* b2m.c: Include <limits.h>.

[bpt/emacs.git] / lib-src / b2m.c

diff --git a/lib-src/b2m.c b/lib-src/b2m.c
index 5bebe56..adaa736 100644 (file)
--- a/lib-src/b2m.c
+++ b/lib-src/b2m.c
@@ -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);