[Python-checkins] cpython: Issue #19437: Fix _PyUnicode_New() (constructor of legacy string), set all

[victor.stinner]

http://hg.python.org/cpython/rev/22ce0b7b1eaf
changeset:   86744:22ce0b7b1eaf
user:        Victor Stinner <victor.stinner at gmail.com>
date:        Tue Oct 29 19:31:43 2013 +0100
summary:
  Issue #19437: Fix _PyUnicode_New() (constructor of legacy string), set all
attributes before checking for error. The destructor expects all attributes to
be set. It is now safe to call Py_DECREF(unicode) in the constructor.

files:
  Objects/unicodeobject.c |  35 +++++++++++++++-------------
  1 files changed, 19 insertions(+), 16 deletions(-)


diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -896,22 +896,7 @@
     if (unicode == NULL)
         return NULL;
     new_size = sizeof(Py_UNICODE) * ((size_t)length + 1);
-    _PyUnicode_WSTR(unicode) = (Py_UNICODE*) PyObject_MALLOC(new_size);
-    if (!_PyUnicode_WSTR(unicode)) {
-        Py_DECREF(unicode);
-        PyErr_NoMemory();
-        return NULL;
-    }
-
-    /* Initialize the first element to guard against cases where
-     * the caller fails before initializing str -- unicode_resize()
-     * reads str[0], and the Keep-Alive optimization can keep memory
-     * allocated for str alive across a call to unicode_dealloc(unicode).
-     * We don't want unicode_resize to read uninitialized memory in
-     * that case.
-     */
-    _PyUnicode_WSTR(unicode)[0] = 0;
-    _PyUnicode_WSTR(unicode)[length] = 0;
+
     _PyUnicode_WSTR_LENGTH(unicode) = length;
     _PyUnicode_HASH(unicode) = -1;
     _PyUnicode_STATE(unicode).interned = 0;
@@ -923,6 +908,24 @@
     _PyUnicode_LENGTH(unicode) = 0;
     _PyUnicode_UTF8(unicode) = NULL;
     _PyUnicode_UTF8_LENGTH(unicode) = 0;
+
+    _PyUnicode_WSTR(unicode) = (Py_UNICODE*) PyObject_MALLOC(new_size);
+    if (!_PyUnicode_WSTR(unicode)) {
+        Py_DECREF(unicode);
+        PyErr_NoMemory();
+        return NULL;
+    }
+
+    /* Initialize the first element to guard against cases where
+     * the caller fails before initializing str -- unicode_resize()
+     * reads str[0], and the Keep-Alive optimization can keep memory
+     * allocated for str alive across a call to unicode_dealloc(unicode).
+     * We don't want unicode_resize to read uninitialized memory in
+     * that case.
+     */
+    _PyUnicode_WSTR(unicode)[0] = 0;
+    _PyUnicode_WSTR(unicode)[length] = 0;
+
     assert(_PyUnicode_CheckConsistency((PyObject *)unicode, 0));
     return unicode;
 }

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