[base] Tighten the overflow check in `FT_MulFix'.

* src/base/ftcalc.c (FT_MulFix) [!FT_LONG64]: Updated.
10 years ago · 3212852cce
parent 125c3ca8f0
commit 3212852cce
2 changed files with 10 additions and 3 deletions
--- a/6
+++ b/6
@ -1,3 +1,9 @@
+2014-09-03  Alexei Podtelezhnikov  <apodtele@gmail.com>
+
+	[base] Tighten the overflow check in `FT_MulFix'.
+
+	* src/base/ftcalc.c (FT_MulFix) [!FT_LONG64]: Updated.
+
 2014-09-02  Alexei Podtelezhnikov  <apodtele@gmail.com>

 	[truetype] Shortcut ppem calculations for square pixels.
--- a/src/base/ftcalc.c
+++ b/src/base/ftcalc.c
@ -394,7 +394,8 @@
  /*                                                                     */
  /*    a + (b >> 8) <= (131071 >> 4)                                    */
  /*                                                                     */
-  /*  should work well to avoid the overflow.                            */
+  /*  covers the practical range of use. The actual test below is a bit  */
+  /*  tighter to avoid the border case overflows.                        */
  /*                                                                     */

  /* documentation is in freetype.h */
@ -524,7 +525,7 @@
    ua = (FT_ULong)a;
    ub = (FT_ULong)b;

-    if ( ua + ( ub >> 8 ) <= 8191UL )
+    if ( ua + ( ub >> 8 ) <= 8190UL )
      ua = ( ua * ub + 0x8000U ) >> 16;
    else
    {
@ -555,7 +556,7 @@
    ua = (FT_ULong)a;
    ub = (FT_ULong)b;

-    if ( ua + ( ub >> 8 ) <= 8191UL )
+    if ( ua + ( ub >> 8 ) <= 8190UL )
      ua = ( ua * ub + 0x8000UL ) >> 16;
    else
    {