[Python-checkins] cpython: Issue #14716: Change integer overflow check in unicode_writer_prepare()

[victor.stinner]

http://hg.python.org/cpython/rev/ab500b297900
changeset:   76821:ab500b297900
user:        Victor Stinner <victor.stinner at gmail.com>
date:        Mon May 07 13:02:44 2012 +0200
summary:
  Issue #14716: Change integer overflow check in unicode_writer_prepare()
to compute the limit at compile time instead of runtime. Patch writen by Serhiy
Storchaka.

files:
  Objects/unicodeobject.c |  6 ++++--
  1 files changed, 4 insertions(+), 2 deletions(-)


diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -13242,8 +13242,10 @@
     newlen = writer->pos + length;
 
     if (newlen > PyUnicode_GET_LENGTH(writer->buffer)) {
-        /* overallocate 25% to limit the number of resize */
-        if (newlen <= (PY_SSIZE_T_MAX - newlen / 4))
+        /* Overallocate 25% to limit the number of resize.
+           Check for integer overflow:
+           (newlen + newlen / 4) <= PY_SSIZE_T_MAX */
+        if (newlen <= (PY_SSIZE_T_MAX - PY_SSIZE_T_MAX / 5))
             newlen += newlen / 4;
 
         if (maxchar > writer->maxchar) {

-- 
Repository URL: http://hg.python.org/cpython