Merged revisions 68589 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r68589 | antoine.pitrou | 2009-01-14 00:13:52 +0100 (mer., 14 janv. 2009) | 5 lines

  Issue #4935: The overflow checking code in the expandtabs() method common
  to str, bytes and bytearray could be optimized away by the compiler, letting
  the interpreter segfault instead of raising an error.
........

Misc/NEWS

@@ -12,6 +12,10 @@ What's New in Python 2.6.2
 Core and Builtins
 -----------------
 
+- Issue #4935: The overflow checking code in the expandtabs() method common
+  to str, bytes and bytearray could be optimized away by the compiler, letting
+  the interpreter segfault instead of raising an error.
+
 - Issue #1180193: When importing a module from a .pyc (or .pyo) file with
   an existing .py counterpart, override the co_filename attributes of all
   code objects if the original filename is obsolete (which can happen if the

Objects/stringlib/transmogrify.h

@@ -22,76 +22,69 @@ stringlib_expandtabs(PyObject *self, PyObject *args)
 {
     const char *e, *p;
     char *q;
-    Py_ssize_t i, j, old_j;
+    size_t i, j;
     PyObject *u;
     int tabsize = 8;
-
+    
     if (!PyArg_ParseTuple(args, "|i:expandtabs", &tabsize))
-	return NULL;
-
+        return NULL;
+    
     /* First pass: determine size of output string */
-    i = j = old_j = 0;
+    i = j = 0;
     e = STRINGLIB_STR(self) + STRINGLIB_LEN(self);
     for (p = STRINGLIB_STR(self); p < e; p++)
         if (*p == '\t') {
-	    if (tabsize > 0) {
-		j += tabsize - (j % tabsize);
-                /* XXX: this depends on a signed integer overflow to < 0 */
-                /* C compilers, including gcc, do -NOT- guarantee this. */
-		if (old_j > j) {
-		    PyErr_SetString(PyExc_OverflowError,
-				    "result is too long");
-		    return NULL;
-		}
-		old_j = j;
+            if (tabsize > 0) {
+                j += tabsize - (j % tabsize);
+                if (j > PY_SSIZE_T_MAX) {
+                    PyErr_SetString(PyExc_OverflowError,
+                                    "result is too long");
+                    return NULL;
+                }
             }
-	}
+        }
         else {
             j++;
             if (*p == '\n' || *p == '\r') {
                 i += j;
-                old_j = j = 0;
-                /* XXX: this depends on a signed integer overflow to < 0 */
-                /* C compilers, including gcc, do -NOT- guarantee this. */
-                if (i < 0) {
+                j = 0;
+                if (i > PY_SSIZE_T_MAX) {
                     PyErr_SetString(PyExc_OverflowError,
                                     "result is too long");
                     return NULL;
                 }
             }
         }
-
-    if ((i + j) < 0) {
-        /* XXX: this depends on a signed integer overflow to < 0 */
-        /* C compilers, including gcc, do -NOT- guarantee this. */
+    
+    if ((i + j) > PY_SSIZE_T_MAX) {
         PyErr_SetString(PyExc_OverflowError, "result is too long");
         return NULL;
     }
-
+    
     /* Second pass: create output string and fill it */
     u = STRINGLIB_NEW(NULL, i + j);
     if (!u)
         return NULL;
-
+    
     j = 0;
     q = STRINGLIB_STR(u);
-
+    
     for (p = STRINGLIB_STR(self); p < e; p++)
         if (*p == '\t') {
-	    if (tabsize > 0) {
-		i = tabsize - (j % tabsize);
-		j += i;
-		while (i--)
-		    *q++ = ' ';
-	    }
-	}
-	else {
+            if (tabsize > 0) {
+                i = tabsize - (j % tabsize);
+                j += i;
+                while (i--)
+                    *q++ = ' ';
+            }
+        }
+        else {
             j++;
-	    *q++ = *p;
+            *q++ = *p;
             if (*p == '\n' || *p == '\r')
                 j = 0;
         }
-
+    
     return u;
 }