Re: Emacs current-time-string core dump on 64-bit hosts

[Paul Eggert]

Richard Stallman <rms@gnu.org> writes:

> Ok, you can install this change.
>
> However, we don't want any of these changes to be operative on the GNU
> system because all they do is cause trouble.  On the GNU system, large
> year numbers work.  Why interfere with their use?
>
> So I think you should conditionalize them.

OK, I conditionalized them, and installed the following revised change.

2006-03-27  Paul Eggert  <eggert@cs.ucla.edu>

        * lib-src/b2m.c: Include <limits.h>.
        (TM_YEAR_IN_ASCTIME_RANGE): New macro.
        (main): Check for out-of-range time stamps.
        * lib-src/fakemail.c: Likewise.

--- b2m.c       7 May 2004 15:26:21 -0000       1.30
+++ b2m.c       27 Mar 2006 20:34:18 -0000
@@ -26,6 +26,7 @@
 #undef static
 #endif
 
+#include <limits.h>
 #include <stdio.h>
 #include <time.h>
 #include <sys/types.h>
@@ -44,6 +45,17 @@
 
 typedef int logical;
 
+/* True if TM_YEAR is a struct tm's tm_year value that is acceptable
+   to asctime.  Glibc asctime returns a useful string unless TM_YEAR
+   is nearly INT_MAX, but the C Standard lets C libraries overrun a
+   buffer if TM_YEAR needs more than 4 bytes.  */
+#ifdef __GLIBC__
+# define TM_YEAR_IN_ASCTIME_RANGE(tm_year) ((tm_year) <= INT_MAX - 1900)
+#else
+# define TM_YEAR_IN_ASCTIME_RANGE(tm_year) \
+    (-999 - 1900 <= (tm_year) && (tm_year) <= 9999 - 1900)
+#endif
+
 /*
  * A `struct linebuffer' is a structure which holds a line of text.
  * `readline' reads a line from a stream into a linebuffer and works
@@ -87,6 +99,7 @@ main (argc, argv)
 {
   logical labels_saved, printing, header;
   time_t ltoday;
+  struct tm *tm;
   char *labels, *p, *today;
   struct linebuffer data;
 
@@ -131,7 +144,13 @@ main (argc, argv)
 
   labels_saved = printing = header = FALSE;
   ltoday = time (0);
-  today = ctime (&ltoday);
+  /* Convert to a string, checking for out-of-range time stamps.
+     Don't use 'ctime', as that might dump core if the hardware clock
+     is set to a bizarre value.  */
+  tm = localtime (&ltoday);
+  if (! (tm && TM_YEAR_IN_ASCTIME_RANGE (tm->tm_year)))
+    fatal ("current time is out of range");
+  today = asctime (tm);
   data.size = 200;
   data.buffer = xnew (200, char);
 
--- fakemail.c  6 Feb 2006 11:28:28 -0000       1.35
+++ fakemail.c  27 Mar 2006 20:34:18 -0000
@@ -53,6 +53,7 @@ main ()
 #include "ntlib.h"
 #endif
 
+#include <limits.h>
 #include <stdio.h>
 #include <string.h>
 #include <ctype.h>
@@ -70,6 +71,17 @@ main ()
 #define true 1
 #define false 0
 
+/* True if TM_YEAR is a struct tm's tm_year value that is acceptable
+   to asctime.  Glibc asctime returns a useful string unless TM_YEAR
+   is nearly INT_MAX, but the C Standard lets C libraries overrun a
+   buffer if TM_YEAR needs more than 4 bytes.  */
+#ifdef __GLIBC__
+# define TM_YEAR_IN_ASCTIME_RANGE(tm_year) ((tm_year) <= INT_MAX - 1900)
+#else
+# define TM_YEAR_IN_ASCTIME_RANGE(tm_year) \
+    (-999 - 1900 <= (tm_year) && (tm_year) <= 9999 - 1900)
+#endif
+
 /* Various lists */
 
 struct line_record
@@ -354,6 +366,7 @@ make_file_preface ()
 {
   char *the_string, *temp;
   long idiotic_interface;
+  struct tm *tm;
   long prefix_length;
   long user_length;
   long date_length;
@@ -361,7 +374,13 @@ make_file_preface ()
 
   prefix_length = strlen (FROM_PREFIX);
   time (&idiotic_interface);
-  the_date = ctime (&idiotic_interface);
+  /* Convert to a string, checking for out-of-range time stamps.
+     Don't use 'ctime', as that might dump core if the hardware clock
+     is set to a bizarre value.  */
+  tm = localtime (&idiotic_interface);
+  if (! (tm && TM_YEAR_IN_ASCTIME_RANGE (tm->tm_year)))
+    fatal ("current time is out of range", 0);
+  the_date = asctime (tm);
   /* the_date has an unwanted newline at the end */
   date_length = strlen (the_date) - 1;
   the_date[date_length] = '\0';