Handle overflow when computing char display width (Bug#9496).

* character.c (char_width): Return EMACS_INT, not int.
(char_width, c_string_width): Check for overflow when
computing the width; this is possible now that individual
characters can have unbounded width.  Problem introduced
by merge from Emacs 23 on 2012-01-19.

diff --git a/src/ChangeLog b/src/ChangeLog
index 2667f4c..d6decb7 100644 (file)
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2012-02-03  Paul Eggert  <eggert@cs.ucla.edu>
+
+       Handle overflow when computing char display width (Bug#9496).
+       * character.c (char_width): Return EMACS_INT, not int.
+       (char_width, c_string_width): Check for overflow when
+       computing the width; this is possible now that individual
+       characters can have unbounded width.  Problem introduced
+       by merge from Emacs 23 on 2012-01-19.
+
 2012-02-02  Michael Albinus  <michael.albinus@gmx.de>
 
        * dbusbind.c (Fdbus_register_method): Mention the return value

diff --git a/src/character.c b/src/character.c
index 593fbce..82bc2bf 100644 (file)
--- a/src/character.c
+++ b/src/character.c
@@ -311,10 +311,10 @@ If the multibyte character does not represent a byte, return -1.  */)
 
 /* Return width (columns) of C considering the buffer display table DP. */
 
-static int
+static EMACS_INT
 char_width (int c, struct Lisp_Char_Table *dp)
 {
-  int width = CHAR_WIDTH (c);
+  EMACS_INT width = CHAR_WIDTH (c);
 
   if (dp)
     {
@@ -326,7 +326,12 @@ char_width (int c, struct Lisp_Char_Table *dp)
          {
            ch = AREF (disp, i);
            if (CHARACTERP (ch))
-             width += CHAR_WIDTH (XFASTINT (ch));
+             {
+               int w = CHAR_WIDTH (XFASTINT (ch));
+               if (INT_ADD_OVERFLOW (width, w))
+                 string_overflow ();
+               width += w;
+             }
          }
     }
   return width;
@@ -340,7 +345,8 @@ Tab is taken to occupy `tab-width' columns.
 usage: (char-width CHAR)  */)
   (Lisp_Object ch)
 {
-  int c, width;
+  int c;
+  EMACS_INT width;
 
   CHECK_CHARACTER (ch);
   c = XINT (ch);
@@ -367,10 +373,14 @@ c_string_width (const unsigned char *str, EMACS_INT len, int precision,
     {
       int bytes;
       int c = STRING_CHAR_AND_LENGTH (str + i_byte, bytes);
-      int thiswidth = char_width (c, dp);
+      EMACS_INT thiswidth = char_width (c, dp);
 
-      if (precision > 0
-         && (width + thiswidth > precision))
+      if (precision <= 0)
+       {
+         if (INT_ADD_OVERFLOW (width, thiswidth))
+           string_overflow ();
+       }
+      else if (precision - width < thiswidth)
        {
          *nchars = i;
          *nbytes = i_byte;