3 files changed, 52 insertions, 58 deletions
diff --git a/manual/examples/strftim.c b/manual/examples/strftim.c
index 304981d..6e1e047 100644
--- a/manual/examples/strftim.c
+++ b/manual/examples/strftim.c
@@ -18,30 +18,32 @@
 #include <time.h>
 #include <stdio.h>
 
-#define SIZE 256
-
 int
 main (void)
 {
-  char buffer[SIZE];
-  time_t curtime;
-  struct tm *loctime;
+  /* This buffer is big enough that the strftime calls
+     below cannot possibly exhaust it.  */
+  char buf[256];
 
   /* Get the current time. */
-  curtime = time (NULL);
+  time_t curtime = time (NULL);
 
   /* Convert it to local time representation. */
-  loctime = localtime (&curtime);
+  struct tm *lt = localtime (&curtime);
+  if (!lt)
+    return 1;
 
-  /* Print out the date and time in the standard format. */
-  fputs (asctime (loctime), stdout);
+  /* Print the date and time in a simple format
+     that is independent of locale. */
+  strftime (buf, sizeof buf, "%Y-%m-%d %H:%M:%S", lt);
+  puts (buf);
 
 /*@group*/
-  /* Print it out in a nice format. */
-  strftime (buffer, SIZE, "Today is %A, %B %d.\n", loctime);
-  fputs (buffer, stdout);
-  strftime (buffer, SIZE, "The time is %I:%M %p.\n", loctime);
-  fputs (buffer, stdout);
+  /* Print it in a nicer English format. */
+  strftime (buf, sizeof buf, "Today is %A, %B %d.", lt);
+  puts (buf);
+  strftime (buf, sizeof buf, "The time is %I:%M %p.", lt);
+  puts (buf);
 
   return 0;
 }
diff --git a/manual/examples/timespec_subtract.c b/manual/examples/timespec_subtract.c
new file mode 100644
index 0000000..380d173
--- /dev/null
+++ b/manual/examples/timespec_subtract.c
@@ -0,0 +1,36 @@
+/* struct timespec subtraction.
+   Copyright (C) 1991-2024 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <https://www.gnu.org/licenses/>.
+*/
+#include <stdckdint.h>
+#include <time.h>
+
+/* Put into *R the difference between X and Y.
+   Return true if overflow occurs, false otherwise.  */
+
+bool
+timespec_subtract (struct timespec *r,
+		   struct timespec x, struct timespec y)
+{
+  /* Compute nanoseconds, setting @var{borrow} to 1, 0, or -1
+     for propagation into seconds.  */
+  long int nsec_diff = x.tv_nsec - y.tv_nsec;
+  int borrow = (nsec_diff < 0) - ! (nsec_diff < 1000000000);
+  r->tv_nsec = nsec_diff + 1000000000 * borrow;
+
+  /* Compute seconds, returning true if this overflows.  */
+  bool v = ckd_sub (&r->tv_sec, x.tv_sec, y.tv_sec);
+  return v ^ ckd_sub (&r->tv_sec, r->tv_sec, borrow);
+}
diff --git a/manual/examples/timeval_subtract.c b/manual/examples/timeval_subtract.c
deleted file mode 100644
index 20c2463..0000000
--- a/manual/examples/timeval_subtract.c
+++ /dev/null
@@ -1,44 +0,0 @@
-/* struct timeval subtraction.
-   Copyright (C) 1991-2024 Free Software Foundation, Inc.
-
-   This program is free software; you can redistribute it and/or
-   modify it under the terms of the GNU General Public License
-   as published by the Free Software Foundation; either version 2
-   of the License, or (at your option) any later version.
-
-   This program is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-   GNU General Public License for more details.
-
-   You should have received a copy of the GNU General Public License
-   along with this program; if not, see <https://www.gnu.org/licenses/>.
-*/
-
-/* Subtract the `struct timeval' values X and Y,
-   storing the result in RESULT.
-   Return 1 if the difference is negative, otherwise 0.  */
-
-int
-timeval_subtract (struct timeval *result, struct timeval *x, struct timeval *y)
-{
-  /* Perform the carry for the later subtraction by updating @var{y}. */
-  if (x->tv_usec < y->tv_usec) {
-    int nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1;
-    y->tv_usec -= 1000000 * nsec;
-    y->tv_sec += nsec;
-  }
-  if (x->tv_usec - y->tv_usec > 1000000) {
-    int nsec = (x->tv_usec - y->tv_usec) / 1000000;
-    y->tv_usec += 1000000 * nsec;
-    y->tv_sec -= nsec;
-  }
-
-  /* Compute the time remaining to wait.
-     @code{tv_usec} is certainly positive. */
-  result->tv_sec = x->tv_sec - y->tv_sec;
-  result->tv_usec = x->tv_usec - y->tv_usec;
-
-  /* Return 1 if result is negative. */
-  return x->tv_sec < y->tv_sec;
-}