ".19.gz"];
-      AUTO_STRING_WITH_LEN (tempname, cmd_string,
-                            sprintf (cmd_string, "%s.%d", WTMP_FILE, counter));
-      if (! NILP (Ffile_exists_p (tempname)))
-        filename = tempname;
-      else
-        {
-          tempname = make_formatted_string (cmd_string, "%s.%d.gz",
-                                            WTMP_FILE, counter);
-          if (! NILP (Ffile_exists_p (tempname)))
-            {
-              /* The utmp functions on older systems accept only file
-                 names up to 8 bytes long.  Choose a 2 byte prefix, so
-                 the 6-byte suffix does not make the name too long.  */
-              filename = Fmake_temp_file_internal (build_string ("wt"), Qnil,
-                                                   empty_unibyte_string, Qnil);
-              CALLN (Fcall_process, build_string ("gzip"), Qnil,
-                     list2 (QCfile, filename), Qnil,
-                     build_string ("-cd"), tempname);
-              delete_flag = true;
-            }
-        }
-
-      if (! NILP (filename))
-        {
-          get_boot_time_1 (SSDATA (filename), 1);
-          if (delete_flag)
-            emacs_unlink (SSDATA (filename));
-        }
-    }
-
-  return boot_time;
-#else
-  return 0;
-#endif
-}
+    return 0;
 
-#ifdef BOOT_TIME
-/* Try to get the boot time from wtmp file FILENAME.
-   This succeeds if that file contains a reboot record.
-
-   If FILENAME is zero, use the same file as before;
-   if no FILENAME has ever been specified, this is the utmp file.
-   Use the newest reboot record if NEWEST,
-   the first reboot record otherwise.
-   Ignore all reboot records on or before BOOT_TIME.
-   Success is indicated by setting BOOT_TIME to a larger value.  */
-
-void
-get_boot_time_1 (const char *filename, bool newest)
-{
-  struct utmp ut, *utp;
-
-  if (filename)
-    utmpname (filename);
-
-  setutent ();
-
-  while (1)
-    {
-      /* Find the next reboot record.  */
-      ut.ut_type = BOOT_TIME;
-      utp = getutid (&ut);
-      if (! utp)
-        break;
-      /* Compare reboot times and use the newest one.  */
-      if (utp->ut_time > boot_time)
-        {
-          boot_time = utp->ut_time;
-          if (! newest)
-            break;
-        }
-      /* Advance on element in the file
-         so that getutid won't repeat the same one.  */
-      utp = getutent ();
-      if (! utp)
-        break;
-    }
-  endutent ();
+  struct timespec boot_time;
+  boot_time.tv_sec = 0;
+  get_boot_time (&boot_time);
+  return boot_time.tv_sec;
 }
-#endif /* BOOT_TIME */
 
 /* An arbitrary limit on lock contents length.  8 K should be plenty
    big enough in practice.  */
@@ -418,7 +266,7 @@ create_lock_file (char *lfname, char *lock_info_str, bool force)
 static int
 lock_file_1 (Lisp_Object lfname, bool force)
 {
-  intmax_t boot = get_boot_time ();
+  intmax_t boot = get_boot_sec ();
   Lisp_Object luser_name = Fuser_login_name (Qnil);
   Lisp_Object lhost_name = Fsystem_name ();
 
@@ -604,7 +452,7 @@ current_lock_owner (lock_info_type *owner, Lisp_Object lfname)
                && (kill (pid, 0) >= 0 || errno == EPERM)
                && (boot_time == 0
                    || (boot_time <= TYPE_MAXIMUM (time_t)
-                       && within_one_second (boot_time, get_boot_time ()))))
+                       && within_one_second (boot_time, get_boot_sec ()))))
         return ANOTHER_OWNS_IT;
       /* The owner process is dead or has a strange pid, so try to
          zap the lockfile.  */