(Finsert_file_contents): Fix overflow check to not

depend on undefined integer overflow.

2 files changed, 27 insertions, 21 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index d5edca82fe9..21e1f9c9df2 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2007-12-16  Andreas Schwab  <schwab@suse.de>
+
+        * fileio.c (Finsert_file_contents): Fix overflow check to not
+        depend on undefined integer overflow.
+
 2007-12-14  Jason Rumney  <jasonr@gnu.org>
 
         * w32term.c (w32_read_socket): Use MULTIBYTE_CHAR_KEYSTROKE_EVENT
diff --git a/src/fileio.c b/src/fileio.c
index 2d6f74a8840..dbdeef7076a 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -21,6 +21,7 @@ the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 Boston, MA 02110-1301, USA.  */
 
 #include <config.h>
+#include <limits.h>
 
 #ifdef HAVE_FCNTL_H
 #include <fcntl.h>
@@ -3693,26 +3694,26 @@ read_non_regular_quit ()
 DEFUN ("insert-file-contents", Finsert_file_contents, Sinsert_file_contents,
        1, 5, 0,
        doc: /* Insert contents of file FILENAME after point.
-Returns list of absolute file name and number of characters inserted.
-If second argument VISIT is non-nil, the buffer's visited filename and
-last save file modtime are set, and it is marked unmodified.  If
-visiting and the file does not exist, visiting is completed before the
-error is signaled.
-
-The optional third and fourth arguments BEG and END specify what portion
-of the file to insert.  These arguments count bytes in the file, not
-characters in the buffer.  If VISIT is non-nil, BEG and END must be nil.
-
-If optional fifth argument REPLACE is non-nil, replace the current
-buffer contents (in the accessible portion) with the file contents.
-This is better than simply deleting and inserting the whole thing
-because (1) it preserves some marker positions and (2) it puts less data
-in the undo list.  When REPLACE is non-nil, the second return value is
-the number of characters that replace previous buffer contents.
-
-This function does code conversion according to the value of
-`coding-system-for-read' or `file-coding-system-alist', and sets the
-variable `last-coding-system-used' to the coding system actually used.  */)
+               Returns list of absolute file name and number of characters inserted.
+               If second argument VISIT is non-nil, the buffer's visited filename and
+               last save file modtime are set, and it is marked unmodified.  If
+               visiting and the file does not exist, visiting is completed before the
+               error is signaled.
+
+               The optional third and fourth arguments BEG and END specify what portion
+               of the file to insert.  These arguments count bytes in the file, not
+               characters in the buffer.  If VISIT is non-nil, BEG and END must be nil.
+
+               If optional fifth argument REPLACE is non-nil, replace the current
+               buffer contents (in the accessible portion) with the file contents.
+               This is better than simply deleting and inserting the whole thing
+               because (1) it preserves some marker positions and (2) it puts less data
+               in the undo list.  When REPLACE is non-nil, the second return value is
+               the number of characters that replace previous buffer contents.
+
+               This function does code conversion according to the value of
+               `coding-system-for-read' or `file-coding-system-alist', and sets the
+               variable `last-coding-system-used' to the coding system actually used.  */)
      (filename, visit, beg, end, replace)
      Lisp_Object filename, visit, beg, end, replace;
 {
@@ -3863,7 +3864,7 @@ variable `last-coding-system-used' to the coding system actually used.  */)
              overflow.  The calculations below double the file size
              twice, so check that it can be multiplied by 4 safely.  */
           if (XINT (end) != st.st_size
-              || ((int) st.st_size * 4) / 4 != st.st_size)
+              || st.st_size > INT_MAX / 4)
             error ("Maximum buffer size exceeded");
 
           /* The file size returned from stat may be zero, but data